DE102006059419A1 - Diesel particle filter for use in diesel engine of vehicle, has two different heating mediums with different electrical characteristics and output per unit area, where one medium covers inlet-sided front surface of particle filter - Google Patents

Abstract

The diesel particle filter has two different heating mediums with different electrical characteristics and output per unit area. A heat output of the heating medium with higher output per unit area amounts to 300 percent of heat output of the heating medium with lower output per unit area. The heating mediums draw through the particle filter in direction of flow of exhaust gases (6) and/or have a diameter from 0.8 to 2 millimeter. The latter heating medium covers an inlet-sided front surface of the particle filter. Independent claims are also included for the following: (1) a method for regenerating a diesel particle filter (2) a computer program product for performing a method for regenerating a diesel particle filter (3) a method for reducing emissions of diesel driven engine with a diesel particle filter.

Description

The The present invention relates to a particulate filter and a method for cleaning exhaust gases and for regeneration of particulate filters.

As a contribution to CO ₂ reduction, the low-consumption diesel engine is indispensable as a vehicle drive today. However, its disadvantages are comparatively high compared to other car drives such as natural gas or gasoline engines nitric oxide and soot emissions, which can be met, apart from engine measures only by consuming exhaust aftertreatments. DeNO _x systems and particulate filter systems have been developed here in recent years, and when the new exhaust gas legislation level Euro 4 (since 01/05) comes into effect in part, the series comes into force.

The Advantages of modern diesel engines with turbocharging and direct injection are low fuel consumption and high torque in the lower Speed range. These benefits appreciated by the end customer led to a significant increase in recent years market share in Europe. In some countries, the 50% mark already exceeded. In 2005, a market share expected to average 50% in Europe.

In spite of all still available motor optimization potentials such as during charging, mixture preparation and control combustion, and in particular the optimization of the dynamic Operating mode is not allowed within the next years expect the diesel engine with regard to soot emission even approaching the level of the petrol engine despite rapid advances in injection technology as a prerequisite a homogeneous diesel operation.

at Combustion of diesel fuel occurs in addition to soot attached to these polycyclic aromatic hydrocarbons (so-called PAH) as well as sulfates, water and metal oxides from engine wear and oil additives. The known oxidation catalysts convert only the accumulated Hydrocarbons, d. H. so-called soluble fraction and thus contribute to a slight reduction in Particulate emissions (<30%) at. However, the conventional catalyst technology is not in the Able to complete the chemically very complex carbon particles to eliminate. The only reliable method currently for serious reduction of such particles is in the filtering by means of suitable filter elements and in the subsequent Regeneration. This is the stored soot particle residue by setting the required thermal conditions almost residue-free burned.

Various filter technologies have been developed for filtering soot particles and their admixtures. One distinguishes between the following typical types:
Honeycomb filters ("honeycomb / wall flow filter") are produced in the extrusion process from cordierite (commercial vehicle applications) or silicon carbide (SiC) in the passenger car sector. In these filters, the exhaust gas flow is diverted due to resulting pressure forces in the filter channels through the filter wall, the particulate matter are filtered out and to form an even more filtering soot.

Candle filter are made of ceramic fibers or metal mesh, which are wound into a filter candle. The fibers are mostly made of silica or alumina (known as mullite) and are specially designed to improve filtration. In the flow through the Filter candle, the particles are deposited between the fibers, which usually forms no soot. This Principle-related difference is also known in the literature as depth filtration denotes and leads to a different exhaust back pressure behavior with increasing particle or ash loading.

For Sintered metal filters become metallic fibers or powders exactly defined grits to filter plates on coarse wire mesh sintered together. The soot particles are flowing through the resulting filter plate only on the surface deposited. This offers the advantage of safe avoidance of Exhaust gas blockages by non-regenerated filter channels (so-called. Open filter structures).

For Foam filters are made of alumina with ceria or silicon carbide (SiC) Foam body manufactured by casting and fire produced by Exhaust gas flows through, with the soot particles be stored in the structure. The filter efficiency leaves control over the pore size; is but rarely more than 40-50%. There is also the risk of a particle blow-off with full substrate under rapid acceleration.

