EP1304455B1 - Particulate filter for purifying exhaust gases of internal combustion engines - Google Patents

Abstract

A particle filter for cleaning motor vehicle exhaust gases has pot shaped inlet channels (9) with end bars into which particle-laden exhaust gases (3) flow and parallel adjacent outlet channels (10). An electric heater (15) in the base of the outlet channels burns off layers deposited in the pores (13) between the channels.

Description

The present invention relates to a particulate filter for cleaning engine exhaust gases, with cup-shaped inlet channels, which are provided at the end with an inlet channel bottom and in which particle-laden exhaust gases, as well as adjacent parallel to the inlet channels arranged and this cup-shaped aligned outlet channels, which each end with a Outlet channel bottom are provided and which derive the purified exhaust gases, which settles through the filtering of the porous, flow-through wall portions of the inlet channel, a particle layer which is burned to regenerate the particulate filter via electrical heating means.

Particulate filters of this type are usually used to reduce the particulate emissions in the exhaust gases of internal combustion engines - especially diesel engines. The technical effort to meet strict emission standards is significant with the current possibilities. For example, a more than 90% reduction in particulate emissions makes it essential to equip Diesel vehicles with particulate filters, for example, and also requires active measures to suffocate them. According to realistic estimates, additional fuel consumption of more than 5% is to be planned for this purpose, because the filter arrangement which is necessarily to be switched into the exhaust gas flow causes an increased energy requirement. The energy requirement increases with increasing sooting of the particulate filter, that is with increasing particle layer. However, the particle layer can be eliminated by burning in order to regenerate the particle filter in this respect.

A particle filter is out of the US 6,101,793 known. The existing of a porous ceramic particulate filter has elongated pot-shaped inlet channels, in which flow the particle-laden exhaust gases generated by the diesel engine. Exhaust passages are arranged in parallel adjacent to the inlet channels, which discharge the filter-cleaned exhaust gases to the atmosphere. The outlet channels are also cup-shaped, but aligned inversely to the inlet channels. In this arrangement, the filtering takes place when flowing through the porous common wall sections, forming a particle layer on the part of the inlet channel. The inlet channels and the outlet channels here have a square cross-section. The bottom portions of the pot-shaped channels are formed by various plugs which correspond to the channels close their orientation described above at one end.

For regeneration of the particulate filter, this further comprises electrical heating means, which are arranged on the filter output side in the region of the openings of the outlet channels. A fan which is switched on in the following exhaust pipe between the particle filter and the atmosphere cooperates with the electrical heating means for regeneration of the particle filter. The fan is turned on at standstill of the diesel engine for a defined period of time, so that an air flow flows backwards over the heated electric heating means, whereby the air flow heats, so that burning of the particle layer begins. However, this known solution for the regeneration of the particulate filter has the disadvantage that a relatively high technical complexity is required to produce the heated air stream.

Another particle filter is out of the US 5,782,941 known, here for regeneration another technical path is taken. The particle filter is constructed from an outer tubular filter part, in which an inner, smaller tubular filter part is coaxially inserted. This second filter part is closed on the side inflicted by the particle-laden exhaust gases and thus forms a cup-shaped outlet channel. The region formed between the second filter part and the first filter part is also to be regarded as a pot-shaped inlet channel. Herein a cylindrical tube-like shaped and provided with openings sieve-like heating means is arranged. The passing by Particle-laden exhaust gases transport in a regeneration of the particulate filter, the heat generated by the electric heating means to the particle layer on, which thereby burns off. Although the electrical heating means according to this prior art is integrated directly into the exhaust gas flow, so that no additional means for generating a heated air flow are required; However, the operation of the large-area cylinder-shaped heating means requires a fairly high energy consumption.

A generic particle filter is from the US 4 512 786 A known. Therein a cleaning device for purifying diesel exhaust gases is disclosed, which has a filter block for filtering exhaust particles in the exhaust system, wherein also a heating element for burning accumulated soot particles is provided. The heating means are arranged in the channels running parallel in the filter block.

From the US 4,872,889 A It is known to provide grooves in inlet channels of a filter element which carry the heating elements. For thermal insulation of the heating elements cover is provided. To stabilize the position of the heating elements additional recesses may be provided in the end cover. Disadvantage of the arrangement, however, is that the heating elements are mounted directly in the inlet of the exhaust gas. Since electrically conductive, graphitic carbon is a major component of the exhaust gas, a risk of short circuit with the adjacent heating wire is relatively high.

