DE102007003121A1 - Particulate filter, particularly exhaust gas -particulate filter for internal combustion engine, has comb-like filter body, in which alternating and overall processing of input channel and output channel are provided - Google Patents

Abstract

The particulate filter has a comb-like filter body (18), in which alternating and overall processing of input channel and output channel are provided in the longitudinal direction and has a radial external shell, which comprises of fibers. The fibers are brought in during or after the extrusion in the green part of the filter body. Some of the fibers consist of spun fiber yarn. The filter body is made up of ceramic material, for example cordierite, with fibers manufactured from ceramic material, particularly carbon, aluminum oxide and silicon oxide.

Description

State of the art

The The invention relates to a particulate filter, in particular an exhaust gas particulate filter for an internal combustion engine according to the preamble of claim 1.

Such a particle filter is from the DE 101 30 338 A1 known. This is a ceramic honeycomb filter having in a filter body a plurality of honeycomb channels extending generally in the longitudinal direction of the filter body. These are alternately closed at their upstream end, ie in the region of an inlet side of the filter body or at the downstream end, ie in the region of an outlet side of the filter body, by closing sections. As a result, individual pocket-like honeycomb are formed. Between the individual channels, porous filter walls are arranged, through which the exhaust gas flow passes during operation. Soot particles are thereby separated from the exhaust gas. On its radial outer side, the filter body has a usually circular cylindrical jacket, which closes the filter body radially outward.

The separated soot particles lead to a reduction the permeability of the filter walls and consequently to an increase in pressure drop when passing the exhaust gas flow through the filter walls occurs. Corresponding increases the so-called "exhaust backpressure". To the efficiency keep the internal combustion engine high, the particulate filter of Regenerated time by time by the deposited soot particles oxidized, so burned. In this exothermic oxidation reaction is Heat released, which leads to high peak temperatures can lead inside the filter body.

Disclosure of the invention

task the present invention is to provide a particulate filter which has the longest possible life.

These The object is achieved by a particle filter having the features of the claim 1 solved. Advantageous developments are in subclaims specified. Important features are also found also in the following description and the drawing, wherein these features for the invention in isolation or in very different combinations can be essential without being explicitly pointed out.

According to the invention was recognized that at a regeneration between the radial Center and the radial edge, there in particular the jacket of the filter body can form high spatial temperature gradients, since the heating of the radial center is stronger as those of the radial rim. The uneven temperature distribution has an uneven thermal expansion of the filter body resulting in the build-up of stresses leads in the filter body. The maximum tensile stresses occur in the lateral surface of the filter body. These have their cause in that the strain of the radially inside lying region of the filter body by the outer Region and the mantle is obstructed. In addition, the coat of a Filter body then, when the thickness of the shell larger is the thickness of the walls between the inlet channels and the outlet channels, a strong jump in stiffness represents.

By the measure according to the invention, in the Incorporating material fibers increases the strength of the shell. This reduces the risk that the jacket will fail due to a "ring-off crack". Through the fibers, the strength of the shell over that Improved measure, which is to compensate for expected increase in tension is required. Ultimately So is the inventive measure the thermomechanical stability of the particulate filter and thus its reliability over its lifetime improved. The life is extended and the maximum permissible load is increased. This in turn allows the design of the particulate filter such that it has a lower Exhaust back pressure has, or that the intervals between two successive regenerations are increased or that the duration of a regeneration is reduced by a higher one Regeneration temperature is allowed. This in turn allows a reduction of that required for regeneration additional fuel requirements.

A The first development is characterized in that the fibers during or after extrusion into the green body of the filter body be introduced. This is the additional expense for the production the particle filter according to the invention low, so that it can be produced comparatively inexpensively.

At least some of the fibers may comprise a spun fiber yarn, whereby the contact between the ceramic matrix of the shell and the fibers is improved, which ultimately benefits the strength comes.

Around also be able to absorb radial and tangential stresses, At least some of the fibers may be a fabric or net form, so that at least some of the fibers at an angle are arranged to each other.

