Exhaust aftertreatment device with two catalyst elements and one electric heating element

Abstract

Exhaust aftertreatment device (11) with a housing (12) and a catalyst assembly comprising a first catalyst element (13), a second catalyst element (14) and an electric heating element (15) arranged between the catalyst elements (13, 14), wherein the catalyst assembly is accommodated within a receiving section (12c) of the housing (12), characterized in that the volume of the first catalyst element (13) is at least 20% and at most 50% of the effective volume of the catalyst assembly.

Description

[0001] The invention relates to an exhaust gas aftertreatment device having a housing and a catalyst device accommodated within the housing, which comprises a first catalyst element, a second catalyst element and an electrical heating element arranged between the catalyst elements.

[0002] The emission limits applicable to internal combustion engines are becoming increasingly stricter. This applies particularly to internal combustion engines designed to power motor vehicles. In order to comply with these emission limits, the exhaust aftertreatment devices integrated into the exhaust systems of these internal combustion engines must be capable of converting emissions as quickly as possible after a cold start. This requires that the exhaust aftertreatment devices reach their light-off temperatures (also known as "light-off temperatures") as quickly as possible after a cold start of the internal combustion engine, at which point sufficient effectiveness for exhaust aftertreatment can be assumed.

[0003] It is known that exhaust aftertreatment devices can be temporarily and specifically heated. This can be achieved both through engine-related measures that cause an internal combustion engine to emit exhaust gas at a relatively high exhaust temperature, as well as through active heating measures, for example, using electric heaters.

[0004] WO 2020 / 152138 A1 discloses an exhaust gas aftertreatment system for an internal combustion engine comprising an oxidation catalyst, an SCR catalyst located downstream thereof, and a particulate filter located downstream thereof. Furthermore, an electric heating element is provided, which is configured to heat the exhaust gas and is positioned such that it heats at least a portion of the oxidation catalyst. The oxidation catalyst comprises at least two spatially separated coating sections with different coatings. The heating element can be integrated into the oxidation catalyst and arranged between the coating sections.

[0005] The invention is based on the object of keeping the pollutant emissions of an internal combustion engine low, especially after a cold start.

[0006] This problem is solved by the subject matter of the patent claims.

[0007] According to the invention, an exhaust gas aftertreatment device is provided, which comprises a (single-part or multi-part) housing and a catalyst device, wherein the catalyst device has a first catalyst element, a second catalyst element, and an electric heating element arranged between the catalyst elements. The catalyst device is accommodated within a receiving section of the housing. The volume of the first catalyst element is at least 20% and at most 50%, preferably at most 40%, particularly preferably at most 30% of the effective volume of the catalyst device, wherein this effective volume corresponds to the sum of the volumes delimited by the outer sides of the catalyst elements and the heating element. The second catalyst element can preferably have a volume of at least 40% and at most 60% of the effective volume of the catalyst device.

[0008] The electrical heating element is primarily or exclusively intended and configured to convert supplied electrical energy into thermal energy. This can preferably be or comprise a resistance heating element that generates thermal energy as a result of resistance losses during a current flow.

[0009] According to the invention, an internal combustion engine is also provided which comprises an internal combustion engine which forms at least one combustion chamber and an exhaust system into which such an exhaust gas aftertreatment device according to the invention is integrated.

[0010] The arrangement of the heating element between the catalyst elements leads to advantageous use of the thermal energy released by the heating element during its operation, in that the thermal energy radiated by both sides of the heating element is used directly to heat the catalyst elements. The inventive dimensioning of the first catalyst element in particular can bring about advantageous distribution of the thermal energy released by the heating element among the catalyst elements. The preferably smaller dimensioning of the first catalyst element compared to the second catalyst element advantageously takes into account that the greater part of the thermal energy released by the heating element is supplied to the second catalyst element as a result of the exhaust gas flowing through the exhaust gas aftertreatment device.This allows for an advantageous, even distribution of heat energy across the catalyst elements.

[0011] Furthermore, the arrangement of the heating element between the catalyst elements can shield other components of the exhaust system from the heating element, which could otherwise lead to thermal overload or malfunction. This can apply in particular to a temperature sensor, which in an internal combustion engine according to the invention can preferably be integrated into the exhaust system upstream (with respect to the flow direction of exhaust gas in the exhaust system starting from the internal combustion engine), in particular directly (i.e., at most with the interposition of a pipe carrying only the exhaust gas) upstream of the exhaust gas aftertreatment device, and can serve to measure the temperature of the exhaust gas.The shielding of the temperature sensor from the heating element by the first catalyst element can prevent falsification of such a measurement of the temperature sensor, which could otherwise be the result of heating by thermal energy released by the heating element.

