PARTICULATE FILTER FOR AN EXHAUST SYSTEM AND METHOD OF MAKING SUCH A PARTICULATE FILTER

Abstract

A particulate filter for an exhaust system includes a housing having an exhaust inlet and an exhaust outlet. Arranged in the housing is a porous filter body which has a closed casing and plural flow passages extending in parallel relationship. The filter body defines a longitudinal center axis and has a conical configuration in relation to the longitudinal center axis, with each of the flow passages defining a longitudinal center axis which extends in parallel relationship to the longitudinal center axis of the filter body.

Claims

1. A particulate filter for an exhaust system, comprising: a housing having an exhaust inlet and an exhaust outlet; and a porous filter body arranged in the housing and including a closed casing and plural flow passages extending in parallel relationship, said filter body defining a longitudinal center axis and having a conical configuration in relation to the longitudinal center axis, with each of the flow passages defining a longitudinal center axis which extends in parallel relationship to the longitudinal center axis of the filter body.

2. The particulate filter of claim 1, wherein the filter body has an inlet side on a side of the exhaust inlet and an outlet side on a side of the exhaust outlet, and further comprising a plurality of plugs to selectively close some of the flow passages on the inlet side or outlet side.

3. The particulate filter of claim 1, wherein the filter body has an inlet side on a side of the exhaust inlet and an outlet side on a side of the exhaust outlet, with the filter body having on the inlet side a cross section which is greater than a cross section on the outlet side so that only some of the flow passages have a length sufficient to extend from the inlet side to the outlet side.

4. The particulate filter of claim 2, wherein the flow passages of a first plurality of the flow passages are closed by plugs on the inlet side, when the outlet side of the flow passages of the first plurality of flow passages remains open.

5. The particulate filter of claim 1, further comprising a restraining element resting against the casing for support of the filter body upon a conical inner wall of the housing.

6. The particulate filter of claim 5, wherein the restraining element is elastic.

7. The particulate filter of claim 1, wherein the filter body is arranged in the housing with clearance in an axial direction.

8. The particulate filter of claim 7, further comprising an end stop to limit the clearance of the filter body in the housing.

9. The particulate filter of claim 1, wherein the flow passages of a first plurality of the flow passages have each a cross section which differs from a cross section of the flow passages of a second plurality of the flow passages.

10. The particulate filter of claim 1, constructed for installation in an exhaust system of a motor vehicle.

11. A method of making a particulate filter for an exhaust system, comprising: forming a porous filter body of conical configuration in relation to a longitudinal center axis thereof with a closed casing and plural flow passages extending in parallel relationship, such that each of the flow passages defines a longitudinal center axis which extends in parallel relationship to the longitudinal center axis of the filter body; forming a housing with an exhaust inlet side and an exhaust outlet side; and placing the filter body in the housing.

12. The method of claim 11, further comprising at least partially closing a selected number of flow passages on the inlet side or outlet side with plugs.

13. The method of claim 12, wherein the filter body has on the inlet side a cross section which is greater than a cross section on the outlet side so that only some of the flow passages have a length sufficient to extend from the inlet side to the outlet side.

14. The method of claim 12, further comprising closing only those flow passages by plugs on the inlet side, when the outlet side of those flow passages remains open.

15. The method of claim 11, further comprising supporting the filter body upon a conical inner wall of the housing by a restraining element resting against the casing.

16. The method of claim 15, wherein the restraining element is elastic.

17. The method of claim 11, further comprising arranging the filter body in the housing with clearance in an axial direction.

18. The method of claim 17, further comprising limiting the clearance of the filter body in the housing by an end stop.

19. The method of claim 11, wherein the flow passages of a first plurality of the flow passages have each a cross section which differs from a cross section of the flow passages of a second plurality of the flow passages.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0026] Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

[0027] FIG. 1 is a longitudinal section of a particulate filter according to the present invention for use in an exhaust system; and

[0028] FIG. 2 is a cross section of the particulate filter.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0029] Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments may be illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

[0030] Turning now to the drawing, and in particular to FIG. 1, there is shown a longitudinal section of a particulate filter according to the present invention, generally designated by reference numeral 1, for use in an exhaust system. The particulate filter 1 includes a housing 2, shown here only in part, and a filter body 3 which is arranged in the housing 2 and is made of porous material. The filter body 3 has a closed casing 4 which may be in the form of a coating and/or realized by appropriately treating the filter body 3. A number of flow passages 5, extending in parallel relation in flow direction of exhaust, are formed in the filter body 3. Only few of the flow passages 5 are shown here by way of example for sake of simplicity. As is readily apparent, the filter body 3 has a conical configuration with respect to its longitudinal center axis 6 and defines two end faces 7, 8 which are connected to one another by the casing 4. FIG. 1 further shows that the end face 7 is sized greater in a radial direction with respect to its longitudinal center axis 6 than the end face 8, so that the surface area of the end face 7 is greater than the surface area of the end face 8.

