Filter And Method For Producing A Filter

Abstract

A filter for the purification of exhaust gases of an internal combustion engine includes: a housing that can be flowed through by exhaust gas in an axial direction and has an inflow side and an outflow side; a filter body is formed in the housing from a plurality of filter layers, which filter body can be flowed through by the exhaust gas flowing through the housing. The filter layers are of annular form and are arranged concentrically with respect to one another, wherein, in alternating fashion, two filter layers adjacent to one another in a radial direction are connected to one another in fluid-tight fashion at the inflow side, and two filter layers adjacent to one another in a radial direction are connected to one another at the outflow side.

Claims

1-18. (canceled)

19. A filter for the purification of exhaust gases of an internal combustion engine, comprising: a housing configured to be flowed through by the exhaust gases in an axial direction and having an inflow side and an outflow side; and a filter body arranged in the housing, the filter body comprising a plurality of annular filter layers, the filter body configured to be flowed through by the exhaust gases flowing through the housing, wherein the annular filter layers (2, 16) are arranged concentrically with respect to one another, wherein, in alternating fashion, two annular filter layers (2, 16) radially adjacent to one another are connected to one another in fluid-tight fashion at the inflow side, and two annular filter layers (2, 16) radially adjacent to one another are connected to one another at the outflow side.

20. The filter as claimed in claim 19, wherein the filter body (1) has, in alternating fashion in a radial direction, first flow channels (7, 17) that narrow from the inflow side toward the outflow side and second flow channels (8, 18) that narrow from the outflow side toward the inflow side.

21. The filter as claimed in claim 19, wherein the filter body (1) has an undulating configuration in a section along the central axis (14) of the housing (3, 15), wherein the undulation runs between the inflow side and the outflow side.

22. The filter as claimed in claim 19, wherein the annular filter layers (2, 16) are formed by a metal nonwoven (9).

23. The filter as claimed in claim 19, wherein the annular filter layers (2, 16) have, at end regions facing toward the inflow side and/or at end regions facing toward the outflow side, a fluid-impermeable metal strip (10) that runs in a circumferential direction.

24. The filter as claimed in claim 19, wherein the individual filter layers (2, 16) are formed by metal foils rolled up in annular fashion, wherein the cross-section of the respective filter layers (2, 16) conically narrows or conically widens from the inflow side in the direction of the outflow side.

25. The filter as claimed in claim 19, wherein any two filter layers (2, 16) directly adjacent to one another in a radial direction are connected to one another in fluid-tight fashion at the inflow side or the outflow side.

26. The filter as claimed in claim 25, wherein the filter layers (2, 16) connected to one another in fluid-tight fashion are inserted at an end side into groove-like rings (13), and respective end regions of the filter layers (2, 16) are encompassed by the groove-like rings (13).

27. The filter as claimed in claim 19, wherein, between a seal element (5) is arranged between two filter layers (2, 16) connected to one another in fluid-tight fashion, the seal element (5) being arranged and configured to run in a circumferential direction.

28. The filter as claimed in claim 19, wherein a first filter layer (2, 16) that is outermost in a radial direction is connected at the inflow side in fluid-tight fashion in a circumferential direction to the housing (3, 15), and the first filter layer (2, 16) is connected at the outflow side in fluid-tight fashion in a circumferential direction to a second filter layer (2, 16) directly adjacent in a radial direction toward the center, and the second filter layer (2, 16) is connected at the inflow side in fluid-tight fashion in a circumferential direction to a third filter layer (2, 16) arranged third in the radial direction, wherein this connection arrangement continues as far as an innermost filter layer (2, 16) as viewed in a radial direction, the innermost filter layer being closed off with itself in fluid-tight fashion at the end side at the inflow side or the outflow side.

29. The filter as claimed in claim 19, wherein an undulating spacer element (6) is arranged between two filter layers (2, 16) that are directly adjacent to one another in a radial direction, the undulating spacer element (6) being arranged and configured to run in a circumferential direction.

30. The filter as claimed in claim 19, wherein a radially innermost filter layer (2, 16) is closed off in fluid-tight fashion at the end side toward the inflow side or toward the outflow side, such that the filter layer has a conical basic shape.

31. The filter as claimed in claim 19, wherein the annular filter layers (2, 16) have an undulation running in a circumferential direction of the filter body (1).

32. The filter as claimed in claim 31, wherein radially adjacent ones of the filter layers (2, 16), other than a radially outermost filter layer (2, 16) and a radially innermost filter layer, have the same number of undulation peaks and undulation troughs in a circumferential direction.