It is the object of the present invention to provide a particle filter for purifying exhaust gases of an internal combustion engine, which can be regenerated in a simple way, energy-saving and with high efficiency. Further, it is an object of the present invention to provide a particulate filter which allows separation between the heating medium carrier and the particulate filter body.

The object is achieved on the basis of a particle filter according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims give advantageous developments of the invention.

The invention includes the technical teaching of arranging the electrical heating means of a particulate filter in at least part of the outlet channels in the region of the outlet channel bottom in such a way that the thermal radiation emitted by the electrical heating means triggers burning off of the particle layer located in the adjoining inlet channels.

An advantage of the inventive arrangement of the electric heating means is that this does not disturb the flow of exhaust gas when it enters the particle filter. Since the electric heating means are located in a region of the outlet channels, which is not located in the region of the exhaust gas flow, the introduced electrical energy for heat generation is used much better. As a result, the heat given off by the electric heating means can be transferred to the adjacent filter walls mainly by heat radiation. The ignition temperature for the particle layer depends on the distribution of soot, in particular on the layer thickness and the packing density as well as the soot quality over the filter length. Since the heat generated by the electrical heating means is transported on with the exhaust gas flow, the particle-layer-affected wall sections thereby heat up, which supports the regeneration of the particle filter. The inventive arrangement of the electric heating means on the side of the purified exhaust gas also corrosion processes can be avoided as a result of soot and ash deposits sustainable. The inventively designed particulate filter allows self-supporting regeneration, even immediately after a cold engine start in idle mode. The electric heating means emit heat due to their high surface temperature, which is absorbed by the adjacent wall sections. This amount of heat starts the regeneration on the inlet side of the particulate filter. Part of the heat is released by turbulent flows in the outlet channels to the local wall sections, whereby a heating takes place. As a result, the heat generated by the electric heating means is better used for regeneration and prevents interruption of Rußabbrandes with a very high probability. The self-supporting oxidation of the particle layer then proceeds in the flow direction of the exhaust gas to the gas outlet side and thus restores the original exhaust backpressure of the particulate filter in the unloaded state, that is without a particle layer.

In order to reduce the total number of electric heating means required, according to a further measure improving the invention, they are adjacent to those having electrical means Each of the heating channels equipped outlet channels in each case unheated - that is equipped with no electrical heating means equipped outlet - on. In order to achieve complete regeneration of the particulate filter, it is not necessary for each exhaust passage to be equipped with an electrical heating means. With a square channel cross-section, the number of required electrical heating means can thus be reduced to 25% of the number of outlet channels.

Preferably, the electrical heating means are operated with a pulse width modulated supply voltage to save electrical energy. This pulse width modulated supply voltage needs to be maintained only over a short defined period of time, which starts the burning of the particle layer. After the start triggered by the electrical heating means, the further burning process continues automatically because of the exothermic reaction. By thus achieved minimization of electrical energy requirements, the electrical system of a diesel engine-powered vehicle is minimally burdened.

In order to ensure effective heat radiation of the electric heating means, these are preferably formed in the manner of a coiled kantal wire. The electrical heating means are advantageously at least partially connected in series with each other. Thus, a burn through of individual electrical heating means does not lead to the failure of the entire particulate filter. Individual groups of series-connected heating means enable a sector-by-sector heating of the particulate filter.

The electrical heating means are preferably arranged protruding from the associated outlet channel bottom in the outlet channel, and to the extent that an optimal blasting in the adjacent edge regions of the inlet channels can be achieved. The electric heating means need not protrude very far into the outlet channel, in order to fulfill their function according to the invention.

According to a further measure improving the invention, the particle filter is constructed in two parts. This consists of a disc-shaped outlet kanaiboden side particulate filter cover part, on the contact side to a particulate filter main part, the heating means are attached. On the one hand, the particle filter cover part thus fulfills the function of a support for the electrical heating means and on the other hand also serves to form the outlet channel bottoms.

Both parts of the particulate filter preferably consist of the same filter material and can be produced by separation. The outlet channel bottoms can be formed by plug elements introduced into the particulate filter cover part accordingly. The electrical heating means are preferably attached to the particulate filter cover part by gluing with a temperature-resistant adhesive. Alternatively, it is also conceivable to detachably insert the heating means into the outlet channel bottoms of the particle filter cover part, which ensures easier replacement in the event of repair. The attached to the contact side of the particulate filter cover part heating means are preferably in corresponding recesses, so that when mounted heating means a overall flat contact side to the particle filter main part out.

According to a further embodiment, the heating means can also be arranged projecting into outlet channel sections of the particle filter cover part in the direction of the inlet side and thus be placed entirely on the part of the correspondingly thicker particle filter cover part. For a better management of the heating means is achieved. Namely, the heating means need not necessarily be arranged in a certain direction along an exhaust passage. The length of the outlet duct sections of the particulate filter cover part should be slightly larger than the length of the heating elements themselves. A flow gap can also be maintained between the particulate filter cover part and the main part of the particulate filter, wherein the ducting in the particulate filter main part should be offset relative to the particulate filter cover part by correspondingly introduced plug elements, in order to provide favorable flow guidance to accomplish. Over the existing flow gap, the electrical wiring of the heating elements can be realized in an advantageous manner. In that regard, can be dispensed with a sealed joining of the two filter parts.

The inventively designed particulate filter can be used in accordance with a further measure improving the invention in the context of a filter assembly in which the particulate filter directly downstream of a nitrogen oxide Abscheidermodul. The nitrogen oxide separator module comes into direct contact with the gas outlet side of the particulate filter. The nitrogen oxide separator module is used for the Endstickung of the exhaust gas, wherein a desulfation can be advantageously carried out. These modular arrangement allows a significant saving in platinum-containing coating materials.

Due to the direct downstream connection of a nitrogen oxide separator module to a heated particle filter, the exothermic energy released in the course of the regeneration of the particle filter can also be used for the regeneration of the downstream nitrogen oxide separator, thereby significantly improving the efficiency of the entire filter arrangement. This simultaneous regeneration process of particulate filter and nitrogen oxide separator also significantly reduces the control engineering effort. The purified exhaust gases leaving the heated particulate filter have a temperature of up to 700 ° C. With the exhaust gas flow, this heat is transported on to the nitrogen oxide separator module where it initiates regeneration in the form of desulfation. Desulfation removes sulfate deposits in the nitrogen oxide separator module due to a relatively high sulfur content of the diesel fuel and sulfur-containing components of the oil.

The filter arrangement described above, a further particle filter can be followed, which in turn can be followed by another nitrogen oxide separator module. This further particulate filter is preferably unheated and provided with a catalytic coating. The multiple arrangement significantly increases the efficiency of filtering. The modular design of the filter assembly also offers significant energy advantages. Thus, the compact design, a heat integration to reduce energy consumption possible and at the same time the resulting during the regeneration of uncoated particulate filter gas components CO and HC are used directly for the regeneration of the subsequent nitrogen oxide Abscheidermoduls and thus degraded.

Fig. 1

eine schematische Darstellung einer aus Partikelfiltern und Stickoxid-Abscheidermodulen bestehende Filteranordnung,

Fig. 2

eine Prinzipdarstellung der Funktionsweise eines erfindungsgemäß ausgebildeten Partikelfilters,

Fig. 3

eine schematische Draufsicht auf die eingangsseitige Stirnfläche des Partikelfilters,

Fig. 4

eine schematische Seitenansicht eines geteilt aufgebauten Partikelfilters mit hieran angebrachten elektrischen Heizmitteln.

Fig. 5

eine schematische Seitenansicht eines geteilt aufgebauten Partikelfilters mit hieran angebrachten elektrischen Heizmitteln in einer anderen Ausführungsform.

Further measures improving the invention will be described in more detail below together with the description of a preferred embodiment of the invention with reference to FIGS. It shows:

Fig. 1

a schematic representation of a consisting of particulate filters and nitrogen oxide Abscheidermodulen filter assembly,

Fig. 2

a schematic representation of the operation of a particulate filter designed according to the invention,

Fig. 3

a schematic plan view of the input-side end face of the particulate filter,

Fig. 4

a schematic side view of a shared particulate filter with attached thereto electrical heating means.

Fig. 5

a schematic side view of a shared particulate filter with attached thereto electrical heating means in another embodiment.

One according to Fig. 1 constructed particulate filter assembly for purifying exhaust gases of a diesel engine comprises a partened in a housing heated particulate filter 2. On the input side into the particulate filter 2 enter particle-laden exhaust gases 3, which arise during operation of a - here not shown - diesel engine.

The particulate filter 2 is equipped with electric heating means 4 for regeneration, which will be described in more detail in the following place. The cleaned exhaust gases leaving the heated particle filter 2 are fed to an adjacent nitrogen oxide separator module 5. The nitrogen oxide separator module 5 is provided with a suitable catalyst material and serves to eliminate harmful nitrogen oxides contained in the exhaust gases. According to the illustrated embodiment, the nitrogen oxide separator module 5 is followed by a further particle filter 6, which is here, however, unheated. The regeneration of this unheated particulate filter 6 is taken over the heating means 4 of the front particulate filter 2 by the heat from the particle oxidation in the particulate filter 2 with. The heat required for this purpose is forwarded accordingly via the exhaust gas flow. The unheated particle filter 6 is provided with a catalytic coating. According to the modular structure shown here, the unheated particle filter 6 is finally followed by a further nitrogen oxide separator module 7. The exhaust gases 8 purified via this alternating filter arrangement reach the atmosphere after leaving the housing 1.

According to Fig. 2 the heatable particle filter 2 consists of pot-shaped inlet channels 9, as well as parallel adjacent to the inlet channels 9 arranged outlet channels 10. To form the cup shape, the inlet channels 9 are provided at the end with an inlet channel bottom 11; the outlet channels 10 are closed on the input side with an outlet channel bottom 12. Due to their orientation, the particle-laden exhaust gases 3 flow into the inlet channels 9 for filtering. These flow through the porous wall sections 13, which are formed by the adjacent arrangement of the inlet channels 9 to the outlet channels 10, and pass through the outlet channels 10 as purified exhaust gases 8 to the atmosphere. As a result of the filtering of the particle-laden exhaust gases 3 through the porous wall sections 13, a particle layer 14 is deposited on the wall sections 13 on the part of the inlet channel 9.

For the regeneration of the particulate filter 2 electrical heating means 15a, 15b are provided, which are arranged in the outlet channels 10 in the region of the outlet channel bottom 12.

To save electrical energy, the electric heating means 15a, 15b are operated with a pulse width modulated supply voltage, which is generated by a generator unit 16, starting from the voltage source 17. The electric heating means 15 are designed in the manner of a coiled kangal wire and are arranged projecting from the associated outlet channel bottom 12 into the outlet channel 10.

The heat radiation emitted by the electrical heating means 15 penetrates the wall sections 13 in the region of the associated outlet channel bottoms 12, heats the coating to the activation temperature and thus triggers the burning off of the particle layer 14 located in the adjacent inlet channels 9.

By the exhaust gases flowing through the particle filter 2, the heat is transported along the particle layer 14 in the direction of the inlet channel bottoms 11 for burning off the entire particle layer 14, wherein the burning takes place automatically after the start (exothermic reaction).

According to Fig. 3 adjacent to the equipped with electric heating means 15 outlet channels 10a each unheated outlet channels 10b. The unheated exhaust ducts 10b are not provided with an electric heating means 15 with respect to the heated exhaust ducts 10a. As shown here, the outlet channels 10 and the inlet channels 9 have a square cross section, so that in the illustrated arrangement of the electric heating means 15 only 25% of the outlet channels 10 are to be provided with an electric heating means 15 to allow complete regeneration of the particulate filter 2 ,

With reference to Fig. 4 2, the particle filter 2 is constructed in two parts and consists of an inlet-side disk-shaped particle filter cover part 18, which has a contact side 20 which comes into contact with a particle filter main part 19. The particulate filter cover 17 mainly serves the attachment or Receiving the heating means 15. The heating means 15 are connected in this embodiment by gluing with a temperature-resistant adhesive to the particulate filter cover member 18. In order to form a flat contact side 20 to the particulate filter main part 19 in the fastened state of the heating means 15, the heating means 15 are inserted within corresponding recesses on the contact side 20 of the particulate filter cover part 18. After joining the particle filter cover part 18 with the particle filter main part 19, the heatable particle filter 2 according to the invention is formed.