Independently the filter design must regenerate the filter, i. H. the stored Soot is removed continuously or mostly periodically.

One possibility for regeneration is to heat the exhaust gases to temperatures of about 450 to 630 ° C in order to burn the soot particles fast enough. Efficient combustion of a soot particle requires temperatures above 600 ° C, which are difficult and infrequent to achieve in diesel exhaust even at full load. The addition of fuel additives that act as lösli Catalysts allow Rußabbrand on the filter already at temperatures above 350 ° C. A disadvantage of many manufacturers of the relatively high ash rate seen in this method (about 2/3 are additive ash and 1/3 oil ash).

ever according to the operating condition of the engine, therefore, measures are required safe and so gentle around the corresponding temperatures. as possible to reach for the drive unit. So can at. Operating conditions with low mass flows (City traffic with lots of no-load and frequent stop-and-go trips) used electrical heating means or ignition aids advantageous become. However, these systems have the disadvantage that the Regeneration only up to about 70 kg of exhaust gas / h is possible because it is too strong at higher throughputs Cooling of the heating medium comes and thus the Regenration either does not start or stops prematurely. Also is the energetic Effort then barely acceptable.

in the Driving operation are exhaust gas mass flows of up to 600 kg / h so that this regeneration method fails here. Around even with frequent trips without idle (eg highway driving) one To enable regeneration, others become conventional Methods such as the injection of oxidizing agents, in particular the Post-injection of fuel and exothermic reactions in the oxic or the Non Thermal Plasma (NTP), in which the soot through the oxidation is regenerated with O-radicals used. It lies on hand, that these methods are either structurally elaborate are (carrying the oxidant and controlling the injection) or the fuel consumption due to a high thermal mass / inertia increase all exhaust-related components. The guiding principle would be just the immediate ignition of the soot layer on the filter element, as the lavish heating of others Assemblies is completely avoided.

The DE 102 41 898 A1 suggests for the regeneration of particulate filters with reduced rich operation to arrange a flow divider in front of the particulate filter. This should be able to divide the exhaust gas stream into at least two partial streams in order to be able to supply a partial flow to a regeneration agent for the particle filter. Since only a part of the filter is regenerated at a time, the amount of regeneration agent to be used should be lower than when the entire filter is completely regenerated. However, this solution is structurally complex and therefore expensive. In addition, it is prone to failure because of the moving parts in the exhaust, as the moving parts are dirty and can bind, which affects the functionality in continuous operation.

Of the It is an object of the present invention to provide a particle filter and to provide a method of exhaust gas purification which is independent From the operating condition of the engine a structurally simple and fuel-efficient Allow regeneration of the particulate filter.

According to the invention succeeds the solution of this task by a diesel particulate filter (DPF) with heating means containing at least two different heating means in terms of their structure and power consumption has.

Of the Diesel particulate filter according to the invention is characterized characterized in that it comprises at least two different heating means having.

These Heating media can differ in different properties differ, for example in their design, in their size, their materials and / or principles of action.

preferred Heating means pass through the particle filter at least partially Flow direction and preferably have a diameter of 0.2 to 5 mm, preferably from 0.5 to 3 mm and in particular of 0.8 to 2 mm.

preferred According to the invention diesel particulate filter (DPF) are characterized in that the heating means are at least in their electrical properties, such as the spec. Power consumption and / or Radiation power, distinguish.

Preferably, the various heating means are not only separated from each other to operate, but also have different power ranges. Here diesel particulate filters (DPF) according to the invention are preferred, which have at least two different heating means and / or materials, which differ in their area performance (W / cm ² ).

The power consumption of the heating elements can be, for example, 0.1 to 10 kW, preferred values being between 0.25 and 5 kW, more preferably between 0.5 and 2.5 kW and in particular between 0.75 and 1.5 kW. Preferred surface powers are between 0.1 and 50 W / cm ² , preferably between 1 and 40 W / cm ² , more preferably between 5 and 35 W / cm ² and in particular between 10 and 30 W / cm ² .

Here are diesel particulate filters (DPF) according to the invention preferred in which the heating power of the heating medium with higher Area performance at least 150%, preferably at least 200%, more preferably at least 250% and especially at least 300% of the heating capacity of the other heating medium with lower area output is.