33. The filter as claimed in claim 32, wherein the amplitude of the undulation peaks and of the undulation troughs on the filter layers (2, 16) increases, from the outside, inward in a radial direction of the filter body (1).

34. A method for producing a filter as claimed in claim 19, wherein the filter body (1) is formed from the plurality of annular filter layers (2, 16), the method comprising: arranging the plurality of filter layers (2, 16) concentrically with respect to one another; inserting the concentrically arranged filter layers (2, 16), into the housing; winding, in annular fashion, a metal foil, to form the individual filter layers (2, 16); and subsequently pulling the annular metal foils over a conically widening molding element (12), wherein the filter layers (2, 16) which form the filter body (1) are, from the inside outward, pulled in each case a defined distance further over the conically widening molding element (12) to realize conically tapering filter layers (2, 16) with an increasing diameter.

35. The method as claimed in claim 34, wherein the annular filter layers (2, 16) have an undulating form in a circumferential direction, and wherein, as a result of expansion of the annular filter layers (2, 16) on the molding element (12), the amplitude of the undulation decreases to an ever greater extent the further the filter layer (2, 16) is pulled over the molding element (12).

36. The method as claimed in claim 35, further comprising inserting the conically tapering filter layers (2, 16) one inside the other such that those filter layers (2, 16) directly adjacent to one another in a radial direction are arranged alternately with the relatively small cross-sectional area toward the inflow side and toward the outflow side, to achieve an accordion-like construction of the filter body (1), wherein the average cross-section of the filter layers (2, 16) decreases in a radial direction from the outside inward.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be explained in detail in the following on the basis of exemplary embodiments with reference to the drawings, in which:

[0036] FIG. 1 shows a schematic view of the inflow side of the filter body;

[0037] FIGS. 2A and 2B show sectional views through the joint of two filter layers;

[0038] FIG. 3 shows a perspective view of an annular filter layer formed from an undulating metal nonwoven with metal strips at the end sides;

[0039] FIG. 4 shows a view of an annular filter layer as in FIG. 3, wherein the filter layer has been pulled over a conically widening molding element;

[0040] FIG. 5A shows a diagrammatic sketch showing two filter layers that have been inserted into a groove-like ring;

[0041] FIG. 5B shows a groove-like ring which has an undulation in a circumferential direction, which undulation is adapted to the undulation of the annular filter layers;

[0042] FIG. 6 shows a view of a so-called filter bag which has been formed from a filter layer and which forms that filter layer of the filter body which is innermost in a radial direction, and

[0043] FIG. 7 shows a section along the central axis through the housing of the filter, wherein the individual mutually concentrically arranged filter layers are likewise illustrated in section.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0044] FIG. 1 shows a partial detail of a filter body 1. The filter body 1 is formed from a multiplicity of filter layers 2, which are arranged concentrically with respect to one another. The filter layers 2 have a conical profile.

[0045] The arrow 4 illustrates the direction of the exhaust gas flowing through the filter body 1. That filter layer 2 which is outermost in a radial direction is connected directly to the housing wall 3 in a circumferential direction. Between the filter layers 2, in particular at the joints between two mutually adjacent filter layers 2, there is arranged a sealing element (seal) 5 which runs in encircling fashion in a circumferential direction. Such a seal is also arranged at the joint between the outermost filter layer 2 and the housing 3.

[0046] At the inflow side, respective undulating spacers 6 are additionally arranged between the filter layers. The spacers 6 space the mutually adjacent filter layers 2 apart from one another and increase the stability of the filter body 1.

[0047] The conical design of the filter layers 2 and the respectively alternating arrangement of the filter layers 2 such that the end region of the filter layer 2 with the relatively small diameter is arranged alternately toward the inflow side and toward the outflow side give rise to the undulating construction of the filter body 1. In particular, the flow channels 7, which narrow from the inflow side toward the outflow side, and the flow channels 8, which widen from the inflow side toward the outflow side, are formed in this way.

[0048] FIG. 2A shows a section through a joint between two filter layers 2, wherein the filter layers shown have a region 9 composed of a metal nonwoven and a region 10 formed from a fluid-impermeable metal strip. FIG. 2A shows in particular the joint between two mutually directly adjacently arranged filter layers 2.

[0049] In FIG. 2A, the two filter layers 2 abut directly against one another at an acute angle. They can be soldered to one another by means of the application of a solder. Alternatively, use may for example also be made of roll welding methods in order to generate a permanently fluid-tight connection between the two filter layers 2.

