PARTICLE FILTER FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A particle filter for an internal combustion engine has a filter body (2) with a first channel (5) having a first end (7) facing a filter inlet (3) and a second end (8) facing a filter outlet (4), and a flow-through second channel (6) having a third end (9) facing the filter inlet (3) and a fourth end (10) formed facing the filter outlet (4). The second and third ends (8, 9) cannot accommodate flow therethrough. The channels (5, 6) are divided into a flow-through section (13) and a non-flow-through section (14). A wall (11) between the channels (5, 6) enables soot particles to be separated from exhaust gas flowing through the filter body (2) from the first channel (5) into the second channel (6). The non-flow-through channel section (14) has a heating element (15) to increase a reaction temperature in the filter (1) for burning off the soot particles.

Claims

1. A particle filter for an internal combustion engine, having a filter body (2), wherein the filter body (2) has a filter inlet (3) passable by a flow, and a filter outlet (4) passable by a flow, and wherein the filter body (2) has at least one first duct (5) passable by a flow, having a first end (7) that is configured so as to face the filter inlet (3), and a second end (8) that is configured so as to face the filter outlet (4), and a second duct (6) passable by a flow, having a third end (9) that is configured so as to face the filter inlet (3), and a fourth end (10) that is configured so as to face the filter outlet (4), and wherein the second end (8) and the third end (9) are configured so as to be impassable by a flow, wherein the ducts (5, 6) are capable of being divided into a duct portion (13) passable by a flow, and a duct portion (14) impassable by a flow, and wherein a flow transfer of an exhaust gas flowing through the filter body (2) proceeding from the first duct (5) to the second duct (6) is performed by way of a common duct wall (11) that is configured between the first duct (5) and the second duct (6), and wherein the duct wall (11) is configured so as to be capable of separating soot particles of the exhaust gas, and wherein: the first duct (5) and/or the second duct (6) for increasing a reaction temperature present in the particle filter (1) for burning off the soot particles have/has a heating element (15), wherein the heating element (15) is disposed in that duct portion (14) of the duct (5; 6) that is impassable by a flow and is configured from a functional material which reacts in an exothermicic manner when storing oxygen.

2. The particle filter of claim 1, wherein the heating element (15) for the release of heat is excitable with the aid of a modification of a combustion air ratio () of the exhaust gas.

3. The particle filter of claim 2, wherein: the heating element (15) for the release of heat is excitable with the aid of a modification of a combustion air ratio () of the exhaust gas from a combustion air ratio () having a value below 1 to a value above 1.

4. The particle filter of claim 1, wherein the heating element (15) has an element cross section (QE) which corresponds to a cross section (Q) of the duct (5, 6).

5. The particle filter of claim 1, wherein the heating element (15) is configured at least from cerium and zirconium oxides and/or the mixed oxides thereof.

6. The particle filter of claim 1 wherein the heating element (15) comprises palladium and/or rhodium.

7. The particle filter of claim 1, wherein the heating element (15) of the first duct (5) is configured from a first material, and the heating element (15) of the second duct (6) is configured from a second material that is dissimilar to the first material.

8. The particle filter of claim 7, wherein the first material is configured for reacting at low and medium temperatures present in the particle filter (1), and the second material is configured for reacting above all temperatures present in the particle filter (1).

9. The particle filter of claim 1, wherein a further heating element (15) is disposed in the duct portion passable by a flow.

10. The particle filter of claim 1, wherein the duct portion impassable by a flow has a stopper (12), wherein the heating element (15) is configured so as to completely or partially replace the stopper (12).

Description

BRIEF DESCRIPTION OF THE DRAWING

[0027] FIG. 1 in a t- diagram shows a profile of the combustion air ratio of exhaust gas, and in a corresponding t-T diagram temperatures in a particle filter according to the prior art, and in a particle filter according to the invention temperature profiles at various positions of the particle filter, determined with the aid of a simulated calculation.

[0028] FIG. 2 in a x-T diagram shows temperature profiles at various points in time in the particle filter according to the prior art and the particle filter according to the invention.

[0029] FIG. 3 in a schematic illustration shows a particle filter according to the invention

[0030] FIG. 4 shows an Ellingham diagram of the elements palladium and rhodium and the oxides thereof.