A Alignment of the fibers allowed in the axial direction of the shell a particularly effective absorption of the coat especially critical axial stresses. In addition, the embedding is in such a way Aligned fibers particularly easy in the extrusion process integrated. With axially aligned fibers so already achieved a significant improvement in the strength of the shell at the same time particularly simple production.

Possible But it is also that at least some of the fibers in the circumferential direction are arranged of the shell, which also radial and tangential Tension can be absorbed. Also an orientation the fibers in spiral form is conceivable. In that case, would the coat can be quasi "wrapped" with the fibers. This is again comparatively easy to produce.

Around the strength of the jacket with the aim of a significant improvement To increase the life without simultaneously other problem areas too Generate, it makes sense if the fibers at least at operating temperature have a thermal expansion that is smaller than that thermomechanically induced stretching of the jacket.

Of the Filter body is usually made of a ceramic material, for example cordierite. For the fibers comes as a material also a ceramic material in question, in particular Carbon, alumina and / or silica. These fibers have sufficient temperature resistance to the after incorporating the fibers into the filter body Sintering process unscathed to survive. Ultimately is it matters the coefficient of thermal expansion of the fibers to match that of the ceramic matrix.

Brief description of the drawings

following Embodiments of the present invention are disclosed With reference to the accompanying drawings explained in more detail. In the drawing show:

1 a schematic representation of an internal combustion engine and an exhaust particulate filter;

2 a schematic longitudinal section through a filter body of the exhaust particulate filter of 1 ;

3 a perspective view of a portion of a first embodiment of the filter body of 2 ;

4 a representation similar 3 a second embodiment;

5 a representation similar 3 a third embodiment;

6 a representation similar 3 a fourth embodiment; and

7 a representation similar 3 a fifth embodiment.

Embodiments of the invention

In 1 an internal combustion engine carries the reference numeral 10 , Their exhaust gases are via an exhaust pipe 12 an exhaust particulate filter 14 fed. With this can during operation of the internal combustion engine 10 Soot particles from the exhaust pipe 12 flowing exhaust gas are filtered out. This is particularly necessary in diesel internal combustion engines to comply with legal requirements.

The exhaust particulate filter 14 comprises an overall substantially cylindrical housing 16 , in which a likewise substantially cylindrical filter body 18 is arranged. This may be, for example, an extruded shaped body of a ceramic material, for example cordierite. In operation, the filter body 18 in the direction of the arrows 20 from the exhaust gas of the internal combustion engine 10 flows through. An inlet side of the filter body 18 is in 1 in total with 22 , an outlet page with a total of 24 designated.

The basic structure of the filter body 18 comes from 2 show: then run parallel to a longitudinal axis 26 of the filter body 18 in this a variety of inlet channels 28 and exhaust ducts 30 , For clarity, in 2 but only a few of the intake channels 28 and 30 exemplified with reference numerals. The inlet channels 28 are in the area of the outlet side 24 by means of a closing section 32 , also called "plug", closed. The outlet channels 30 in turn are in the area of the inlet side 22 each by a corresponding closing section 34 locked. The inlet channels 28 are in the area of the inlet side 22 , the outlet channels 30 in the area of the outlet side 24 open. The walls 36 between the inlet channels 28 and the outlet channels 30 are porous and have a comparatively high permeability for the exhaust gas. As a radially outer boundary wall, the filter body 18 a coat 38 on.

During operation, the exhaust gas occurs 20 first in the inlet channels 28 a, then enters through the walls 36 through, according to the arrows 40 in 2 , and then passes through the outlet channels 30 from the filter body 18 out. When passing the exhaust gas through the walls 36 become soot particles in the exhaust gas on the inside of the inlet channels 28 deposited.