Preferably, the more powerful heating Medium limited to a smaller space and housed as the lower-power. In particular, the area coverage of the end face of the particulate filter, ie the proportion of the area occupying or electrically covering a heating element on the inlet side, is of importance. Here, diesel particulate filters (DPF) according to the invention are preferred in which at least one heating medium, preferably the heating medium with lower area coverage, covers at least 60%, preferably at least 70% and in particular at least 80% of the inlet-side end face of the particulate filter.

The Let diesel particulate filter according to the invention independent of the exhaust gas mass flow and thus independent regenerate from the operating condition of the vehicle. To a loaded To regenerate filters are first the - preferably area and volume smaller - but Heated more powerful heating elements, causing in the The area covered by them quickly starts the regeneration and the soot is burned locally there. This results in the particle filter "free burned" areas that the exhaust gas with less flow resistance than before unregenerated areas. After the regeneration of these from the powerful Heating elements heated zones of the particulate filter happens so the Main part of the exhaust stream these better permeable areas. As a result, the exhaust gas mass flow through the previously not regenerated Areas so far reduced that even at higher engine load pass exhaust gas mass flows through these areas, at least comparable with the exhaust gas mass flows at idle are. This now opens up the possibility to date not regenerated remainder of the particulate filter with the help of the second Heating heating element and there also the regeneration too start. This regeneration process starts relatively easily and Also does not break off prematurely, since the amount of exhaust gas to a critical Hypothermia is usually insufficient.

In order to the entire particle filter can be independent of the operating state of the vehicle and without addition of oxidizing agents, additives u. a. and the associated additional consumption or cost regenerated become. This process is further supported by the fact that at higher engine load by the alternator required for heating electrical energy is usually more stable available can be made.

Another object of the present invention is a method for the regeneration of diesel particulate filters (DPF), in which the diesel particulate filter has at least two different heating means, of which only one during a time t ₀ to t _{1 and} only in the period t ₁ to t ₂ others are put into operation.

Depending on the loading of the particulate filter and some engine data on the CAN bus (speed, load, battery voltage), possibly even in conjunction with a "soot loading model", the regeneration of the filter starts at a predefined time t ₀ be a period t ₀ to t ₁ first, and only in area less available but more powerful heating element heated so that created in the wake areas of good gas permeability in the filter. Once the particulate filter is burned off in the heated from the powerful heating element fields (time t ₁ ), the more powerful heating element is switched off and the regeneration of the remaining filter is started by switching on the lower-power heating element.

Preferred methods according to the invention are characterized in that the time interval t ₀ to t ₁ l 2 to 60 seconds, preferably 5 to 50 seconds, more preferably 10 to 40 seconds and especially 15 to 30 seconds lasts.

As already stated in the particle filter according to the invention, methods according to the invention are also preferred in which a heating element whose heating power (area power in W / cm ₂ ) is at least 150%, preferably at least 200%, is particularly heated in the time interval t ₀ to t ₁ is at least 250% and in particular at least 300% of the heating power of the heating element, which is heated in the period t ₁ to t ₂ .

Also preferred in the process according to the invention are variants in which the heating element which is heated in the time period t ₀ to t ₁ is 1 to 30%, preferably 2 to 25%, particularly preferably 5 to 20% and in particular 10 to 18% of the inlet side Covering face of the particulate filter or achieved with its effect.

Further Objects of the present invention are a controller which is designed such that the inventive Method in the control unit is executable as well a computer program product for carrying out the invention Method in which the method steps in a in the computer program product stored program are integrated. Optionally these features in a more powerful engine control unit (ECU / EDC).

One Another object of the present invention is a method to reduce the emissions of diesel engines with particulate filters, in which the exhaust gas purification system of the engine according to the invention Particulate filter includes.

The Invention will be clarified below with reference to drawings. Showing:

1 a diesel particulate filter according to the invention and the flow through it with exhaust gases;

2 a section through the diesel particulate filter according to the invention along the flow direction of the exhaust gases.

In 1 is a diesel particulate filter (DPF) according to the invention with a filter body 1 shown an inlet side 2 as well as an outlet side 3 and along the flow direction 6 is flowed through by exhaust gas. In or on the filter body 1 There are powerful heating elements that operate in their operation to heavily heated zones of small area 5 on the inlet side 2 lead the filter. Optionally, the heating elements may either be mounted in the region of the inlet side or may extend wholly or partly over the entire length of the DPF. In addition, the filter has less powerful heating elements that can heat the rest of the filter, with a limit 4 the conventionally lower heated area on the inlet side 2 of the filter exists. The more powerful heating elements are located in the inlet area and ignite the soot in this area during regeneration. Once the soot is locally ignited, the soot combustion typically continues through the DPF, creating "free burned" areas 7 ( 2 ).

2 shows a section through the filter according to the invention, in which the preferably larger in terms of area and volume smaller powerful heating elements are heated, which starts in the heated areas so the regeneration and the soot is burned. As a result, in the particle filter "free burned" areas 7 produced, ie those regenerated areas with low flow resistance, which allow the exhaust gas better than the previously unregenerated areas 8th with high flow resistance. The main exhaust gas mass flow is at least partially diverted to the spent areas due to the resulting pressure gradient between spent and non-spent areas. As a result, the cooling effect caused by the mass flow, which is maximum in the DPF cross-sectional area center, is reduced, as a result of which reliable regeneration can be achieved there even with less power.

1

filter body

2

inlet side

3

outlet

4

border the conventionally weaker heated area on the inlet side

5

strongly heated zones of small area on the inlet side

6

Flow direction the exhaust gas

7

regenerated Areas with the lowest flow resistance

8th

so far unregenerated areas with high flow resistance

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10241898 A1 [0014]

Claims (13)

Diesel particle filter (DPF) with heating means, characterized in that it comprises at least two different heating means. Diesel particulate filter (DPF) according to claim 1, characterized characterized in that the heating means are at least in their electrical Distinguish properties. Diesel particle filter (DPF) according to one of claims 1 or 2, characterized in that it comprises at least two different heating means, which differ in their area performance (W / cm ² ). Diesel particulate filter (DPF) according to claim 3, characterized characterized in that the heating power of the heating medium with higher Area performance at least 150%, preferably at least 200%, more preferably at least 250% and especially at least 300% of the heating capacity of the heating medium with lower surface output is. Diesel particulate filter (DPF) according to one of the claims 1 to 4, characterized in that the heating means the particle filter at least partially in the flow direction and / or a diameter of 0.2 to 5 mm, preferably from 0.5 to 3 mm and in particular from 0.8 to 2 mm. Diesel particulate filter (DPF) according to one of the claims 1 to 5, characterized in that at least one heating means, preferably the heating medium with lower area performance, at least 60%, preferably at least 70% and in particular at least 80% of the inlet-side end face of the particulate filter covers. Process for the regeneration of diesel particulate filters (DPF), characterized in that the diesel particulate filter has at least two different heating means, of which only one is heated during a time t ₀ to t ₁ and only the other in a time t ₁ to t ₂ . A method according to claim 7, characterized in that the time interval t ₀ to t ₁ 2 to 60 seconds, preferably 5 to 50 seconds, more preferably 10 to 40 seconds and especially 15 to 30 seconds lasts. Method according to one of claims 7 or 8, characterized in that in the period t ₀ to t _1, a heating element is heated, the heating power (area power in W / cm ₂ ) at least 150%, preferably at least 200%, more preferably at least 250% and in particular at least 300% of the heating power of the heating element, which is heated in the period t ₁ to t ₂ . Method according to one of claims 7 to 9, characterized in that the heating element, which is heated in the period t ₀ to t ₁ , 1 to 30%, preferably 2 to 25%, particularly preferably 5 to 20% and in particular 10 to 18 % of the inlet side face of the particulate filter covers. Control unit designed such that the Method according to one or more of claims 7 to 10 executable in the control unit. Computer program product for executing the Method according to one or more of claims 7 to 10, characterized in that the method steps in a in program stored in the computer program product. Method for reducing diesel-driven emissions Engines with particulate filters, characterized in that the exhaust gas purification system of Motors a particulate filter according to one of claims 1 to 6 includes.