WO2008052838A1

WO2008052838A1 - Filter element, especially for filtering internal combustion engine emissions

Info

Publication number: WO2008052838A1
Application number: PCT/EP2007/059590
Authority: WO
Inventors: Hans-Peter Frisse; Lars Thuener; Christian Schiller
Original assignee: Robert Bosch Gmbh
Priority date: 2006-11-03
Filing date: 2007-09-12
Publication date: 2008-05-08
Also published as: DE102006051927A1

Abstract

The invention relates to a filter element (18), particularly for filtering internal combustion engine (10) emissions, comprising intake ducts (28) that are open at the intake end and closed at the discharge end in the direction of flow (20), and discharge ducts (30) which are closed at the intake end and open at the discharge end in the direction of flow (20). Said filter element (18) has at least one section (36) in which a space that is large enough for arranging at least one intake duct (28) or at least one discharge duct (30) is filled up with a filling material.

Description

description

Filter element in particular for filtering exhaust gases of an internal combustion engine

State of the art

The invention relates to a filter element, in particular for filtering exhaust gases of an internal combustion engine, according to the preamble of claim 1, and a particulate filter and an exhaust gas purification system with a filter element. The invention further relates to a method for producing a filter element.

The exhaust gas to be cleaned flows through the open-pore filter walls arranged between the inlet channels and the outlet channels. In the process, soot particles are deposited on the upstream surface of the filter walls over time. These soot particles lead to a reduction in the permeability of the filter walls and, as a result, to an increase in the pressure drop which occurs when the gas flow passes through the filter walls. Accordingly, the so-called "exhaust backpressure" increases. If this exceeds a certain value, the filter is regenerated by burning the separated soot particles. For this purpose, the temperature of the exhaust gas, which is passed through the filter element, can be increased. This is effected, for example, by the injection of additional fuel.

During regeneration of the filter element, the temperature distribution within the filter element is such that maximum temperatures occur inside the filter element and lower temperatures occur in the radially outer edge region of the filter element. In addition, the filter element also has an uneven temperature distribution in the axial direction, since the loading of the filter element to be regenerated with particles filtered out from the exhaust gas is uneven in the flow direction of the filter element. During a regeneration process occur in a radially inner region on the downstream side of the Filter element particularly high temperatures. As a result, high temperature gradients occur during the regeneration of the filter element, which causes locally very different thermal expansions, so that high mechanical stresses can occur in the filter element. These stresses can lead to cracking in the filter element in the worst case.

Disclosure of the invention

Object of the present invention is to provide a filter element which is exposed to a regeneration of the smallest possible stress.

The object underlying the invention is achieved in a filter element mentioned above in that the filter element has at least one section in which a sufficiently sized for the arrangement of at least one inlet channel or at least one outlet channel space is filled with a filler.

Advantageous effects

The filter element according to the invention has at least one portion which would be sufficiently large for the arrangement of an inlet channel or an outlet channel, but is filled with a filling material. With the aid of the filling material, it is possible to increase the volume-specific heat capacity of the filter element in the section filled with the filling material. In this way, the heat capacity of the filter element can be influenced locally. By increasing the heat capacity, these areas heat up less rapidly during a regeneration process, so that the temperature gradients that can lead to the above-described mechanical stresses and even cracks are smaller or even completely avoided.

The filling of at least one section of a filter element in a section which would be sufficiently large for an arrangement of an inlet channel or an outlet channel is initially accompanied by a reduction in the available filter area. However, because of the Influencing the local heat capacity of the filter element in a regeneration process occur less high voltages, the filter walls, which limit the inlet channels and outlet channels, have lower wall thicknesses. In this way, the channel density (which is commonly indicated in cpsi, "channels per square inch") can even be increased, although at least one section for disposing of channels is not available because it is filled with filler. By increasing the channel density, an overall higher volume-specific filter surface can be created. As a result, regeneration must be carried out less frequently, which in turn results in lower fuel consumption and an increase in the service life of the filter element.

In an advantageous manner, the filled-up portion is arranged in a radially inner region of the filter element. In this area, the highest temperatures occur during a regeneration of the filter element. By filling this area of the filter element with filling material, the heat capacity in this area is increased, so that a higher amount of energy must be supplied to this area by a certain amount

To heat temperature difference. In this way, the maximum temperature gradients occurring in this area can be reduced.

It when the said portion is arranged coaxially to the longitudinal axis of the filter element is particularly advantageous. This makes it possible to obtain a largely homogeneous temperature distribution in cylindrical filter elements at least in the radial direction.

The dimensions of the filled with filler portion may be selected so that it occupies at least the space of 4, in particular 9, further 16 in particular inlet channels and / or outlet channels. The more space occupies the filled with filler section, the more the heat capacity of the filter element can be increased in total, so that the total occurring during a regeneration process maximum temperature gradient can be reduced.

According to a particularly advantageous embodiment of the invention, the filling material is equal to the material from which the inlet channels and / or the outlet channels defining filter walls are formed. In this way, the filter element can be produced in a particularly simple manner by the extrusion process. In this case, the extrusion tool has a passage on, which corresponds to the cross section of the filled with filler section.

Further advantages and advantageous embodiments of the invention are the following drawings, the description and the claims removable. All features described in the drawing, the description and the claims may be essential to the invention both individually and in any combination.

Brief description of the drawings

Show it:

Figure 1 is a schematic representation of an internal combustion engine with a

Emission control system and with a filter element;

Figure 2 is a longitudinal section of a conventional filter element;

FIG. 3 shows a longitudinal section of a filter element according to the invention;

Figure 4 shows a cross section of the filter element according to Figure 3 and

FIG. 5 is a view corresponding to FIG. 3 for a filter element produced in the extrusion process.