To avoid getting through on the insides of the inlet channels 28 deposited soot particles the permeability of the walls 36 is obstructed in an inadmissible manner, the filter body 18 "regenerated" from time to time. This means that the deposited soot particles are burned as part of an exothermic oxidation reaction. This can be done, for example, by adjusting the temperature of the exhaust gas 20 passing through the filter body 18 is passed, by engine measures of the internal combustion engine 10 is increased. For example, an additional injection of fuel, the combustion of which causes the increase in the exhaust gas temperature. The deposited soot particles are thus periodically degraded by said exothermic oxidation reaction to gaseous reaction products, which then pass through the walls 36 through and over the outlet channels 30 and the outlet side 24 of the filter body 18 can escape from this.

To increase the strength of the jacket 38 are in these, like out 3 it can be seen fibers 42 embedded. The jacket includes insofar a ceramic matrix 44 , for example, cordierite, and in this matrix 44 inserted or laid on these fibers 42 , The fibers 42 may be made of carbon, alumina and / or silica. To keep the production simple, the fibers should be 42 during or after extrusion into the green body of the filter body 18 be introduced. Important in this case is that the fibers 42 are sufficiently stable in temperature to survive unscathed the subsequent sintering can. It is also important that the material of the fibers 42 at least at operating temperature, so for example in a regeneration, has a thermal expansion which is smaller than the thermomechanically induced strain of the material of the matrix 44 of the coat 38 ,

How out 3 As can be seen, the fibers can 42 in the axial direction of the jacket 38 , as parallel to the longitudinal axis 26 of the filter body 18 be arranged. But it is also possible that they, as out 4 shows, in the circumferential direction of the jacket 38 are arranged.

In yet another embodiment accordingly 5 form the fibers 42 a fabric or a net, with fibers 42a in the axial direction and fibers 42b in the circumferential direction of the jacket 38 ,

In the embodiment according to 6 are the fibers 42 spiral around the longitudinal axis 26 of the filter body 18 wound, so they are opposite the circumferential direction at an angle A.

According to the embodiment of 7 Finally, the fibers can 42a and 42b also for example at an angle of ± 45 ° to the longitudinal axis 26 be arranged.

In principle, furthermore, that any combination of the in the 3 - 7 illustrated orientations of the fibers 42 possible are; It is crucial that the orientation and the choice of fibers strength of the jacket 38 optimally to the strength of the rest of the filter body 18 can be adjusted.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 10130338 A1 [0002]

Claims (9)

Particle filter ( 14 ), in particular exhaust gas particulate filter for an internal combustion engine ( 10 ), with a honeycomb filter body ( 18 ) in which alternately and overall in its longitudinal direction ( 26 ) running inlet channels ( 28 ) and outlet channels ( 30 ) are present and a radially outer shell ( 38 ), characterized in that the jacket ( 38 ) Fibers ( 42 ). Particle filter ( 14 ) according to claim 1, characterized in that the fibers ( 42 ) during or after extrusion into the green body of the filter body ( 18 ) are introduced. Particle filter ( 14 ) according to one of claims 1 or 2, characterized in that at least some of the fibers ( 42 ) spun fiber yarn. Particle filter ( 14 ) according to one of the preceding claims, characterized in that at least some of the fibers ( 42 ) form a fabric or net. Particle filter ( 14 ) according to one of the preceding claims, characterized in that at least some of the fibers ( 42 ) in the axial direction ( 26 ) of the jacket ( 38 ) are arranged. Particle filter ( 14 ) according to one of the preceding claims, characterized in that at least some of the fibers ( 42 ) in the circumferential direction of the shell ( 38 ) are arranged. Particle filter ( 14 ) according to one of the preceding claims, characterized in that at least some of the fibers ( 42 ) are arranged spirally. Particle filter ( 14 ) according to one of the preceding claims, characterized in that the fibers ( 42 ) at least at the operating temperature have a thermal expansion which is smaller than the thermo-mechanically induced elongation of the shell ( 38 ). Particle filter ( 14 ) according to one of the preceding claims, characterized in that the filter body ( 18 ) of a ceramic material, for example cordierite, with fibers ( 42 ) is made of a ceramic material, in particular carbon, alumina and / or silicon oxide.