DE102006059966A1 - particulate Filter - Google Patents

Abstract

Particulate filter (1) for cleaning exhaust gases of an internal combustion engine, with a substrate (3) traversed by flow channels (2) and at least partially comprising a catalytic coating and comprising an inflow region (4) and an outflow region (5), wherein the particulate filter (1) comprises a first flow section (6) which faces towards the inflow region (4) and which is connected to an electric heating means (7), and a second flow section (8) which faces away from the inflow region (4) and which is designed without heating means.

Description

The The invention relates to a particulate filter for purifying exhaust gases an internal combustion engine from a traversed with flow channels carrier, the an inflow area and an outflow area having.

For the reduction the pollutant emissions and in particular the particulate emissions From diesel engines, the use of particulate filters is known. As during the running operation of a diesel engine a more or less large number of particles in the filter settles, is a regeneration of the particulate filter required to function such a particulate filter and the appropriately equipped diesel engine over a longer period to ensure. The real difficulty is not in the filtration the soot particles, but in the regeneration of the filters used. Carbon soot burns spontaneously only at temperatures of about 650 ° C. These temperatures will be but z. B. of modern diesel engines generally only at full load and too rarely achieved there. Therefore, additional, supporting measures necessary for the oxidation of the separated from the exhaust soot particles. In particular, during cold start such measures are necessary because the entire Exhaust system and the exhaust one for the regeneration necessary temperature does not yet have.

A distinction is made between active and passive regeneration measures: In the active measures, the temperature of the exhaust gas is raised, for example, by using an electrical heating means via the temperature threshold necessary for the oxidation of the soot. The US 5,259,190 describes a particle filter that can be regenerated by electrical heating. In the case of regeneration, uniform heating of the entire cross-sectional area of the particle filter is achieved with this filter so that all the filter cells are regenerated at the same time. Such measures are always associated with an increased load on the electrical system and thus with a fuel consumption.

at the passively attacking systems is z. B. by use of organometallic fuel additives, the soot ignition temperature lowered. A disadvantage of this passive regeneration process is that the additive after regeneration of the particulate filter in the form of an ash, z. As cerium ash, accumulates in the filter. in addition An ash comes from the combustion of the discharged with the exhaust gas lubricating oil (Oil ash). The cereal ash, the approximately can make up two-thirds of the total, together with the oil ash a powdered, flaky composition remaining as residue after combustion of soot remains in the filter. After a certain period of operation of the internal combustion engine can depending on size and oil consumption of the engine accumulate several hundred grams of ash in the filter and significantly increase the exhaust back pressure, which with a continuous increasing fuel consumption is connected. Therefore, such Systems not for the entire life of a vehicle can be designed.

Of the Invention has for its object to provide a particle filter, which avoids the disadvantages mentioned in the regeneration, in particular represents a simple and compact unit, with at the same time high production and production costs are avoided. Furthermore If a particulate filter should be created, in particular at a cold start of the motor vehicle a satisfactory regeneration of the particulate filter allows.

The The object is achieved by a particle filter having the features of the claim 1 solved. In the dependent claims the advantageous developments of the particulate filter according to the invention are described.

According to the invention, the particle filter has a first flow section facing the inflow region, which is connected to an electrical heating means. Furthermore, the particle filter comprises a second flow section which faces away from the inflow region and is equipped with no heating agent. The particulate filter according to the invention makes it possible to achieve a satisfactory regeneration of the particulate filter, in particular during a cold start of the motor vehicle, in which the exhaust gases of the internal combustion engine have a low temperature (depending on the outside temperature, 100 ° C-150 ° C). As the exhaust gas passes through the inflow region into the first flow section of the particulate filter, the catalytic coating of the carrier in the first flow section causes a catalytic reaction. Preferably, the catalytic coating comprises precious metals such as platinum and / or palladium and / or rhodium. Platinum and palladium can significantly accelerate the oxidation of hydrocarbons and carbon monoxide, with rhodium favoring the reduction of nitrogen oxides. The catalytic coating forms a highly charged (sharp) oxidation catalyst, which adsorptively splits (dissociates) the oxygen atoms contained in the exhaust gas at noble metal centers. By a timely and rapid activation of the electric heating means, the first flow section is brought to a temperature at which it comes to a self-ignition of the (filtered) particles contained in the first flow section. It has shown that at a temperature of the first flow section of about 500 ° C-650 ° C auto-ignition of soot particles is always possible. During this process, the soluble organic components (SOF) always attached to the soot particles play an important role. The heating process removes relatively high-boiling components (in some cases also fuel residues) from the soot particles (desorption). As a result, highly flammable vapors form in the immediate vicinity of the coating and the oxygen atoms adsorbed thereon. These ignite directly on the already (thermally) activated catalyst coating, which locally results in a subsequent particle burn-off in the first flow section.

During the Burn-up of soot in the first flow section becomes reaction heat (Exothermie) free, which flows through the exhaust gas flowing through the particulate filter is recorded. The exhaust gas flowing into the second inflow area is due to the heat gained enough heated up, that there is a Rußabbrand also in the second inflow area of the particulate filter comes, but without this second inflow by an electric heating means to a certain temperature to bring or hold. According to the present Invention is sufficient only an initial ignition in the first flow section of the particulate filter, to further burn the whole Particulate filter collected carbon soot arise with oxygen allow. Since only the first inflow region of the particulate filter be brought to a certain temperature by the heater a significant amount of electrical energy can be saved become.

at a preferred embodiment The invention features the carrier of the first flow section a particularly thermally conductive material on, which is preferably a light metal, for example magnesium, Calcium etc. can be. In one embodiment of the invention the thermally conductive material for example, be evaporated, z. B. by a vapor deposition (CVD / PVD process). In a further alternative embodiment, the thermally conductive material by an impregnation process on the carrier the first flow section applied become. By a repeated immersion in a metal salt-containing solution and by repeated drying, a reliable impregnation of the heat-conducting enabled Materials are achieved. Likewise, all electrochemical Coating process can be applied. Other alternative methods are natural conceivable. Due to the good thermal conductivity of the first inflow area can a rapid heating of this particulate filter component by the electric heating means to a desired temperature at which it to a self-ignition the soot particle comes, done.

In An alternative of the invention may be the first and the second flow section be two separate components. Preferably, the first and the second inflow area in a common housing arranged. The attachment of the two inflow areas on the housing, for example by a form-fitting and / or non-positive and / or cohesive Connection done. Conveniently, The first and second flow sections are spaced apart to each other, which serves in particular as an insulation gap. This Isolation gap runs substantially perpendicular to the exhaust gas flow. One of the advantages of such Isolation gap is that a satisfactory heating of the first flow section Can be done in a short time without a substantial amount of heat from the carrier of the first inflow area directly on the carrier of the second inflow area get lost.

at another alternative the first and second flow sections be integrally connected.

Of the carrier may in a preferred embodiment made of ceramic. However, it is also possible to choose the carrier Metal. The main advantage of a ceramic carrier is that the precious metal coating recover much easier leaves, as with a metal carrier. Furthermore, a ceramic carrier cost-effective produce and easier to coat. The metal carrier of for example, consist of a wound, corrugated metal sheet can, is advantageously formed very thin and thus has in relation to the ceramic carrier a lower mass and any variety of shapes. Furthermore wears the metal support to a better thermal conductivity and consequently to a homogeneous temperature distribution in the first and in the second flow area at.

In a further embodiment According to the invention, the first flow section has a volume up to a maximum of 40 the volume of the sum of the first and second flow sections is. It may well be sufficient that the first flow section only 10-20 of the total volume to a satisfactory regeneration of the particulate filter. However, this depends on different boundary conditions from, for example, the internal combustion engine used, the geometry of the particulate filter or of the noble metals used in the first Flow section.

Conveniently, an evaporator unit - especially for diesel fuel - be arranged in front of the particulate filter. The upstream evaporator unit, for example, enter unburned hydrocarbons (HC) in gaseous form, which are transported by the exhaust gas flow in the particulate filter. By these registered hydrocarbons, which are extremely flammable in the vaporized state, the soot particle ignition is supported in the first flow section. An activation of the evaporator unit is useful, for example, when the soot contained in the first flow section of the particulate filter is too dry (graphitized) and thus difficult to ignite. Activation of the evaporator unit may be operating point dependent and as needed.

Further Advantages, features and details of the invention will become apparent the following description, with reference to the drawing an embodiment the invention is described in detail. The can in the claims and features mentioned in the description each individually for itself or in any combination essential to the invention. It shows:

1 a particle filter according to the invention with a first or a second flow section.

1 shows a particle filter according to the invention 1 in a purely schematic representation. The particle filter has one with flow channels 2 crossed carrier 3 on, the one inflow area 4 and an outflow area 5 having. Furthermore, the particle filter includes 1 one the inflow area 4 facing first flow section 6 that with an electric heating medium 7 connected is. The particulate filter also has an inflow region 4 remote second flow section 8th on, which is designed without heating. In this embodiment of the invention, the first flow section 6 only provided with a catalytic coating. In the case of the catalytic coating, these are precious metals, for example platinum and / or palladium and / or rhodium.