Embodiments of the invention

In Figure 1, an internal combustion engine carries the reference numeral 10. The exhaust gases are fed via an exhaust pipe 12 of an exhaust gas purification system 14. This comprises a particle filter 16, with which soot particles are filtered out of the exhaust gas flowing in the exhaust pipe 12. This is particularly necessary in diesel internal combustion engines to comply with legal requirements. The particulate filter 16 comprises an overall substantially cylindrical filter element 18.

FIG. 2 shows a filter element 18 known from the prior art in a longitudinal section. The filter element 18 may be made, for example, as an extruded molded article of a ceramic material, such as cordierite.

The filter element 18 is flowed through in the direction of the arrows 20 of exhaust gas of the internal combustion engine 10. An inlet surface for the exhaust gas to be filtered carries the reference numeral 22 in FIG. 2 and a filtered exhaust gas outlet surface the reference symbol 24.

Parallel to a longitudinal axis 26 of the filter element 18 extend a plurality of inlet channels 28 and outlet channels 30. The inlet channels 28 are open at the inlet surface 22 and closed at the outlet surface 24. In contrast, the outlet channels 30 are open at the exit surface 24 and closed in the region of the entry surface 22.

The flow path of the uncleaned exhaust gas thus leads into one of the inlet channels 28 and from there via a filter wall 32 into one of the outlet channels 30. This is illustrated by arrows 34 by way of example.

In Figure 3, a filter element according to the invention is designated overall by the reference numeral 18. In contrast to FIG. 2, the filter element 18 according to FIG. 3 is not provided with inlet channels 28 and outlet channels 30 over its entire cross section, but instead has a section 36 in a radially inner region, which can be used to arrange at least one inlet channel 28 and / or at least one outlet channel 30 would be large enough, but filled with filler. The section 36 is substantially cylindrical (see FIG. 4) and is formed of the same material as the partitions 32, for example of cordierite.

In order to force the flow path for exhaust gas to be filtered which is also designated by 24 in FIG. 3, mutually adjacent inlet channels 28 and outlet channels 30 are each provided mutually with sealing plugs 38. These are inserted into the ends of the inlet channels 28 and the outlet channels 30. In the cross section of the filter element 18 shown in FIG. 4, the sealing plugs 38 are not yet inserted. The filter element 18 according to FIG. 4 has the filling material-filled section 36 and a radially outer region indicated overall by the reference numeral 40, in which the inlet channels 28 and the outlet channels 30 are arranged.

The geometry of the filter element 18 shown in cross-section in FIG. 4 can be generated by means of an extrusion process shown schematically in FIG. Here, a strand of material 42 is fed to an extrusion die 44. The extrusion tool 44 has passages, not shown in FIG. 5, wherein a comparatively large passage, which is circular in cross-section, is provided for the section 36 of the filter element 18. With the aid of lattice-shaped passages, the dividing walls 32 can be produced in the radially outer region 40 of the filter element 18.

With the help of the portion 36, the heat capacity can be increased in the radially inner region of the filter element 18. This can during a regeneration process of the

Filter element 18 occurring temperature gradients are reduced. It should be noted that the cell density shown in FIGS. 3 to 4, that is to say the number of inlet channels 28 and the outlet channels 30 per area cross-sectional unit, is comparatively low in order to improve the clarity of the drawing. By increasing the heat capacity in the section 36, however, it is possible to provide an increased number of inlet channels 28 and outlet channels 30 per unit area cross-sectional unit compared with conventional filter elements.

Claims

claims

1. Filter element (18), in particular for filtering exhaust gases of an internal combustion engine (10) in the flow direction (20) on the input side and inlet side closed inlet channels (28) and in the flow direction (20) closed on the input side and outlet side open outlet channels (30), characterized in that the filter element (18) has at least one section (36) in which a space sufficient for the arrangement of at least one inlet channel (28) or at least one outlet channel (30) is filled with a filling material.

2. Filter element (18) according to claim 1, characterized in that the portion (36) is arranged in a radially inner region of the filter element (18).

3. Filter element (18) according to claim 1 or 2, characterized in that the portion (36) is arranged coaxially to the longitudinal axis (26) of the filter element (18).

4. Filter element (18) according to at least one of the preceding claims, characterized in that the dimensions of the portion (36) are selected such that it at least the space of 4, in particular 9, further 16 in particular inlet channels (28) and / or outlet channels (30) occupies.

5. Filter element (18) according to at least one of the preceding claims, characterized in that the material from which the inlet channels (28) and / or the outlet channels (30) defining filter walls (32) are formed, at least partially made of a ceramic or a glass-ceramic material, in particular made of cordierite, aluminum titanate or silicon carbide.

6. Filter element (18) according to at least one of the preceding claims, characterized in that the filler at least partially from a ceramic or a glass-ceramic material, in particular made of cordierite, aluminum titanate or silicon carbide.

7. Filter element (18) according to at least one of the preceding claims, characterized in that the filling material is equal to the material from which the inlet channels (28) and / or the outlet channels (30) defining filter walls (32) are formed.

8. Particle filter (16) with a filter element (18) according to one of the preceding claims.

9. exhaust gas purification system (14), in particular with a particle filter (16), with a filter element (18) according to at least one of claims 1 to 8.

10. A method for producing a filter element (18), in particular a filter element (18) according to at least one of claims 1 to 8, characterized in that the filter element (18) is produced by extrusion.