[0012] According to a preferred embodiment of an exhaust gas aftertreatment device according to the invention, the housing can have no opening cross-sectional area along the length of the receiving section, or a reduction of its opening cross-sectional area of ​​a maximum of 25%, preferably a maximum of 10%. This allows for advantageous flow of the exhaust gas through the exhaust gas aftertreatment device and also advantageous transfer of the thermal energy released by the heating element to the catalyst elements.

[0013] The same purpose can be served if, as is preferably provided, the sizes of the downstream side of the first catalyst element and the upstream side of the heating element differ by a maximum of 25%, preferably by a maximum of 10%, particularly preferably by a maximum of 5% and / or the sizes of the downstream side of the heating element and the upstream side of the second catalyst element differ by a maximum of 25%, preferably by a maximum of 10%, particularly preferably by a maximum of 5%. The “downstream side” is understood to mean that side of the first catalyst element and the heating element via which the exhaust gas leaves the respective element during the intended flow. The “upstream side”, on the other hand, is understood to mean that side of the heating element and the second catalyst element via which the exhaust gas enters the respective element during the intended flow.

[0014] According to a preferred embodiment of an exhaust gas aftertreatment device according to the invention, the first catalyst element can comprise an oxidation catalyst and / or a nitrogen oxide storage catalyst, and / or the second catalyst element can comprise an oxidation catalyst and / or a nitrogen oxide storage catalyst. Such catalysts can benefit particularly advantageously from heating by means of the electric heating element.

[0015] Furthermore, it can preferably be provided that the heating element has a volume that is between 5% and 40% of the effective volume of the catalytic converter device. A heating element dimensioned in this way can advantageously be adapted to the requirements of the catalytic converter elements. By varying the possible current intensities, different heating outputs that the heating element can provide result. In one embodiment, if installation space is restricted, the heating element can be operated at a high current intensity at the lower end of the specified volume. This allows a high heating output to be achieved with a relatively small heating element volume. In another embodiment, if sufficient installation space is available, the heating element can be operated at a low current intensity at the upper end of the volume. This allows premature aging due to high current intensities to be avoided.In yet another embodiment, if sufficient space is available, the heating element at the upper end of the volume can be operated at a high current. This allows for particularly high heat requirements of the catalysts to be met.

[0016] Preferably, it can be provided that a gap or a free space is formed between the heating element on the one hand and the first catalyst element and the second catalyst element on the other hand, so that the catalyst elements do not lie directly against the heating element. This can prevent local thermal overloading of the catalyst elements during operation of the heating element and / or an electrical short circuit in the electrical power supply of the heating element. The volume of the gap (total) can preferably be at least 5% and at most 10% of the total volume of the catalyst device. The total volume of the catalyst device is understood to be the sum of the effective volume of the catalyst device and the volume of the gap. The volume of the gap refers to the internal volume of the housing in the longitudinal sections in which the gaps are located.The widths (extensions along the course of the receiving section or in the flow direction of the exhaust gas) of the gaps can preferably be between 2 mm and 15 mm.

[0017] At least one of the gaps can be continuous or uninterrupted, whereby a complete separation between the corresponding components can be realized. At least one of the gaps can also be interrupted, i.e. bridged by at least one connecting element, which in particular also serves as a mechanically supporting connection between the corresponding components. A connecting element that interrupts such a gap can preferably be designed to be relatively thermally conductive, whereby a transfer of thermal energy between the components, one of which is the heating element and the other one of the catalyst elements, can be advantageously influenced. Furthermore, such a connecting element can advantageously be electrically insulating (i.e.The gap between the first catalyst element and the heating element can be designed to be electrically conductive (i.e., not electrically conductive to a relevant extent), thereby preventing an electrical short circuit in the electrical power supply of the heating element. In particular, it can be provided that the gap between the first catalyst element and the heating element is continuous and the gap between the heating element and the second catalyst element is interrupted.

[0018] Preferably, the total volume of the catalytic converter device can be between 0.5 l and 6 l, preferably between 1.5 l and 5 l, particularly preferably between 2 l and 4 l. This represents advantageous dimensioning, particularly in combination with an internal combustion engine whose total displacement is between 1 l and 6 l. The “displacement volume” is understood to mean the change in the volume of a combustion chamber of the internal combustion engine during a combustion cycle in this combustion chamber. The “total displacement volume” then represents the sum of the displacement volumes of all combustion chambers of the internal combustion engine. If the internal combustion engine only comprises one combustion chamber, its displacement volume corresponds to the total displacement volume of the internal combustion engine.