[0031] The end face 7 of the filter body 3 is situated at an inlet side 9 of the filter body 3 and the end face 8 is situated at an outlet side 10 of the filter body 3. Exhaust flows through the particulate filter 1 and the filter body 3 thereof in a direction of arrow 11. Several of the flow passages 5 on both the inlet side 9 and the outlet side 10 are each snugly closed or sealed by a plug 12. In terms of the inlet side 9, this means that exhaust is unable to enter the respective flow passage 5. When the respective flow passage 5 is closed on the outlet side 10, exhaust is unable to exit the filter body 3 from this flow passage 5. Currently preferred is a closure of all those flow passages 5 either on the inlet side 9 or outlet side 10 by a plug 12 that extend through the entire filter body 3. Arrow 13 indicates hereby, by way of example, a flow of exhaust through the filter body 3. As a result, exhaust is able to enter the open flow passages 5 on the inlet side 9. On the outlet side 10, these flow passages 5 are, however, closed to prevent exhaust from exiting these flow passages 5. As a result, exhaust is forced to migrate through the porous filter body 3 into a flow passage 5 that is open on the outlet side 10. As exhaust migrates through the filter body 3, it is cleaned and, at least substantially freed from unwanted particles before being released into the outside environment.

[0032] As described above, the inlet side 9 of the filter body 3 spans a greater surface area than the outlet side 10. Thus, there are flow passages 5 which extend from the inlet side 9 of the filter body 3 but do not fully extend through the filter body 3 in an axial direction as they are cut off by the casing 4. Advantageously, these types of flow passages 5 remain open at all times on the inlet side 9, so that exhaust entering these flow passages 5 are compelled to at least once, suitably however several times, migrate through the porous filter body 3 until reaching a flow passage 5 that is open on the outlet side 10, as indicated by arrow 14. This results in a superior filtering effect.

[0033] In general, the flow passages 5 extend in a straight line through the filter body 3 and define each a longitudinal center axis 15 which extends in parallel relation to the longitudinal center axis 6 of the filter body 3. Some of the flow passages 5 have hereby a shorter axial dimension than others as a result of the conical configuration of the filter body 3. The longitudinal center axes 15 of the flow passages 5 thus extend perpendicular to the inlet side 9 and/or outlet side 10.

[0034] The filter body 3 is supported in the housing 2 by a restraining element 16 which bears upon the casing 4 and upon a conically inner wall 17 of the housing 2. As a result, the filter body 3 is supported by the restraining element 16 upon the inner wall 17 of the housing 2. The restraining element 16 is elastic and may be embodied in the form of a fiber mat. The restraining element 16 is advantageously fluidtight and rests snugly upon the casing 4 and the inner wall 17 so that exhaust is prevented from flowing between the casing 4 and the inner wall 17 past the filter body 3.

[0035] The filter body 3 is arranged with axial clearance in the housing 2. The clearance is limited at least on one side of the filter body 3, in particular on the inlet side 9, by an end stop 18 in the form of a support ring or supporting grid for example. Such a configuration of the particulate filter 1 has the advantage that an increasingly greater force is applied by exhaust upon the filter body 3, as the exhaust mass flow rate increases, in order to urge the filter body 3 in a direction of the exhaust flow, i.e. in flow direction. The force urges the filter body 3 onto the restraining element 16 and away from the end stop. 18. Thus, the filter body 13 is increasingly moved away from the end stop 18 with increasing exhaust mass flow rate as the force applied by exhaust on the filter body 3 in turn increases.

[0036] At the same time, as the force applied by exhaust increases, the restoring force 16 applied by the restraining element 16 increases on the filter body 3 so that the filter body 3 is urged to seek its initial position. This correlation has also an effect on the sealing action between the restraining element 16 on one hand, and the casing 4 and the inner wall 17, on the other hand. Accordingly, the sealing action increases as the exhaust mass flow rate increases. In addition, the slanted casing 4 as a result of the conical shape of the filter body 3, results in a smooth and gentle conduction of exhaust so that pressure loss of the particulate filter 1 is significantly reduced, when compared to conventional particulate filters.

[0037] FIG. 2 is a cross sectional view of the particulate filter 1. The inlet side 9 and the outlet side 10 of the filter body 3 are depicted and it is readily apparent that the end faces 7 and 8 are each round. The inlet side 9 is defined by a diameter d.sub.1 and the outlet side 10 is defined by a diameter d.sub.2. When smaller exhaust mass flow rates are involved, exhaust enters on the inlet side 9 those flow passages 5 which extend entirely through the filter body 3 in the axial direction. The reason being that these flow passages 5 have a lowest flow resistance. With increasing exhaust mass flow rate, however, increasingly more exhaust enters also those flow passages 5 which extend through the filter body 3 in the axial direction only in part, as described above.

[0038] Provision may be made to divide the flow passages 3 in a first type of flow passages and a second type of flow passages, with the first flow passages having a same cross section and the second flow passages having a same cross section, with the cross section of the first flow passages being different, advantageously smaller, than the cross section of the second flow passages. The first flow passages involve flow passages 5 that extend completely through the filter body 3 in the axial direction, whereas the second flow passages involve flow passages 5 that extend only in part through the filter body 3 in the axial direction.

[0039] While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

[0040] What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: