WO2007025959A1

WO2007025959A1 - Particulate filter with a device for preventing the filter from becoming clogged

Info

Publication number: WO2007025959A1
Application number: PCT/EP2006/065763
Authority: WO
Inventors: Ralf Wirth; Manfred Duernholz; Carsten Becker; Heinrich Duetsch
Original assignee: Robert Bosch Gmbh
Priority date: 2005-08-30
Filing date: 2006-08-29
Publication date: 2007-03-08
Also published as: DE102005040919A1

Abstract

The invention relates to a particulate filter, particularly for exhaust gas of a self-ignition internal combustion engine, comprising an inner tube (12) and a flange (14) with fastening openings (16). A filter body (30) is provided with flow channels (38) and is flowed through in a longitudinal direction (42) by exhaust gas. The filter body (30) contains, in the outer peripheral area, a bypass layer (46) with flow channels (38).

Description

Particulate filter with device for preventing filter blockage

The invention relates to a particulate filter, in particular a particulate filter for exhaust gas from self-igniting internal combustion engines, which is equipped with a device for preventing the filter blockage.

State of the art

Retrofitting solutions for particulate filters, in particular for diesel particulate filters in the automotive sector are known from the prior art. These systems can be designed, for example, as CRT® systems (CRT® continuously regenerating trap), which are already used in buses in public transport. These CRT® systems are not actively regenerated, but are continuously regenerated via the passive NC> ₂ effect. In contrast, active regeneration would mean that exhaust gas temperature-increasing measures would be triggered in the engine control unit.

In systems that continuously use the passive NC> ₂ effect, the vehicles are mainly operated in the operating range with exhaust gas temperatures between 250 ⁰ C to 450 ⁰ C. If the temperatures are lower, which is commonplace in frequent stop-and-go traffic in city traffic, for example, the particulate filter blocks with soot so that the vehicle can no longer be moved.

As an alternative to CRT® systems today, soot filter kits (Twin-Tec or City-Filter) are used. In both solutions, the particle-laden exhaust gas of self-igniting

Internal combustion engines - in contrast to the CRT® system - a bypass offered by which the soot-laden exhaust gas can flow freely to the outside. Therefore, these systems can be a by-pass for the particle-laden exhaust system under unfavorable

Boundary conditions, such as occur in city traffic, for example, are not blocked by soot particles. Thus, the system costs are considerably lower, since a regeneration management is eliminated. However, these systems with a bypass for the particle-laden exhaust gas have the disadvantage that due to the cross-section of the bypass, the filter separation of such particulate filter is considerably lower.

Both the CRT® system and the above-described bypass system are regenerated via the NC> ₂ effect. A Rußabbrand on O ₂ requires temperatures above 600 ⁰ C and can be realized especially in an underfloor arrangement of a particulate filter such as a diesel particulate filter on a motor vehicle only near the Volllastbe- operating state of the internal combustion engine.

Presentation of the invention

The object of the present invention is to provide a particle filter which has a bypass option for the particle-laden exhaust gas which does not or only insignificantly influences regenerative soot burn-up.

According to the invention, it is proposed to design a particle filter in such a way that the essentially cylindrically shaped particle filter has in its outer peripheral region a ring-shaped bypass surface formed by flow channels, which surrounds the filter channels serving to filter the particle-laden exhaust gas stream in an annular manner.

This solution can prevent blocking of a particulate filter, such as a particulate filter for exhaust gas of self-igniting internal combustion engine in city traffic, where there are frequent stop-and-go situations. The exhaust gas is provided to a bypass, whereby it can flow through the particle filter proposed according to the invention, without a higher temperature region occurring soot combustion, whether by O ₂ or either by NO _2, to obstruct.

The bypass layer proposed according to the invention, which can be used in particular on an exchangeable particle filter for vehicle retrofits, lies in a colder region of the particulate filter with regard to the process temperatures occurring. The bypass layer, via which particulate-laden exhaust gas, which does not adversely affect the interior of the particulate filter, can be passed through the particulate filter, flows into a colder region of the particulate filter with regard to the temperatures which occur. The prevailing inside the particulate filter, higher process temperatures, which are between 300 ⁰ C to 450 ⁰ C, allow Rußabbrand in the inner region of the particulate filter. drawing

With reference to the drawing, the invention will be described below in more detail.

It shows:

FIG. 1 shows a perspective view of a particle filter having particle pockets, known from the prior art,

Figure 2 is a plan view of a removed from a canning ceramic filter cartridge of a particulate filter and

FIG. 3 shows an enlarged illustration of a particle body having flow channels with flow channels which form the bypass layer and flow channels which form the filter layer.

embodiments

In the illustration of Figure 1, a particulate filter 10 can be seen, as it is used in particular for retrofitting of buses in public transport. The particle filter 10 shown in a schematic view in FIG. 1 comprises an inner tube 12 which extends in the axial direction through the particle filter 10. On one side of the particle filter 10, a flange 14 is received, which has a number of holes 16 for fastening the particle filter 10 in the exhaust gas tract of a self-igniting internal combustion engine. From the perspective view of Figure 1 shows that a plurality of filter pockets 18 are arranged side by side on the inner tube 12 of the particulate filter 10 in the circumferential direction. Lying in the inflow plane of the particle filter 10, a plurality of joining seams 22 are shown, with which the particle pockets 18 are mutually connected. The longitudinal extent of the particulate filter 10, the inner tube 12 and the filter pockets 18 is indicated by reference numeral 20.

In the case of the particle filter shown in FIG. 1, an outflow pipe lies coaxially with the inner pipe 12 according to FIG. 1 and thus at a point within the particle filter 10 at which the highest process temperatures occur. Thus, the particulate filter 10 shown in Figure 1 has the serious disadvantage that the particle-laden exhaust stream leaves the particulate filter 10 at a bypass point, namely the outflow pipe, where, however, with respect to temperature optimal conditions for Rußabbrand prevail by O ₂ or NO ₂ . -A-

The illustration according to FIG. 2 shows a plan view of a ceramic honeycomb body 30, the upstream side 36 of which flows through a particle-laden gas stream. The longitudinal extension of the honeycomb body 30 according to FIG. 2 is identified by reference numeral 42. The illustration according to FIG. 2 shows that the ceramic honeycomb body 30 is surrounded by an intermediate layer 44. At the ends of the intermediate layer 44, in the region of the end faces of the ceramic honeycomb body 30, flow channels 38 of the bypass layer 46 are exposed, which cover those of the flow channels 38 which lie further in the center of the ceramic honeycomb body 30.

FIG. 3 shows, in an enlarged view, a detail of a circular quarter of a ceramic honeycomb body 30, as shown in FIG. 2 in plan view.

The illustration according to FIG. 3 shows that the ceramic honeycomb body 30 has a filter jacket surface 32. In its outer region 34, the ceramic honeycomb body 30 - which is formed substantially cylindrical - a bypass layer 46. With respect to the axis of symmetry of the ceramic honeycomb body 30 as shown in Figure 3, the bypass layer 46 has an outer diameter d ₂ , which the internal diameter of the Filtermantelfiäche 32 corresponds. Also concentric with the axis of symmetry, the ceramic honeycomb body 30 includes a number of flow channels 38 which extend into the plane of the drawing forming a filter layer 48. The filter layer 48 has an outer diameter di with respect to the axis of symmetry of the ceramic honeycomb body 30 of the particulate filter 10. Half the difference between the diameter d _{2 of} the filter cladding surface 32 and the outer diameter di of the filter layer 48 defines the thickness of the by-pass layer 46 ((d2 - di) / 2). The likewise flow channels 38 having bypass layer 46 includes flow channels 38, which are without flow obstruction, ie without plugs (plugs) are formed. As a result, the flow resistance in the flow channels 38 within the bypass layer 46 is substantially less than the flow resistance within the filter layer 48 formed by the flow channels. The flow channels 38 which lie within the filter layer 48 are mutually closed with plugs or plugs, so that the Particle-laden exhaust gas is forced to penetrate through the channel walls 40 of the flow channels 38. In the process, the particles contained in the particle-laden exhaust gas are deposited in these channel walls 40.

Corresponding to the diameter difference between the diameter d _{2 of} the filter jacket surface 32 minus the diameter di of the filter layer 48, a bypass layer 46 results from flow channels 38, from which the plugs or the plugs are removed. The bypass layer 46 advantageously extends on the outer circumference of a ceramic honeycomb body 30 and is enclosed by the Filtermantelfiäche 32. In this area With respect to the temperature inside the particulate filter 10, colder temperatures prevail. By inventively proposed solution to create a bypass layer 46 on the Außenmantelfiäche a ceramic honeycomb body 30 of a particle body 10, the Rußabbrand inside, ie not affected in the region of the inner tube 12 of the particulate filter 10. This creates a bypass possibility for the particle-laden exhaust gas, in order to avoid the blocking of a particle filter 10, which lies in relation to the particle filter 10 where its temperatures are coldest.

The solution proposed according to the invention ensures that the soot burn in the region of the inner tube 12, which passes through the particle filter 10 in the axial direction along its longitudinal extension 42, is not prevented by blocking the flow channels 38 in the form of a bypass layer 46. Channel is affected. By prevailing in the interior of the particulate filter 10 temperatures between 250 ⁰ C and 450 ⁰ C, a continuous Rußabbrand is ensured in the interior of the particulate filter 10, which is not affected by the bypass layer 46.

Claims

claims

1. particulate filter, in particular for exhaust gases of a self-igniting internal combustion engine, with a filter body (30) with flow channels (38) through which the exhaust gas in the longitudinal direction (20), characterized in that the filter body (30) in the outer peripheral region of a bypass layer ( 46) with flow channels (38).

2. Particulate filter according to claim 1, characterized in that the filter body (30) is a ceramic honeycomb body.

3. Particle filter according to claim 1, characterized in that the filter body (30) contains a filter layer (48) with mutually closed flow channels (38) which is enclosed by the bypass layer (46).

4. Particle filter according to claim 1, characterized in that the bypass layer (46) is designed in a diameter d ₂ , which corresponds to an inner diameter of a filter lateral surface (32).

5. Particle filter according to claims 3 and 4, characterized in that the filter layer (48) is designed in a diameter di which is smaller than the diameter d _{2 of} the bypass layer (46).

6. Particle filter according to claim 1, characterized in that the flow channels (38) of the bypass layer (46) can be flowed through freely by the exhaust gas.

7. Particle filter according to claim 1, characterized in that the filter body (30) is received on a through the particulate filter extending inner tube (12).

8. Particulate filter according to one of the preceding claims, characterized in that it has a flange (14) with fastening openings (16).

9. filter body for filtering exhaust gases, in particular a self-igniting internal combustion engine, b with flow channels (38), wherein the filter body from the exhaust gas in the longitudinal direction (20) is flowed through, characterized in that the filter body (30) in the outer peripheral region of a bypass layer (46) with flow channels (38) contains.