[0019] Preferably, the heating element can be configured for an electrical operating voltage of at least 12 V, preferably at least 24 V, particularly preferably at least 36 V, which can enable sufficient heating power of the heating element to be achieved with relatively low current intensities. Furthermore, the heating element can preferably be configured for an electrical operating voltage of a maximum of 60 V, preferably of a maximum of 54 V, particularly preferably of a maximum of 52 V, because an operating voltage exceeding 60 V can place considerably greater demands on electrical protection, which can be associated with correspondingly high additional costs.

[0020] For the best possible adaptation of the exhaust gas aftertreatment device to the maximum exhaust gas mass flow flowing through it, it can preferably be provided that the volume of the second catalyst element is at least 50% and / or at most 100% of the total displacement of the internal combustion engine.

[0021] The internal combustion engine of an internal combustion engine according to the invention can, in particular, be a (compression-ignition and quality-controlled) diesel engine. However, it is also possible for the internal combustion engine to be a (spark-ignition and quantity-controlled) gasoline engine or a functional combination of a diesel and a gasoline engine, e.g., a homogeneous compression ignition internal combustion engine. The internal combustion engine can be operated with liquid fuel (i.e., diesel or gasoline) and / or with a gaseous fuel (in particular, natural gas, LNG, or LPG).

[0022] The invention further relates to a motor vehicle, in particular a wheel-based and non-rail-based motor vehicle (preferably a car or a truck), with an internal combustion engine according to the invention. The internal combustion engine of the internal combustion engine can be provided, in particular, for the (direct or indirect) provision of the traction drive power for the motor vehicle.

[0023] The invention is explained in more detail below with reference to an exemplary embodiment shown in the drawings. The sole drawing shows: Fig. 1: an internal combustion engine according to the invention for a motor vehicle in a simplified representation.

[0024] This internal combustion engine comprises an internal combustion engine 1, which is designed, for example, in the form of a reciprocating piston engine with four cylinder openings 2 arranged in series. The cylinder openings 2, with reciprocating pistons 3 guided therein and a cylinder head, each delimit a combustion chamber 4. During operation of the internal combustion engine 1 and thus of the internal combustion engine, fresh gas is supplied to these combustion chambers 4 via a fresh gas line 5, with the supply of fresh gas being controlled by inlet valves 6 assigned to the individual combustion chambers 4. The fresh gas is exclusively or mainly air that is sucked in from the environment. Exhaust gas is generated during the combustion of mixture quantities consisting of the fresh gas and fuel injected directly into the combustion chambers 4 via fuel injectors 7.This exhaust gas is discharged via an exhaust system 8 of the internal combustion engine, with the discharge of the exhaust gas from the individual combustion chambers 4 being controlled by exhaust valves 9. The exhaust gas flows through one or more exhaust aftertreatment devices integrated into the exhaust system 8, which are designed to remove components of the exhaust gas that are considered pollutants and / or to convert them into harmless components. In the . Fig. 1 shows only one exhaust gas aftertreatment device 11 configured according to the invention. One or more additional exhaust gas aftertreatment devices (not shown) can be integrated into the exhaust system 8 upstream and / or downstream of this exhaust gas aftertreatment device 11 according to the invention. For example, a particulate filter and / or an SCR catalyst can be provided downstream of the exhaust gas aftertreatment device 11.

[0025] The internal combustion engine can be designed with turbocharging, in which case a fresh gas compressor (not shown) would be integrated into the fresh gas line 5. If the fresh gas compressor were part of an exhaust gas turbocharger, this exhaust gas turbocharger would also include an exhaust gas turbine (not shown) integrated into the exhaust gas line 8. Exhaust gas flowing through the exhaust gas turbine would then result in a rotating drive of a turbine impeller, which is connected in a rotationally driving manner to a compressor impeller of the fresh gas compressor, so that the fresh gas compressor would ultimately be driven by the exhaust gas turbine.

[0026] The exhaust gas aftertreatment device 11 comprises a housing 12 having an inlet section 12a and an outlet section 12b. Furthermore, the housing 12 forms a receiving section 12c, within which a catalyst device is arranged.