DETAILED DESCRIPTION

[0031] An abrupt temperature increase in a particle filter 1 according to the invention is capable of being initiated by way of an exothermic reaction of a material which has a high oxygen storage proportion in the event of an operation of an internal combustion engine (not illustrated in more detail) being converted from a load operation to an overrun operation. An air/fuel mixture supplied to the internal combustion engine herein is modified in terms of the proportions of said air/fuel mixture. The changeover is preferable so as to proceed from a so-called rich operation, which has a combustion air ratio of the air/fuel mixture having a value below 1, to a lean operation, which has a combustion air ratio of the air/fuel mixture having a value above 1. On account thereof, the exhaust gas of the internal combustion engine which flows through the particle filter 1 has an increased proportion of oxygen which triggers the exothermic reaction. A simultaneous overrun cut-off substantially increases the proportion of oxygen, on account of which a substantial increase in the temperature in the particle filter 1 is likewise achievable.

[0032] FIG. 1 in the lower portion in a t- diagram shows a profile L1 of a combustion air ratio over the time t ahead of a known particle filter. An abrupt change in the combustion air ratio from a value of presently approx. 0.95 to a value of significantly above 1 identifies a point in time of the operational changeover of the internal combustion engine from the load operation to the overrun operation by way of a fuel cut-off.

[0033] In the upper and the central portion of FIG. 1 temperature profiles T1, T2, and T3, calculated so as to depend on the operational changeover, are illustrated for various positions along a flow axis of the particle filter. The temperature profiles of a particle filter 1 according to the prior art are illustrated in the upper portion, and temperature profiles of a particle filter 1 according to the invention are illustrated in the central portion of FIG. 1. The temperature profile T0 corresponds to a so-called inlet temperature, thus to the gas temperature ahead of OPF.

[0034] The particle filter 1 according to the invention, which is schematically configured according to FIG. 3, has duct portions 13 passable by a flow, and duct portions 14 impassable by a flow. The temperature profiles T1 and T3 show a thermal behavior of the particle filter 1 in a plane close to a filter inlet 3, or close to a filter outlet 4, respectively, of the particle filter 1, thus in planes which also intersect duct portions 14 impassable by a flow. The temperature profile T2 shows the thermal behavior of the particle filter 1 close to a central plane of the particle filter 1, said central plane being configured so as to be centric between the planes of the filter inlet 3 and the filter outlet 4.

[0035] By virtue of the thermal capacity of the particle filter 1 per se, the temperatures T1, T2, T3 in the particle filter 1 according to the prior art follow the cooling inlet temperature T0 in a delayed manner. The temperatures T1, T2, T3 in the particle filter 1 according to the invention show other profiles. The temperatures T1, T3 of the planes having duct portions 14 impassable by a flow, immediately upon changing from the (slightly) rich to the lean mixture, increase vehemently in an only unnoticeably delayed manner, in this example by approx. 75 C. As soon as an exothermic filling of an oxygen reservoir in the duct portions 14 impassable by a flow has been completed, these temperatures T1, T3 also follow the steadily chilling inlet temperature T0 in a delayed manner.

[0036] The calculations were performed without taking into account a soot burn-off. Measurements (not illustrated in more detail) show that the soot burn-off progresses only very slowly with the particle filter 1 being at approx. 700 C. A regeneration of deposited soot is clearly identifiable at approx. 850 C. The particle filter 1 without soot has hardly regenerated for the load case illustrated here. However, the particle filter 1 according to the invention, having the duct portions 14 impassable by a flow, ignites the soot burn-off such that the latter then progresses in a self-accelerating, or self-preserving manner up to the regeneration being largely completed.

[0037] FIG. 2 in an x-T diagram shows temperature profiles at various points in time t0, t1, t2, t3, t4 before and after a change over from a (slightly) rich load operation of the internal combustion engine to the overrun operation by way of the fuel cut-off in the direction of the flow axis of the particle filter 1. The temperature profiles t0, t1, t2, t3, t4 in the particle filter 1 according to the prior art are illustrated in the upper portion of FIG. 2, and the temperature profiles t0, t1, t2, t3, t4 in the particle filter 1 according to the invention are illustrated in the lower portion of FIG. 2.

