WO2005059323A1

WO2005059323A1 - Particle filter for the purification of exhaust gases

Info

Publication number: WO2005059323A1
Application number: PCT/DE2004/002193
Authority: WO
Inventors: Stephan Wursthorn; Thomas Hauber; Buenyamin Duru
Original assignee: Robert Bosch Gmbh
Priority date: 2003-12-18
Filing date: 2004-10-02
Publication date: 2005-06-30
Also published as: DE10359574A1

Abstract

The invention relates to a particle filter, for the purification of exhaust gases from self-igniting internal combustion engines, comprising filter pockets (5), having a positive fit connection to an external retainer ring (2) on a front face thereof. The filter pockets (5) are arranged turned at an angle (9) to the radial direction (8), such that a longitudinal extension (7) of the filter pockets (5), in the radial direction, leads to a movement (10) of the inner retainer ring (3) in a tangential direction.

Description

Particulate filter for cleaning exhaust gases

Technical field

Soot particles are contained in the exhaust gas, in particular from non-elongation engines with inhomogeneous mixture formation. These soot particles can damage health. For this grand it is necessary to remove the soot particles from the exhaust gas. This is done through the use of particle filters, which are arranged in the exhaust system of the motor vehicle.

State of the art

Particulate filters as used in the prior art include, for example, individual channels that are closed on one side. As a result, the exhaust gas flowing into the channels on the open side must flow through the filter material. The pores in the filter material are dimensioned so that the particles are retained and adsorbed on the filter material. For example, EP-A-1 256 369 discloses an exhaust gas filter in which a plurality of axial channels are formed by a folded filter medium. The channels are closed on one side. A compact design is achieved by winding up the folded filter medium. The wound filter is accommodated in a housing, so that the outside of the filter lies flush against the housing wall.

Another type of particle filter is known from DE-C-36 37 516. This patent describes filter elements for dust filters which are fastened in a partition between the dust gas and the clean gas side and are surrounded by a housing provided with dust gas entry, clean gas discharge and dust gas discharge. The gases to be cleaned flow through the filter elements from outside to inside. The filtering outer surface of the filter element is made of wedge-shaped cells that are lined up around the central axis of the filter element, which are similar to a tube at their upper end and converge in a star shape at their lower end onto a center line which is arranged in the direction of the individual cell bisectors. A particle filter constructed from filter bags is known, for example, from WO 02/102494 AI. Here, filter surfaces made of sintered metal have filter pockets in a wedge shape, with a pocket opening being assigned to the blunt wedge end. The wedge surfaces as the side walls of the filter pockets run against the wedge end opposite the pocket opening and one of the wedge flanks running between the wedge ends, each in a wedge edge. In relation to the direction of flow of the particle filter, this results in large wedge-shaped spaces on one side that are delimited from one another by adjacent filter pockets. On the other hand, the wedge interiors, which flow over filter surfaces, allow large-scale escape of the gases via pocket openings.

When the particle filter for exhaust gas purification of motor vehicles is in operation, the filter elements clog over time due to the filtered soot. This increases the flow resistance of the filter, which has a negative impact on the performance and fuel consumption of the ner internal combustion engine. For this reason, the filter elements must be cleaned regularly. This is done by heating, which burns the adsorbed soot particles.

The filter elements expand due to the high temperatures that occur during cleaning. To ensure that no additional tension occurs due to the strong heating of the filter pockets during regeneration, the end opposite the side attached to the housing is not connected to the housing. The individual filter bags are only connected by a support ring. The particle filter can be excited to vibrate during operation of the motor vehicle. This can lead to an additional high load at the connection points.

A particle filter as used in the prior art comprises filter bags which are connected to an inner retaining ring and an outer retaining ring. The filter bags have side walls that are made of sintered metal. To clean the exhaust gas from internal combustion engines, the exhaust gas flows through the side walls made of sintered metal. The particles contained in the exhaust gas, mainly soot particles, are retained by the porous side walls.