[0050] In FIG. 2B, the left-hand filter layer 2 has been folded over the right-hand filter layer 2 at the joint. Here, in particular, the region 10 formed by the metal strip has been bent over the end region of the right-hand filter layer 2. By means of this construction, it is possible for a fluid-tight connection of the filter layers to be realized in a simple manner, because a double-layer configuration is generated in the region of the joint.

[0051] FIG. 3 shows a perspective view of an annular filter layer 2, which is formed from a corrugated metal nonwoven 11. The filter layer 2 has, at the axial end regions, in each case one metal strip 10 running in a circumferential direction, as has already been shown in FIGS. 2A and 2B. Between the metal strips 10, there is arranged a metal nonwoven, 9 which forms the filter material itself.

[0052] The annular filter layer 2 is of conical shape, such that the cross section of one axial end region is smaller than the cross section of the other axial end region.

[0053] FIG. 4 shows the annular filter layer 2 of FIG. 3 while the filter layer is mounted on a molding element 12. The molding element 12 has a cross section that widens conically from the tip. As a result of the filter layer 2 being pushed onto the molding element 12, it is thus possible for the filter layer 2 to assume a conical shaping. The further the filter layer 2 is pushed over the molding element 12 proceeding from the tip, the more intensely the filter layer is expanded. As a result of being pushed onto the molding element 12 to different extents, it is thus possible for filter layers 2 with different diameters at their respective axial end regions to be molded from identical blanks.

[0054] FIG. 5A shows two filter layers 2 which are again formed from a metal nonwoven 9 and a metal strip 10, which are inserted into a groove-like ring 13. The metal strips 10 in particular are inserted into the groove-like ring 13. To realize a fluid-tight connection between the filter layers 2, it is possible for the filter layers 2 to be for example soldered or welded to the groove-like ring 13.

[0055] FIG. 5B shows a perspective view of a groove-like ring 13, which is adapted to the shaping of the undulating filter layers 2 from FIGS. 3 and 4.

[0056] FIG. 6 shows an undulating filter layer 2 that has been deformed to form a bag-like structure. Here, in particular, one axial end region of the filter layer 2 in question has been folded together such that the metal strip 10 lies against itself at multiple points. The filter layer 2 can be closed off in fluid-tight fashion by virtue of the contact points between the individual regions of the metal strip 10 being soldered.

[0057] This so-called filter bag forms specifically the filter layer situated in the center, as viewed in a radial direction of the filter body.

[0058] FIG. 7 shows a section along the central axis 14 through the housing 15 of the filter. Illustrated in the housing 15 are multiple mutually concentrically arranged filter layers 16 formed as undulating annular elements.

[0059] The housing 15 is formed by a ring that delimits the filter body in a radial direction. That filter layer 16 outermost in a radial direction is connected in fluid-tight fashion to the housing 15 in the upper end region of the housing 15, such that no exhaust gas can flow through the filter past the filter layer without being filtered.

[0060] The filter layers 16 all have an undulation running in encircling fashion in a circumferential direction, wherein all of the filter layers 16 aside from the layer innermost in a radial direction have the same number of undulation troughs and undulation peaks. The amplitude of the individual undulations increases in a radial direction from the outside inward. This is achieved by virtue of preferably all of the annular filter layers 16 being produced from the same blank. By virtue of the annular blanks being expanded by a conical molding element, the filter layers 16 firstly obtain their conical shape and secondly obtain their final diameter. The more intensely the filter layers 16 are expanded, the more intensely the undulations are flattened.

[0061] That filter layer 16 outermost in a radial direction practically no longer has an undulation at least at the joint with the housing 15, and can thus be connected to the housing in fluid-tight fashion in a particularly effective manner.

[0062] In the section of FIG. 7, it can be clearly seen that the flow channels 17 at the inflow side, which is, for example, at the top in FIG. 7, narrow with increasing inflow depth. The exhaust gas can, practically along the entirety of the filter layers 16, flow across into the flow channels 18 adjacent to the respective filter layer 16. The flow channels 18 increase from the inflow side toward the outflow side situated at the bottom.

[0063] The section through the filter shows the basically accordion-like construction of the filter body in the housing 15. The filter layer that is innermost in a radial direction has been deformed to form a bag-like element and has been closed off in fluid-tight fashion at one side, such that flow cannot pass through this end region.

[0064] The different features of the individual exemplary embodiments can also be combined with one another. The exemplary embodiments in FIGS. 1 to 6 are in particular not of a limiting nature and serve for illustrating the concept of the invention.

[0065] 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.