EXHAUST SYSTEM FOR AN INTERNAL COMBUSTION ENGINE AND METHOD FOR OPERATING SUCH AN EXHAUST SYSTEM

Abstract

An exhaust system for an internal combustion engine is connected to an outlet of the internal combustion engine and has a particulate filter. A differential pressure line for ascertaining the particulate filter load connects a section of the exhaust passage upstream from the particulate filter and a section of the exhaust passage downstream from the particulate filter to a differential pressure sensor. At an end of the differential pressure line facing the exhaust passage, a reservoir which serves to collect condensate protrudes into the exhaust passage and can be heated up by the exhaust gas in the exhaust passage. Due to the heating of the reservoir, the liquid that has collected in the reservoir evaporates and can be introduced in gaseous form into the exhaust passage through an opening in the reservoir, so that the risk of droplet formation in the exhaust passage is avoided.

Claims

1. An exhaust system (12) for an internal combustion engine (10), comprising: an exhaust passage (18), a particulate filter (16) arranged in the exhaust passage (18), and a differential pressure line (20) which connects a first section (22) of the exhaust passage (18) upstream from the particulate filter (16) and/or a second section (24) of the exhaust passage (18) downstream from the particulate filter (16) to a differential pressure sensor (84), wherein, at an end (38) of the differential pressure line (20) facing the exhaust passage (18), a reservoir (26) that is fluidically connected to the exhaust passage (18) is formed which protrudes into the exhaust passage (18), whereby the reservoir (26) can be heated up by the exhaust gas of the internal combustion engine (10) in such a way that liquid (28) that has collected in the reservoir (26) evaporates before exiting into the exhaust passage (18), after which it is introduced in gaseous form into the exhaust passage (18).

2. The exhaust system (12) according to claim 1, wherein a NO.sub.x sensor (50) that detects the nitrogen oxide concentration, a temperature sensor (86) or a particle sensor (88) is arranged in the exhaust system (12) downstream from the reservoir (26).

3. The exhaust system (12) according to claim 1, wherein an opening (30) or a slit (32) is formed on the reservoir (26) so that the liquid (28) that has collected in the reservoir (26) can be released into the exhaust passage (18) in a controlled manner.

4. The exhaust system (12) according to claim 3, wherein the opening (30) or the slit (32) is configured such that a liquid (28) is prevented from exiting the opening (30) or the slit (32) due to gravity, whereas a gaseous medium can escape into the exhaust passage (18) through the opening (30) or the slit (32).

5. The exhaust system (12) according to claim 1, wherein a trailing edge (34) is formed on the reservoir in order to prevent a volume flow from the reservoir (26) from accumulating on a wall (36) of the exhaust passage (18).

6. The exhaust system (12) according to claim 1, wherein the downstream end (38) of the differential pressure line (20) opens up into an exhaust-gas funnel (48) directly downstream from a filter body (40) of the particulate filter (16).

7. The exhaust system (12) according to claim 1, wherein the differential pressure line (20) branches off from the exhaust passage (18) upstream from a branch (44) for a low-pressure exhaust-gas return line (46) and it once again opens up into the exhaust passage (18) downstream from the branch (44) for the low-pressure exhaust-gas return line (46).

8. The exhaust system (12) according to claim 1, wherein the reservoir (26) is made of sheet metal (42), a cast part, a lathed part or a milled part.

9. The exhaust system (12) according to claim 7, wherein the metal sheet (42), the cast part, the lathed part or the milled part is screwed into the exhaust passage (18).

10. The exhaust system (12) according to claim 7, wherein the metal sheet (42), the cast part, the lathed part or the milled part is positively and/or non-positively joined to the differential pressure line (20).

11. The exhaust system (12) according to claim 2, wherein the NO.sub.x sensor (50), the temperature sensor (86) or the particle sensor (88) is arranged at a distance (D) of 120 mm to 1500 mm downstream from the filter body (40) of the particulate filter (16).

12. A method for the after-treatment of the exhaust gas of an internal combustion engine (10), comprising: conveying the exhaust gas of the internal combustion engine (10) through an exhaust system (12) having an exhaust passage (18), cleaning the exhaust gas of the internal combustion engine (10) by a particulate filter (16), whereby the exhaust system (12) has a differential pressure line (20) that connects a first section (22) of the exhaust passage (18) upstream from the particulate filter (16) and/or a second section (24) of the exhaust passage (18) downstream from the particulate filter (16) to a differential pressure sensor (84), wherein, at an end (38) of the differential pressure line facing the exhaust passage (18), a reservoir (26) that is fluidically connected to the exhaust passage (18) is formed which protrudes into the exhaust passage (18), whereby the reservoir (26) is heated up by the exhaust gas of the internal combustion engine (10) in such a way that liquid (28) that has collected in the reservoir (26) evaporates before exiting into the exhaust passage (18), after which it is introduced in gaseous form into the exhaust passage (18).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention will be explained below on the basis of embodiments with reference to the accompanying drawings. Identical components or components having the same function are designated in the figures by the same reference numerals. The following is shown:

[0023] FIG. 1 is an embodiment of an internal combustion engine with an exhaust system according to the invention, in a schematic view;

[0024] FIG. 2 is an exhaust system according to the invention for an internal combustion engine, in a three-dimensional view;

[0025] FIG. 3 is an end section of a differential pressure line facing the exhaust passage, with a reservoir;

[0026] FIG. 4 is another view of a section of an exhaust system according to the invention;

[0027] FIG. 5 is a section of an exhaust system according to the invention, showing the particulate filter as well as an adjoining section of the exhaust passage downstream from the particulate filter;

[0028] FIG. 6 is an exhaust system according to the invention, with a particulate filter and a differential pressure line, in a three-dimensional view.

DETAILED DESCRIPTION OF THE INVENTION

[0029] FIG. 1 shows an embodiment of an internal combustion engine 10 with an exhaust system 12 according to the invention. The internal combustion engine 10 is preferably configured as a diesel engine that is self-ignited through compression. As an alternative, the internal combustion engine 10 can also be configured as a gasoline engine that is externally ignited by means of an ignition device, especially as a gasoline engine with direct fuel injection. The internal combustion engine 10 has an outlet 52 that is connected to the exhaust system 12. The exhaust system 12 comprises a first catalytic converter 14, preferably a diesel oxidation catalytic converter or a NO.sub.x storage catalytic converter, and a particulate filter 16 that is installed downstream from the first catalytic converter 14 and that preferably has a coating 66 for the selective catalytic reduction of nitrogen oxides (SCR coating). The exhaust system 12 also has an exhaust passage 18 that connects the outlet 52 to a tailpipe 78 of the exhaust system 12. In this context, a first section 22 of the exhaust passage 18 connects the outlet 52 of the internal combustion engine 10 to the particulate filter 16. In this first section 22, a turbine 56 of an exhaust-gas turbocharger 54 is preferably arranged downstream from the outlet 52 and upstream from the first catalytic converter 14. Moreover, a metering element 60 that serves to meter in a reducing agent 64, especially an aqueous urea solution stored in a reducing agent tank 62, is arranged in the first section 22 of the exhaust passage 18.

[0030] The particulate filter 16 has one inlet and two outlets. In this context, the first outlet of the particulate filter 16 is connected to a low-pressure exhaust-gas return line 46 by means of which the exhaust gas can be admixed with fresh air upstream from a compressor of the exhaust-gas turbocharger 54 that is driven by the turbine 56 in order to lower the raw emissions when the fuel-air mixture is being burned in the combustion chambers of the internal combustion engine 10. The second outlet of the particulate filter 16 is connected to a second section 24 of the exhaust passage 18 of the exhaust system 12, said passage also being referred to as the main passage. The second section 24 of the exhaust passage 18 connects the particulate filter 16 to the tailpipe 78 of the exhaust system 12. An additional catalytic converter 76, especially an additional catalytic converter for the selective catalytic reduction of nitrogen oxides, can be arranged in the main passageespecially in a place in the undercarriage of the motor vehicle where the internal combustion engine 10 with an exhaust system 12 according to the invention is installedin order to achieve an additional cleaning of the exhaust gas. As an alternative, the additional catalytic converter 76 can also widen the temperature window within which at least one of the two exhaust after-treatment components 18, 76 for the selective catalytic reduction of nitrogen oxides allows an efficient conversion of nitrogen oxides.

[0031] Preferably, the first catalytic converter 14 and the particulate filter 16 are both arranged near the engine. In this context, the term arranged near the engine refers to an arrangement having an exhaust-gas travel distance of 80 cm at the maximum, preferably of 60 cm at the maximum, starting from the outlet 52 of the internal combustion engine 10. In this context, if the particulate filter 16 is configured with an SCR coating 66, it should be ensured that the mixing segment between the first catalytic converter 14 and the particulate filter 16 is long enough to allow the reducing agent 64 that has been metered into the exhaust passage 18 to mix with the exhaust gas before entering the particulate filter 16. In order to shorten the length of the mixing segment, the section of the exhaust passage 18 between the first catalytic converter 14 and the particulate filter 16 has a bend of approximately 60, as a result of which the deflection causes the exhaust gas to swirl, and consequently, the reducing agent 64 is uniformly distributed in the exhaust passage 18 over a relatively short mixing segment. Moreover, the section of the exhaust passage 18 can have a mixing element 80 to further improve the thorough mixing of the exhaust gas stream with the reducing agent 64. At the particulate filter 16 downstream from the filter body 40 in the flow direction of the exhaust gas through the particulate filter 16, there is a branch 44 where the exhaust passage 18 branches off into a low-pressure exhaust-gas return line 46 and a main passage that connects the particulate filter 16 to the tailpipe 78 of the exhaust system 12. For this purpose, downstream from the filter body 40, the particulate filter 16 has an exhaust-gas funnel 48 that branches off into a second funnel 68 and into a third funnel 72. In this context, the second funnel 68 is connected to the low-pressure exhaust-gas return line 46. Moreover, in order to prevent the penetration of soot particles into the low-pressure exhaust-gas return line 46, the second funnel 68 has a filter element 70. The third funnel 72 has a larger diameter than the second funnel 68 and it connects the particulate filter 16 to the main passage of the exhaust system 12.