[0038] The temperature profile t0 corresponds to a profile before the operational changeover. The temperature profiles t1, t2, t3, t4 are temperature profiles after the operational changeover, wherein the temperature profile t1 20.2 sec., the temperature profile t2 21.2 sec., the temperature profile t3 22.2 sec, and the temperature profile t4 23.2 sec correspond to a temperature profile across the flow axis after the operational changeover.

[0039] The particle filter 1 according to the invention for the internal combustion engine (not illustrated in more detail) is configured in a schematic illustration according to FIG. 3. In the operation of the internal combustion engine which is embodied in the form of a direct-injection gasoline engine, exhaust gas that contains soot particles is created by virtue of a combustion of the air/fuel mixture.

[0040] The particle filter 1 has a filter body 2 having a filter inlet 3 passable by a flow, and a filter outlet 4 passable by a flow. A multiplicity of ducts 5, 6 passable by a flow are configured in the filter body 2. The ducts 5, 6 are configured so as to extend lying beside one another along a longitudinal axis L, wherein a flow along the longitudinal axis L takes place.

[0041] The ducts 5, 6 in an alternating manner have a closed end on the filter inlet 3 and on the filter outlet 4, respectively. The multiplicity of the ducts and the functional mode of the particle filter 1 will furthermore be described by means of a first duct 5 and of a second duct 6.

[0042] The first duct 5 has a first end 7 that is configured so as to face the filter inlet 3, and a second end 8 that is configured so as to face the filter outlet 4. The second duct 6 has a third end 9 that is configured so as to face the filter inlet 3, and a fourth end 10 that is configured so as to face the filter outlet 4. The second end 8 and the third end 9 are configured so as to be impassable by a flow. A flow transfer of the exhaust gas from the first duct 5 to the second duct 6 is performed by way of a common duct wall 11 that is configured between the first duct 5 and the second duct 6.

[0043] The ducts wall 11 is configured in a porous manner so as to be permeable to a flow, wherein the soot particles of the exhaust gas flowing through the duct wall 11 accumulate on the duct wall 11, or are deposited thereon, respectively. The exhaust gas flows through the particle filter 1 in the direction of the plotted arrows.

[0044] The ducts 5, 6 at the ends 8, 9 thereof that are impassable by a flow are closed with the aid of a stopper 12. In other words, this means that the ducts 5, 6 have in each case one duct portion 13 freely passable by a flow, and one duct portion 14 impassable by a flow.

[0045] The stopper 12 has an element cross section QE which corresponds to a cross section Q of the duct 5; 6. Since the ducts 5, 6 in the exemplary embodiment illustrated have an identical cross section, the element cross section QE likewise corresponds to a cross section Q of the second duct 6. The ducts 5, 6 in an exemplary embodiment (not illustrated in more detail) have dissimilar cross sections Q. This means that the stopper 12 has an element cross section QE that is configured so as to be adapted to the cross section Q of the respective duct 5, 6.

[0046] The element cross section QE of the stopper 12 in the exemplary embodiment illustrated is consistent across a length L of the stopper 12. The element cross section QE could likewise be variable across the length L thereof. For example, the stopper 12 in an exemplary embodiment (not illustrated in more detail) has a truncated-cone shape having an element cross section QE that varies across the length LE, in as far as the duct 5; 6 has a conical shape.

[0047] In the operation of the internal combustion engine the soot particles accumulate in the particle filter 1, wherein an effective flow cross section of the particle filter 1 is reduced over time. The reduction in the effective flow cross section leads to an increase of an exhaust gas back pressure of the internal combustion engine, said exhaust gas back pressure potentially leading to an increase in load cycle losses. This in turn, in the case of a constant output, would result in an increase of a fuel consumption of the internal combustion engine, or, in the case of an identical fuel consumption, in a reduction in the output of the internal combustion engine. A regeneration of the particle filter 1 is thus carried out so as to depend on a so-called loading of the particle filter 1.

[0048] In order for the particle filter 1 to be regenerated, said particle filter 1 has at least one heating element 15 which is disposed in the duct portion 14 impassable by a flow. The heating element 15 is composed of a functional material which in the case of an excess of air reacts in an exothermic manner, in other words releases heat and thus leads to a temperature increase in the particle filter 1.