The flow channels 2 of the particulate filter 1 are listed in the following embodiment square. Of course, the cross section of the flow channel 2 be pentagonal, hexagonal or polygonal. Alternatively, there is also a circular cross-section of the flow channels 2 possible.

As 1 clarified, are the first 6 and the second inflow area 8th as each formed a component. The first flow section 6 is to the second flow section 8th through a gap 9 spaced. This gap 9 (Distance between the first flow section 6 and the second flow section 8th ) is usually less than 1 mm.

The carrier 3 of the first flow section 6 is provided with a thermally conductive layer. Here, the thermally conductive layer is a light metal of magnesium. The use of alternative light metals is of course conceivable, for example, on the carrier 3 can be evaporated. In front of the particle filter 1 is a purely schematically illustrated evaporator unit 10 arranged, which adds a certain length of unburned hydrocarbons (HC) in gaseous form to the exhaust gas as needed. As 1 clarifies, the first flow section 6 a volume less than 30% of the volume of the sum of the first 6 and the second flow section 8th is.

The present particle filter 1 is characterized by good regeneration properties, in particular during a cold start of the internal combustion engine, not shown. Here, the still relatively cold exhaust gas flows at a temperature of about 100 ° C through the inflow region 4 of the particulate filter 1 and enters the first flow section 6 , Due to the catalytic coating of the first flow section 6 There is an oxygen splitting that ignites the ignition in the first flow section 6 Soot particles located under an activation of the electric heater 10 favored. The electric heater 10 heats the first flow section 6 to a temperature of about 600 ° C.

The thermally conductive material of the carrier 3 of the first flow section 6 favors a homogeneous heat distribution. In order to minimize the loss of heat, the gap is used 9 as an insulator. This prevents heat from passing through the support of the first flow section 6 over the gap 9 in the carrier 3 of the second flow section 8th arrives. Through the heated first flow section 6 arises a self-ignition of the particles, which is released by the particle burn heat, through the exhaust gas flow in the direction of the outflow area 5 is transported. The heated exhaust gas then passes through the gap 9 cut in the second Strömungsab 8th and triggers there also a Russabbrand. It is particularly advantageous that only a certain activation energy from the outside by the heating means 10 the particle filter 1 or the first flow section 6 must be supplied, thus an independent Partikelabbrandprozess throughout the particulate filter 1 expires. When heating 10 For example, it can be an induction heater, a heating wire heater or a half Head heating act.

If the soot particles are inside the particulate filter 1 too dry, it is advisable to use the evaporator 10 unburned hydrocarbons (HC) in gaseous form into the exhaust stream, whereby the ignition of the soot in the first flow section 6 is relieved.

1

particulate Filter

2

flow channels

3

carrier

4

inflow

5

Ausströmungsbereich

6

first flow section

7

electrical heating

8th

second flow section

9

Distance, Gap, insulation gap

10

evaporator unit

Claims (11)

Particle filter ( 1 ) for cleaning exhaust gases of an internal combustion engine with a flow channels ( 2 ), a catalytic coating at least partially having carrier ( 3 ), which has an inflow region ( 4 ) and an outflow area ( 5 ), characterized in that the particulate filter ( 1 ) one the inflow area ( 4 ) facing first flow section ( 6 ) provided with an electrical heating means ( 7 ) and the inflow region ( 4 ) facing away from the second flow section ( 8th ), which is designed without heating. Particle filter ( 1 ) according to claim 1, characterized in that the carrier ( 3 ) of the first flow section ( 6 ) has thermally conductive material. Particle filter ( 1 ) according to claim 2, characterized in that the thermally conductive material is a light metal. Particle filter ( 1 ) according to any one of the preceding claims, characterized in that the first ( 6 ) and the second flow section ( 8th ) are integrally connected. Particle filter ( 1 ) according to claims 1 to 3, characterized in that the first ( 6 ) and the second flow section ( 8th ) a distance ( 9 ) to each other. Particle filter ( 1 ) according to any one of the preceding claims, characterized in that the flow channels ( 2 ) have a square, a pentagonal, a hexagonal, a polygonal or a circular cross-section. Particle filter ( 1 ) according to one of the preceding claims, characterized in that the carrier ( 3 ) consists of a ceramic or metal. Particle filter ( 1 ) according to one of the preceding claims, characterized in that the first flow section ( 6 ) has a volume which is at most 40 in relation to the volume of the sum of the first ( 6 ) and the second flow section ( 8th ) is. Particle filter ( 1 ) according to one of the preceding claims, characterized in that an evaporator unit ( 10 ) in front of the particle filter ( 1 ) is arranged. Particle filter ( 1 ) according to any one of the preceding claims, characterized in that the catalytic coating comprises precious metals. Motor vehicle with a particle filter ( 1 ) according to one of the claims.