[0032] Due to the fact that exhaust-gas legislation is becoming increasingly stringent, particularly with respect to nitrogen oxide emissions, engine-internal measures have to be combined with measures pertaining to the exhaust after-treatment. One way to improve the raw emissions of the internal combustion engine 10 consists of admixing exhaust gas with the fresh air in order to reduce the formation of nitrogen oxide emissions. In this process, it is advantageous for the returned exhaust gas to be as cool as possible. For this reason, a low-pressure exhaust-gas return cooler can be arranged in the low-pressure exhaust-gas return line 46. In addition, an exhaust-gas valve 74 can be arranged in the main passage of the exhaust system 12 and it can influence the amount of exhaust gas fed to the low-pressure exhaust-gas return line 46.

[0033] The internal combustion engine 10 also comprises a control unit 58 with which the amount of fuel fed to the combustion chambers of the internal combustion engine 10 can be controlled or regulated. Moreover, the control unit 58 serves to actuate the exhaust system according to the invention and, for example, to control the amount of reducing agent 56 that is metered into the exhaust passage 18 or to control the regeneration of the particulate filter 16.

[0034] In FIG. 2, the exhaust system 12 according to the invention of an internal combustion engine 10 is shown in a three-dimensional view. Thanks to the exhaust-gas 12 according to the invention, a minimum exhaust-gas counter-pressure can be implemented in a design that is compact and space-saving. In this context, the exhaust system 12 has an exhaust-gas turbocharger 54 which is arranged directly adjoining the outlet 52 of the internal combustion engine 10 and whose turbine 56 is powered by exhaust gas from the internal combustion engine 10. The exhaust system 12 has a differential pressure line 20 that connects the first section 22 of the exhaust passage 18 upstream from the particulate filter 16 to the first inlet 94 of a differential pressure sensor 84 via a first section 90 of the differential pressure line 20. A second section 24 of the exhaust passage 18 is connected to a second inlet 96 of the differential pressure sensor 84 via a second section 92 of the differential pressure line 20. The differential pressure sensor 84 also has an electric contact 98 by means of which the detected pressure signal can be relayed to the control unit 58, where it is then processed. At the downstream end 38 of the differential pressure line 20, there is a reservoir 26 in which the condensate being formed in the differential pressure line 20 can accumulate. A NO.sub.x sensor is provided downstream from the particulate filter 16 and downstream from the opening of the differential pressure line 20. The downstream end 38 of the differential pressure line 20 is depicted in greater detail in FIG. 3.

[0035] FIG. 3 shows the downstream end 38 of the differential pressure line 20 facing the exhaust passage 18. The differential pressure line 20 is affixed to the exhaust passage 18 by means of a connecting piece 82 on the wall 36.

[0036] A reservoir 26 with a collecting area for the condensate as well as with at least one opening 30 or one slit 32 is formed at the downstream end 38 of the differential pressure line 20. Liquid 28 that has condensed out can be captured in this collecting area so that it does not drip into the exhaust passage 18 in an uncontrolled manner. Here, the reservoir 26 protrudes into the exhaust passage 18 in order to promote the heating up and evaporation of the liquid 28 that has collected in the reservoir 26. In this context, the slit 32 or the opening 30 is arranged in such a way that the pressure in the segment of the exhaust passage can be ascertained. Moreover, the slit 32 or the opening is arranged in such a manner that the liquid 28 has to rise from the collecting area against the force of gravity in order to exit from the reservoir and to enter the exhaust passage 18, so that an uncontrolled dripping of the condensate into the exhaust passage 18 is prevented. On the reservoir 26, there is a trailing edge 34 in order to promote the mixing of the evaporated condensate with the exhaust gas as well as to prevent large amounts of the condensate from collecting on the wall 36 of the exhaust passage 18, where it could condense again under unfavorable operating conditions.