In order to achieve the largest possible filter area in a specific housing, the filter pockets are arranged in a star shape. The side walls of the filter bags run radially from the inner retaining ring to the outer retaining ring. In the case of the particle filters known from the prior art, the filter bags have an open end face through which the exhaust gas usually flows out.

The individual filter bags are connected to the outer retaining ring and the inner retaining ring on the outlet side. The connection is preferably made by welding.

The connection between the outer retaining ring and the filter bags must be tight during the entire operating time of the particle filter to ensure that the exhaust gas flows through the side walls made of porous sintered metal.

Due to the particles retained during operation, the particle filter clogs up over time. The particles are preferably soot. In order to keep the flow resistance of the particle filter as low as possible, the soot deposits have to be removed from time to time. This is preferably done by thermal regeneration. Here, the particle filter is brought to such a high temperature that the soot particles burn. These high temperatures cause the filter bags to expand considerably in both the axial and radial directions.

Due to the longitudinal expansion of the filter bags in the radial direction, stresses occur at the weld seams of the filter bags on the outer retaining ring. These tensions cause cracks to form on the weld seams during the operating time of the particle feeder. The cause of the crack formation is to be seen in the fact that the outer retaining ring expands less than the filter bags.

The cracks initially lead to the connection of the filter bags with the outer retaining ring becoming unstable, furthermore exhaust gas can flow through the cracks and is therefore no longer cleaned of particles contained therein.

Presentation of the invention

A particle filter designed according to the invention for cleaning exhaust gases from internal combustion engines comprises filter bags which are connected in a form-fitting manner on one end face to an outer retaining ring and an inner retaining ring. The filter bags are arranged rotated at an angle of preferably more than 10 ° to the radial position such that an elongation of the filter bags in the radial direction leads to a movement of the inner retaining ring in the tangential direction. Here, the inner retaining ring rotates until the longitudinal expansion of the filter bags is balanced. In a preferred embodiment of the particle filter, the filter bags are made of sintered metal. Here, the exhaust gas flows through porous walls made of sintered metal, particles contained in the exhaust gas being separated off on the sintered metal walls. The sintered metal walls are preferably made from a wire mesh, which has an open cross section of more than 60%. A sintered metal layer is applied to the wire mesh, which is sintered together with the wire mesh.

The filter bags are preferably welded to the outer retaining ring. A gas-tight connection between the individual filter bags and the outer retaining ring is hereby achieved. The gas-tight connection between the filter bags and the outer retaining ring is required so that all of the exhaust gas flows through the sintered metal walls of the filter bags.

In a preferred embodiment, the particle filter designed according to the invention is fastened in a housing. The particle filter is preferably fixed in the housing by screwing the outer retaining ring to the housing.

The side walls of the filter bag which extend from the inner retaining ring to the outer retaining ring can either be straight or curved. The filter bags have a triangular cross-section in the case of straight side walls, and the filter bags have a crescent-shaped cross-section in the case of curved side walls.

drawing

The invention is described in more detail below with reference to a drawing.

It shows:

FIG. 1.1 shows a top view of the outflow side of a particle filter manufactured according to the prior art,

FIG. 1.2 shows a top view of the outflow side of a particle filter designed according to the invention with straight side walls of the filter pockets,

FIG. 2 shows a plan view of a section of the inflow side of a particle filter designed according to the invention with curved side walls of the filter pockets,

FIG. 3 shows a section through a particle filter with a housing, Figure 4 is a perspective view of a filter bag.

variants

FIG. 1.1 shows a top view of the outflow side of a particle filter manufactured according to the prior art.

A particle filter 1 comprises filter pockets 5, which are connected at one end to an outer retaining ring 2, which is preferably designed as a flange, and an inner retaining ring 3. The filter pockets 5 are preferably open on the end face with which the filter pockets 5 are connected to the outer retaining ring 2 and the inner retaining ring 3. For this purpose, spacer plates 8 are accommodated in the filter pockets 5, which are preferably designed in the form of a corrugated plate.