[0027] The catalyst device comprises a first catalyst element 13, a second catalyst element 14, and an electric heating element 15, which is positioned to form a gap 16 between the catalyst elements 13, 14. The catalyst elements 13, 14 and the heating element 15 are each designed to allow the exhaust gas to flow through them and completely fill the housing 12 in the area occupied by them, ie their cross-sectional areas essentially correspond to the opening cross-sectional areas of the housing 12 in the respective area.

[0028] The inlet section 12a and the outlet section 12b are each connected to an exhaust pipe 10 of the exhaust system 8. The opening cross-sectional areas of the inlet section 12a and the outlet section 12b are significantly smaller than the opening cross-sectional areas of the housing 12 within the receiving section 12c. In particular, the respective end-side opening cross-sectional areas of the inlet section 12a and the outlet section 12b can amount to a maximum of 50%, preferably a maximum of 25% of the opening cross-sectional areas in the receiving section 12c of the housing 12. The opening cross-sectional areas of the housing 12 are preferably constant over the course of the receiving section 12c, as shown in the Fig.1. If this is not the case, the specified size ratio refers to the smallest of the opening cross-sectional areas of the housing 12 in the receiving section 12c. Between the inlet section 12a and the receiving section 12c, the housing 12 forms a conically widening distribution section 12d and between the receiving section 12c and the outlet section 12b, a conically tapered collecting section 12e.

[0029] The catalyst elements 13, 14 can each comprise an oxidation catalyst and / or a nitrogen oxide storage catalyst. These catalysts can each be formed as a coating on a support element provided with through-openings to allow flow. The catalyst elements 13, 14, the heating element 15, and the gap 15 are dimensioned as claimed in the patent claims. List of reference symbols 1 combustion engine 2 cylinder opening 3 reciprocating pistons 4 combustion chamber 5 Fresh gas line 6 Inlet valve 7 Fuel injector 8 Exhaust system 9 Exhaust valve 10 exhaust pipe 11 Exhaust aftertreatment device 12 housings 12a Inlet section of the housing 12b Outlet section of the housing 12c Housing receiving section 12d Distribution section of the housing 12e Collecting section of the housing 13 first catalyst element 14 second catalyst element 15 electric heating element 16 gap QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2020 / 152138 A1

[0004]

Claims

[1] Exhaust gas aftertreatment device (11) with a housing (12) and a catalyst device comprising a first catalyst element (13), a second catalyst element (14) and an electric heating element (15) arranged between the catalyst elements (13, 14), wherein the catalyst device is accommodated within a receiving section (12c) of the housing (12), characterized by that the volume of the first catalyst element (13) is at least 20% and at most 50% of the effective volume of the catalyst device. [2] Exhaust gas aftertreatment device (11) according to claim 1, characterized by that the first catalyst element (13) comprises an oxidation catalyst and / or a nitrogen oxide storage catalyst and / or the second catalyst element (14) comprises an oxidation catalyst and / or a nitrogen oxide storage catalyst. [3] Exhaust gas aftertreatment device (11) according to one of the preceding claims, characterized bythat the volume of the heating element (15) is at least 5% and at most 40% of the effective volume of the catalyst device. [4] Exhaust gas aftertreatment device (11) according to one of the preceding claims, characterized by that the volume of the second catalyst element (14) is at least 40% and at most 60% of the effective volume of the catalyst device. [5] Exhaust gas aftertreatment device (11) according to one of the preceding claims, characterized by that a gap (16) is formed between the heating element (15) on the one hand and the first catalyst element (13) and the second catalyst element (14) on the other hand, wherein the volume of the gap (16) is at least 5% and at most 10% of the total volume of the catalyst device. [6] Exhaust gas aftertreatment device (11) according to claim 5, characterized bythat at least one of the gaps (16) is continuous and / or at least one of the gaps (16) is bridged by at least one connecting element. [7] Exhaust gas aftertreatment device (11) according to one of the preceding claims, characterized by that the total volume of the catalyst device is between 1 l and 6 l. [8] Exhaust gas aftertreatment device (11) according to one of the preceding claims, characterized by that the heating element (15) is designed for an operating voltage of at least 12 V and a maximum of 60 V. [9] Internal combustion engine with an internal combustion engine (1) which forms at least one combustion chamber (4), and with an exhaust system (8) into which an exhaust gas aftertreatment device (11) according to one of the preceding claims is integrated. [10] Internal combustion engine according to claim 9, characterized bythat the volume of the second catalyst element (14) is at least 50% and / or a maximum of 100% of a total displacement of the internal combustion engine (1)

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