[0037] FIG. 4 shows another embodiment of an exhaust system 12 according to the invention, whereby, for the sake of clarity, only the section 24 downstream from the particulate filter 16 is depicted. A connecting piece 82 for the differential pressure line 20 is formed on the second section 24 of the exhaust passage 18. Downstream from the filter body 40 of the particulate filter 16 and downstream from the connecting piece 82, a NO.sub.x sensor is arranged on the exhaust passage 18 in order to detect the nitrogen oxide concentration downstream from the particulate filter 16 and thus to check the function of the exhaust after-treatment in the case of a particulate filter 16 having an SCR coating 66. As an alternative or in addition, the NO.sub.x sensor 50 can also be used to detect the nitrogen oxide concentration upstream from a second catalytic converter 76 (not shown in FIG. 4) where it meters an appropriate amount of reducing agent into the exhaust passage 18. The NO.sub.x sensor 50 is installed at a distance of approximately 150 mm downstream from the filter body 40 of the particulate filter 16, thus translating into a compact design of the exhaust system 12 according to the invention.

[0038] FIG. 5 shows another embodiment of an exhaust system 12 according to the invention. Here, the exhaust passage 18 branches off at the exhaust-gas funnel 48 into the low-pressure exhaust-gas return line 46 and into a main passage of the exhaust system 12 where the differential pressure line 20 is attached by means of a connecting piece 82. Here, the reservoir 26 consists of a metal sheet 42 that is inserted into the exhaust passage 18 and preferably screwed or welded to it.

[0039] During operation and especially after operation of the exhaust system 12, water vapor and/or reducing agent can condense out in the differential pressure line and it can then accumulate in the form of liquid droplets on the wall of the differential pressure line and can accumulate in the reservoir 26 due to the force of gravity. In this scenario, at low ambient temperatures and after the internal combustion engine 10 has been switched off, the condensate might also freeze. The collecting area of the reservoir 26 prevents liquid condensate droplets or ice from penetrating into the exhaust passage 18 downstream from the particulate filter 16, where they cause damage, in particular damage to the NO.sub.x sensor 50 located directly downstream from the reservoir 26. Due to the hot exhaust gas, the condensate captured in the collecting area of the reservoir 26 evaporates and then, in the form of vapor, gets into the exhaust passage through the opening 30 or the slit 32, thereby ruling out mechanical damage to components situated downstream from the reservoir 26. The reservoir 26 can be inexpensively made as a one-piece stamped-bent part or as deep-drawn part, although it is also possible to assemble the reservoir 26 out of several parts and to join these using a positive, non-positive or integrally bonded technique.

[0040] FIG. 6 shows another embodiment of an exhaust system according to the invention with a particulate filter 16. With an essentially identical structure as shown in FIG. 2, the connection of the differential pressure line 20 to the exhaust passage 18 upstream and downstream from the particulate filter 16 is shown in this view. Here, a first section 90 of the differential pressure line 20 connects the first section 22 of the exhaust passage 18 to a first inlet 94 of the differential pressure sensor 84. A second section 92 of the differential pressure line 20 connects the second section 24 of the exhaust passage 18 downstream from the particulate filter 16 to a second inlet 96 of the differential pressure sensor 84. As a result, a pressure differential can be ascertained in the exhaust passage 18 before and after the particulate filter 16, said value serving as the measure of the loading of the particulate filter 16. The differential pressure sensor 84 is also provided with an electric contact 98 in order to transmit the pressure signal from the differential pressure sensor 84 to the control unit 58.

LIST OF REFERENCE NUMERALS

[0041] 10 internal combustion engine [0042] 12 exhaust system [0043] 14 first catalytic converter [0044] 16 particulate filter [0045] 18 exhaust gas passage [0046] 20 differential pressure line [0047] 22 first section of the exhaust passage [0048] 24 second section of the exhaust passage [0049] 26 reservoir [0050] 28 liquid [0051] 30 opening [0052] 32 slit [0053] 34 trailing edge [0054] 36 wall [0055] 38 downstream end of the differential pressure line [0056] 40 filter body [0057] 42 metal sheet [0058] 44 branch [0059] 46 low-pressure exhaust-gas return line [0060] 48 exhaust-gas funnel [0061] 50 NO.sub.x sensor [0062] 52 outlet [0063] 54 exhaust-gas turbocharger [0064] 58 turbine [0065] 58 control unit [0066] 60 metering module [0067] 62 reducing agent tank [0068] 64 reducing agent [0069] 66 SCR coating [0070] 68 second funnel [0071] 70 filter element [0072] 72 third funnel [0073] 74 exhaust-gas valve [0074] 76 additional catalytic converter [0075] 78 tailpipe [0076] 80 exhaust-gas mixer [0077] 82 connecting piece [0078] 84 differential pressure sensor [0079] 86 temperature sensor [0080] 88 particle sensor [0081] 90 first section of the differential pressure line [0082] 92 second section of the differential pressure line [0083] 94 first inlet of the differential pressure sensor [0084] 96 second inlet of the differential pressure sensor [0085] 98 electric contact [0086] D distance