The filter bags 5 are preferably connected to the outer retaining ring 2 and the inner retaining ring 3 in a form-fitting manner, e.g. by welding.

The filter bags 5 have side walls 6, which are preferably made of a sintered metal. The sintered metal is a porous material through which the exhaust gas from the internal combustion engines flows. A high-temperature-resistant wire mesh with an open cross-section of more than 60% is preferably used to manufacture the side walls 6, to which a high-temperature-resistant, porous sintered metal layer is applied and sintered together with the wire mesh. The pore size of the side walls 6 made of sintered metal is selected so that particles contained in the exhaust gas, especially soot particles, are retained. As a result, the exhaust gas is cleaned of the particles contained therein.

The particle filter 1 is preferably accommodated in a housing (not shown in FIG. 1.1). The connection of the particle filter 1 to the housing is preferably non-positively via the outer retaining ring 2 designed as a flange. For this purpose, in a preferred embodiment, 2 holes 4 are made in the outer retaining ring, through which the particle filter 1 is screwed to the housing.

Due to the particles retained by the side walls 6 made of porous sintered metal, the particle filter 1 clogs up during operation. The particle filter 1 must be cleaned from this Grand at regular intervals. The particles are preferably cleaned thermally at high temperatures. As a result, the retained soot particles burn. The high ones that occur during thermal regeneration Temperatures lead to a longitudinal expansion 7 of the side walls 6 of the filter bags 5. Because the outer retaining ring 2 is screwed to the housing, not shown here, and thus has contact with the environment, to which heat is emitted from the outer retaining ring 2 and the housing the outer retaining ring 2 is less open than the filter pockets 5. As a result, the extension of the filter pockets 5 is greater than the elongation of the outer retaining ring 2, which leads to the fact that at the connection points with which the filter pockets 5 are connected to the outer retaining ring 2 tensions occur.

Even during operation, the outer retaining ring 2 is colder than the filter pockets 5, as a result of which the filter pockets 5 have a greater thermal expansion than the outer retaining ring 2.

The different thermal expansions of the filter pockets 5 and the outer retaining ring 2 lead to tensions at the connection points between the filter pockets 5 and the outer retaining ring 2, which can result in cracking. Cracks between the filter bags 5 and the outer retaining ring 2 cause exhaust gas to flow directly over the cracks and not through the filter bags 5. This leads to a reduction in the cleaning performance of the particle filter 1, since the entire exhaust gas no longer flows through the filter bags 5 and thus the exhaust gas is only partially or no longer cleaned.

FIG. 1.2 shows a top view of the outflow side of a particle filter designed according to the invention with straight side walls of the filter pockets.

In order to reduce the stresses acting on the connection point of the filter pockets 5 with the outer retaining ring 2, the filter pockets 5 in the particle filter 1 designed according to the invention are rotated by an angle 9 to the radial direction. The angle 9 is preferably greater than 10 °.

Due to the rotation of the filter pockets 5 by the angle 9, the longitudinal expansion 7 of the side walls 6 of the filter pockets 5, due to the heating and the thermal expansion caused thereby, causes the inner retaining ring 3 to be impressed with a movement in the tangential direction identified by the reference number 10. Here, the inner retaining ring 3 rotates until the longitudinal expansion 7 of the side walls 6 of the filter bags 5 is balanced. The movement 10 of the inner retaining ring 3 in the tangential direction means that no stresses occur at the weld seams with which the filter bags 5 are fastened to the outer retaining ring 2 and crack formation is thus avoided. As a result, the life of the particle filter 1 is increased. An increase in the angle 9 leads to an improved implementation of the longitudinal expansion 7 in the movement supply 10 of the inner retaining ring 3 in the tangential direction. As soon as the filter bags 5 cool and the side walls 6 shorten again, the inner retaining ring 3 also rotates back into the starting position.

An arrangement as shown in Figure 1.2, rotated clockwise to the radial position of the filter bags 5 leads to a longitudinal expansion 7 of the side walls 6 of the filter bags 5 to a movement 10 of the inner retaining ring 3 counterclockwise to compensate for the longitudinal expansion 7. An arrangement of the filter pockets 5 which is rotated counterclockwise to the radial position, on the other hand, leads to a movement 10 of the inner retaining ring 3 in a clockwise direction in order to compensate for the longitudinal expansion 7 of the side walls 6 which occurs due to the thermal expansion when the filter pockets 5 are heated.

Another advantage, which results from the arrangement of the filter bags 5 rotated by the angle 9, is that with the same size of the outer retaining ring 2 and the inner retaining ring 3 as in the arrangement with radially arranged filter pockets known from the prior art , the filter area is increased while the filter volume remains the same.

FIG. 2 shows a section of a plan view of the upstream side of a particle filter designed according to the invention with curved side walls of the filter bags.

In addition to the embodiment shown in FIG. 1.2 with straight side walls 6 of the filter pockets 5, the filter pockets 5 can also have curved side walls 11. Even in the case of curved side walls 11, a longitudinal expansion 7 of the side walls 11 leads to a movement 10 of the inner retaining ring 3 in the tangential direction until the longitudinal expansion 7 is compensated, as a result of which the stresses on the connection of the filter bags 5 to the outer retaining ring 2 are reduced. Another advantage of the curved side walls 11 can be seen in the fact that the filter surface is further enlarged compared to straight side walls 6 with the same diameter of the inner retaining ring 3 and the outer retaining ring 2.

The filter pockets 5 are closed on the upstream side. This ensures that the exhaust gas has to flow through the side walls 11 of the filter pockets 5. The filter bags 5 on the upstream side are preferably closed by roller welding. For this purpose, a side wall 11, 6 is first folded around the other side wall 11, 6 of the filter bag 5. Then the side walls 6, 11 are welded together at the fold 12. On the side facing a cavity 15 in the interior of the particle filter 1, the filter pockets 5 are also closed at a connection point 14. The connection point 14 is also preferably produced by roll welding. Here, too, one side wall 11, 6 of the filter bag 5 is folded around the other side wall 11, 6 of the filter bag 5 and then welded.

So that no exhaust gas can flow through between the individual filter pockets 5 on the outflow side, the filter pockets 5 are connected to one another on the outflow side along the side walls 11, 6. The connection is identified by reference number 13. Here, too, a tight connection of the individual filter pockets 5 to one another is preferably obtained by welding.

On the upstream side, the filter bags 5 are held in position by a support ring 16, which runs along the outside of the filter bags 5.

FIG. 3 shows a section through a particle filter with a housing designed according to the invention.

The particle filter 1 is accommodated in a housing 19 through which the exhaust gas generated by the internal combustion engine flows. The direction of flow of the particle filter is indicated by arrow 17. The exhaust gas reaches the outer sides of the side walls 11, 6 of the filter bags 5, flows through the side walls 6, 11, as a result of which it is cleaned of particles contained in the exhaust gas, and exits the filter bags 5 again on the side facing the outer retaining ring 2. The outflow direction of the exhaust gas from the housing 19 is indicated by the arrow 18.

In order to be able to mount the particle filter 1 in the housing 19, a flange 21 is formed on the housing 19. The housing 19 is closed with a housing cover 20 on which a flange 22 is formed. The flange 21 of the housing 19, the outer retaining ring 2 of the particle filter 1 and the flange 22 of the housing cover 20 are screwed together along the bores 3. Preferably, there are sealing rings between the flange 21 and the outer retaining ring 2 and the outer retaining ring 2 and the flange 22. This ensures that no exhaust gas can escape at the connection between the housing 19, the particle filter 1 and the housing cover 20.

So that no exhaust gas can flow out through the cavity 15 without being passed through the filter pockets 5, the cavity 15 is closed on the outflow side by the inner retaining ring 3. A perspective view of an individual filter bag is shown in Figure 4.