According to the embodiment according to Fig. 5 For example, the heating means 15a are arranged in the individual outlet channel sections 10a of the particulate filter cover part 18a, projecting in the direction of the inlet side, and thus placed entirely on the side of the correspondingly thicker particulate filter cover part 18a. The length of the outlet channel sections 10a of the particulate filter cover part 18a is slightly larger than the length of the heating elements 15a. In addition, there is a flow gap 22 between the particle filter cover part 18a and the particle filter main part 19a, wherein the channel guide in the particle filter main part 19a is displaced relative to the particle filter cover part 18a by correspondingly inserted plug elements 21a in order to provide a favorable flow guidance. Via the existing flow gap 22, the electrical wiring of the heating elements 15a takes place.

LIST OF REFERENCE NUMBERS

1

casing

2

Particle filter, heated

3

Exhaust gases, particle laden

4

heating

5

Nitrogen oxide separator module

6

Particle filter, unheated

7

Nitrogen oxide separator module

8th

Exhaust gases, cleaned

9

inlet channel

10

exhaust port

11

Inlet channel bottom

12

Auslasskanalboden

13

wall section

14

particle layer

15

heating

16

generator unit

17

voltage source

18

Particulate filter cover part

19

Particulate filter main part

20

Contact

21

plug member

22

flow gap

Claims (12)

1. A particulate filter for purifying combustion engine exhaust gases, comprising pot-shaped intake ports (9) which are provided on the end side with an intake port floor (11) and in which particulate-loaded exhaust gases (3) flow in, and exhaust ports (10) which are arranged parallel adjacent to the intake ports (9), are provided on the end side with an exhaust port floor (12) and discharge the purified exhaust gases (8), with a particulate layer (14) being deposited as a result of the filtering on the interposed porous wall sections (13) on the side of the intake port (9) which are flowed through, which layer can be incinerated for regeneration via electric heating means (15), and the electric heating means (15) being arranged in at least a part of the exhaust ports (10) in such a way on the side of the purified exhaust gas in the region of the exhaust port floor (12) that the thermal radiation emitted by the electric heating means (15) triggers the incineration of the particulate layer (14) disposed in the adjacent intake ports (9),
   characterized in that
   the particulate filter is arranged in two parts, with the particulate filter consisting of a particulate-filter main part (19) and a disk-like particulate-filter cover part (18) on the side of the exhaust port floor, with the electric heating means (15) being fastened on the contact side (20) of the particulate-filter cover part (18) to the particulate-filter main part (19), and the particulate-filter cover part (1) being used for forming the exhaust port floor (12).
2. A particulate filter according to claim 1, characterized in that unheated exhaust ports (10b) are each adjacent to the exhaust ports (10a) provided with electric heating means (15) in order to reduce the total number of electric heating means (15).
3. A particulate filter according to claim 1, characterized in that for saving electric power the heating means (15) are operated with a pulse-width modulated supply voltage which is provided for triggering the incineration of the particulate layer (14) during a defined period of time.
4. A particulate filter according to claim 1, characterized in that the heating means (15) are arranged in the manner of a coiled Kantal wire.
5. A particulate filter according to claim 1, characterized in that the individual heating means (15) which are associated with the exhaust port floors (12) are connected at least partly in series with one another.
6. A particulate filter according to claim 1, characterized in that originating from the associated exhaust port floor (12) the heating means (15) are arranged to protrude into the exhaust port (10).
7. A particulate filter according to claim 1, characterized in that the heating means (15) are connected in a non-detachable manner with the particulate-filter cover part (18) by gluing with a temperature-resistant adhesive.
8. A particulate filter according to claim 1, characterized in that the heating means (15) are detachably inserted into the exhaust port floors (11) of the particulate-filter cover part (18).
9. A particulate filter according to claim 1, characterized in that plug elements (21) are provided which seal the exhaust ports (10) for forming the exhaust port floors (11).
10. A particulate filter according to claim 1, characterized in that the heating means (15c) are arranged in exhaust port sections (10a) of the particulate-filter cover part (18a) to protrude in the direction of the intake side, with the length of the exhaust port sections (10a) of the particulate-filter cover part (18a) corresponding at least to the length of the heating elements (15c).
11. A particulate filter according to claim 10, characterized in that a flow gap (22) exists between the particulate-filter cover part (18a) and the particulate-filter main part (19a), with the guidance of the port in the particulate-filter main part (19a) occurring in an offset manner in relation to the particulate-filter cover part (18a).
12. A particulate filter according to claim 11, characterized in that the offset guidance of the port between the particulate-filter main part (19a) and the particulate-filter cover part (18a) occurs through plug elements (21a) introduced accordingly in the face surface of the particulate-filter main part (19a).

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