[0049] The heating element 15 is configured in the form of the stopper 12 and replaces the latter. The heating element 15 could likewise also be configured as part of the stopper 12. Said heating element 15 is configured from a material which is configured so as to trigger an exothermic reaction when storing oxygen. In other words, this means that the heating element 15 by way of the molecular structure thereof releases heat in a self-acting manner in as far as a storage of oxygen is configured. This means that a release of reaction heat is performed.

[0050] The material is a solid material which can be present in at least two modifications. Said solid material in the rich operation of the internal combustion engine is at least partially present in a reduced modification, the first modification, and in a lean operation of the internal combustion engine transforms to an oxidized modification, the second modification. This solid material, also referred to as the functional material, is preferably a mixed oxide from cerium and zirconium oxides, optionally with further substances such as, for example, metals and/or earth metals, lanthanum, praseodymium, ytterbium, as well as aluminum oxide.

[0051] The less noble noble metals palladium and rhodium which also directly have an oxygen storage capability are also suitable. Said less noble noble metals do not oxidize at comparatively high temperatures, for example approximately 900 C., and thus do not store, and thus maintain the noble metallic state thereof. It is irrelevant herein whether this is an exhaust gas having a rich composition corresponding to the rich operation, or an exhaust gas having a lean composition corresponding to the lean operation of the internal combustion engine. According to FIG. 4, rhodium would be able to form rhodium oxide up to approx. 880 C. and thus be able to behave in a non-noble manner up to said temperature.

[0052] The functional material, according to the composition thereof, can be configured for the exothermic reaction in different temperature ranges. For example, a first material, for example palladium, has a composition having a reduction/oxidation capability in a low and medium temperature range up to approx. 700 C. A second material such as, for example TWC (three-way-catalyst) standard storage materials, has a composition additionally having an exothermic reaction in a high temperature range. In other words, this means that the first material is configured for reacting at low and medium temperatures present in the particle filter 1, and that the second material is configured for reacting above all of the temperatures present in the particle filter 1.

[0053] It goes without saying that all of the stoppers 12 can be replaced in each case by one heating element 15, on account of which the regeneration is improved.

[0054] A particle filter 1 having a plurality of heating elements 15 which are configured from a single material and/or a material mix is likewise expedient. The positioning of the heating element or heating elements 15, respectively, at the inlet side or the outlet side can also be chosen so as to be dependent on an installation situation of the particle filter 1 close to or remote from the motor.

[0055] In one preferred exemplary embodiment (not illustrated in more detail), all of the stoppers 12 of the particle filter 1 are in each case replaced by one heating element 15. A further exemplary embodiment (not illustrated in more detail) of the particle filter 1 according to the invention at the second end 8 has the heating element 15 configured from the first material, and at the third end 9 has the heating element 15 configured from the second material.

[0056] A further exemplary embodiment (not illustrated in more detail) of the particle filter according to the invention at second ends and third ends which are more remote from the central longitudinal axis has heating elements from a first material. At the second ends and the third ends which are closer to the central longitudinal axis, said exemplary embodiment has heating elements from a second material, or no heating elements at all.

[0057] A further heating element 15 could also be disposed in the duct portion 13 passable by a flow. Said heating element 15 could be configured from a further material that is dissimilar to the first material and the second material. In other words, this means said heating element 15 is composed from a further material having an oxygen storage capability that is dissimilar to that of the first material and to that of the second material.

LIST OF REFERENCE SIGNS

[0058] 1 Particle filter [0059] 2 Filter body [0060] 3 Filter inlet [0061] 4 Filter outlet [0062] 5 First duct [0063] 6 Second duct [0064] 7 First end [0065] 8 Second end [0066] 9 Third end [0067] 10 Fourth end [0068] 11 Duct wall [0069] 12 Stopper [0070] 13 Duct portion passable by a flow [0071] 14 Duct portion impassable by a flow [0072] 15 Heating element [0073] L Longitudinal axis [0074] LE Length [0075] L1 Profile [0076] Q Duct cross section [0077] QE Element cross section [0078] T Temperature [0079] T0 Inlet temperature [0080] T1 First temperature profile [0081] T2 Second temperature profile [0082] T3 Third temperature profile [0083] t Time [0084] t0 Temperature profile before operational changeover [0085] t1 Temperature profile after operational changeover [0086] t2 Temperature profile after operational changeover [0087] t3 Temperature profile after operational changeover [0088] t4 Temperature profile after operational changeover [0089] Combustion air ratio