A filter bag 5 is identified here on the inflow side by the inflow direction 17, closed on the side facing the filter center and on the outside 23. The filter bag 5 is open on the outflow side, here identified by the outflow direction 18. In the case of filter bags 5 with straight side walls 6, this results in a triangular cross section on the outflow side. In the case of filter bags with curved side walls 11, the cross section on the outflow side is crescent-shaped.

The outside 23 of the filter bag 5 is also triangular. In order to keep the filter bag 5 open on the outflow side, a spacer plate 8 is accommodated in the filter bag 5. The spacer sheet 8 is preferably in the form of a corrugated sheet. In a preferred embodiment, the filter bag 5 is made of a high-temperature-resistant wire mesh with an open cross section of preferably more than 60%. A high-temperature-resistant sintered metal layer is applied to the wire mesh, which is sintered together with the wire mesh. This material is bent into the shape of the filter bag 5: a fold is formed at the connection point 14, on which the filter bag 5 is preferably closed by roller welding. A fold 12 is formed on the inflow side for closing. The filter bag 5 is then also preferably closed along the fold 12 by roller welding. In order to keep the filter bag 5 open on the outflow side, the spacer plate 8 is inserted into the filter bag 5. In order to connect the individual filter pockets 5 to form the particle filter 1, the filter pockets 5 are connected to one another in a form-fitting manner, preferably by welding, along the upper edge 24.

The arrangement of the filter bags 5 according to the invention to avoid stresses at the junction of the filter bags 5 with the outer retaining ring 2 is particularly suitable for all metallic filters in which the filter surfaces are connected to a flange or to a housing.

LIST OF REFERENCE NUMBERS

Particle filter outer retaining ring inner retaining ring hole filter bag straight side wall expansion direction spacer plate angle movement of the inner retaining ring 3 in the tangential direction curved side wall fold connection of the filter bags on the outflow side connection point cavity support ring inflow direction outflow direction housing housing cover flange of the housing 19 flange of the housing cover 20 outside of the filter pocket 5 top edge

Claims

claims

1. Particulate filter for cleaning exhaust gases of self-igniting internal combustion engines, comprising filter pockets (5) which are positively connected on one end face to an outer retaining ring (2) and an inner retaining ring (3), characterized in that the filter pockets (5) are such are arranged rotated at an angle (9) to the radial position (8) such that a longitudinal expansion (7) of the filter pockets (5) in the radial direction leads to a movement (10) of the inner retaining ring (3) in the tangential direction.

2. Particulate filter according to claim 1, characterized in that the angle (9) is at least 10 °.

3. Particulate filter according to one of claims 1 or 2, characterized in that an arrangement of the filter pockets (5) rotated clockwise to the radial position for a movement (10) of the inner retaining ring (3) counterclockwise and counterclockwise to the radial Twisted arrangement of the filter tabs (5) leads to a movement (10) of the inner retaining ring (3) in a clockwise direction.

4. Particulate filter according to one of claims 1 to 3, characterized in that the filter bags (5) are made of sintered metal.

5. Particulate filter according to one of claims 1 to 4, characterized in that the filter bags (5) are welded to the outer retaining ring (2).

6. Particle filter according to one of claims 1 to 5, characterized in that the particle filter (1) with the outer retaining ring (2) is fixed in a housing (19, 20).

7. Particle filter according to spoke 6, characterized in that the particle filter (1) with the housing (19, 20) is screwed.

8. Particulate filter according to one of claims 1 to 7, characterized in that the filter bags (5) have straight side walls (6).

9. Particulate filter according to one of claims 1 to 7, characterized in that the filter bags (5) have curved side walls (11).

10. Particulate filter according to one of claims 1 to 9, characterized in that the filter bags (5) are closed on the inflow side and on the side pointing towards the center.

11. Particle filter according to one of claims 1 to 10, characterized in that a spacer plate (8) is inserted into the filter pockets (5).

12. Particulate filter according to spoke 11, characterized in that the spacer plate (8) is formed in a corrugated plate.