Catalytic converter for exhaust gas aftertreatment, with improved structure

Abstract

The invention relates to a catalytic converter (1) for aftertreatment of exhaust gases of an internal combustion engine, comprising a honeycomb body (2) wound from at least one metal foil, wherein the honeycomb body (2) has a central axis which extends along its axial extent from a gas inlet side (6) of the honeycomb body (2) to a gas outlet side (7) of the honeycomb body (2), and the honeycomb body (2) has a plurality of flow channels, through which gas can flow from a gas inlet side (6) of the honeycomb body (2) to a gas outlet side (7), wherein the honeycomb body (2) is divided into individual axial sections (4, 5) along its axial extent, along which the central axis runs, wherein the axial sections (4, 5) have flow channel sections which run at different angles to the central axis.

Description

[0001] Description

[0002] Catalyst for exhaust aftertreatment with improved structure

[0003] Technical area

[0004] The invention relates to a catalyst for the aftertreatment of exhaust gases of an internal combustion engine, comprising a honeycomb body wound from at least one metal foil, wherein the honeycomb body has a central axis which extends along its axial extent from a gas inlet side of the honeycomb body to a gas outlet side of the honeycomb body, and the honeycomb body has a plurality of flow channels through which gas can flow from a gas inlet side of the honeycomb body to a gas outlet side.

[0005] State of the art

[0006] Metallic catalysts are installed in the exhaust system to convert pollutants from the exhaust gases emitted by combustion engines. To shorten the warm-up time of the installed catalysts, an electrically heated heating disk can be installed upstream of the catalyst. In catalysts with metallic honeycomb structures, this heating disk is held in place by so-called support pins, which are integrally bonded to the support catalyst on one side and to the heating disk on the other. The support pins serve both to mechanically fix the heating disk relative to the catalyst and to electrically insulate the heating disk from the catalyst.

[0007] Such catalysts, which are used as support catalysts for heating disks, are typically produced by stacking and winding a plurality of metal foils, with the metal foils being alternately smooth and textured. The honeycomb structure created by winding is inserted into a support shell, which gives the catalyst its final shape. The flow channels formed between the smooth and textured foils are straight and regularly run parallel to the central axis of the catalyst.

[0008] Alternatively, catalysts are known that do not have smooth foils. To still create flow channels in the honeycomb body through which gas can flow from a gas inlet side to a gas outlet side, the foils are structured in such a way that the resulting flow channels run at an angle to the central axis. This creates so-called cross-corrugations or herringbone structures.

[0009] By stacking structured films with opposite corrugation orientations, the structured films are prevented from slipping into each other.

[0010] A particular disadvantage of the prior art devices is that the aforementioned catalysts, which are constructed without a smooth layer, have inclined flow channels on both the gas inlet and outlet sides of the catalyst that do not run parallel to the central axis of the catalyst. The support pins described above cannot be used in such inclined channels. Another disadvantage is that the matrix of the honeycomb body forming the catalyst, the metal foils, can be easily damaged due to the small bending radii regularly used.

[0011] The use of a supporting catalyst with a smooth metal foil between the structured metal foils is disadvantageous because it increases the heat capacity of the honeycomb body. This, in turn, increases the heating time until the optimal operating temperature is reached. Furthermore, a honeycomb body with smooth metal foils is more costly to manufacture because it requires more material. Description of the invention, problem, solution, advantages

[0012] Therefore, it is the object of the present invention to provide a catalyst for exhaust gas aftertreatment which has a design optimized with regard to the metal foils used and, in particular, does not require the use of smooth metal foils between the structured metal foils and has a higher flexibility of the honeycomb body in the axial and / or tangential direction.

[0013] The problem with regard to the catalyst is solved by a catalyst having the features of claim 1.

[0014] One embodiment of the invention relates to a catalyst for the aftertreatment of exhaust gases from an internal combustion engine, comprising a honeycomb body wound from at least one metal foil, wherein the honeycomb body has a central axis which extends along its axial extent from a gas inlet side of the honeycomb body to a gas outlet side of the honeycomb body, and the honeycomb body has a plurality of flow channels through which flow can pass from a gas inlet side of the honeycomb body to a gas outlet side, wherein the honeycomb body is divided into individual axial sections along its axial extent, along which the central axis runs, wherein the axial sections have flow channel sections which run at different angles to the central axis.

[0015] The axial sections describe regions along the axial extent of the honeycomb body. The totality of the axial sections forms the entire honeycomb body with its axial extent. The individual axial sections are created by specially shaped regions in the metal foils used. The honeycomb body is preferably produced from a single wound layer stack, so that all axial sections formed in the honeycomb body are formed by the same metal foils.

[0016] The plurality of flow channels formed between the metal foils run from the gas inlet side of the honeycomb body to the gas outlet side. According to the invention, the flow channels are characterized in that they can have different orientations relative to the central axis of the honeycomb body within the individual axial sections. The flow channels within an axial section can, for example, run parallel to the central axis, be angled at a positive angle to the central axis, or be angled at a negative angle to the central axis.

[0017] At the transitions between the individual axial sections, deflections of the respective flow direction in the individual flow channels take place.

[0018] By alternating between straight axial sections with flow channels running parallel to the central axis and axial sections with angled flow channels, the radius at the deflection points is increased, thus reducing the material stress caused by the corrugation process. This reduces the occurrence of damage to the metal foils during the manufacturing process.

[0019] The catalyst according to the invention comprises a honeycomb structure constructed without a smooth layer, which is typically used to separate the structured metal foils and prevent them from sliding into each other. This simplifies the construction of the honeycomb structure and requires less material.

[0020] Depending on the design, the orientation of the flow channels in the axial sections can be different, with flow channels aligned parallel to the central axis alternating with flow channels positioned at an angle to the central axis.

[0021] It is particularly advantageous if each flow channel has flow channel sections corresponding to the number of axial sections, each of which extends along one of the axial sections. The flow channels all run from the gas inlet side to the gas outlet side of the catalyst. Thus, each flow channel also runs through all axial sections of the catalyst. Since the honeycomb body is produced in the axial direction from only one layer stack and the metal foils are therefore not interrupted, each flow channel extends through the axial sections without being interrupted by the transitions between the axial sections. The aim is to enable the highest possible flow through the honeycomb body, which is why as few flow channels as possible should be blocked. For manufacturing reasons, it can happen that individual flow channels become deformed and thus blocked.However, these cases are minor side effects that do not fundamentally change the function and structure of the honeycomb body.

[0022] It is also advantageous if the flow channel sections of the axial section which begins at the gas inlet side of the honeycomb body run parallel to the central axis of the honeycomb body and / or the flow channel sections of the axial section which ends at the gas outlet side of the honeycomb body run parallel to the central axis.

[0023] This is particularly advantageous when an upstream or downstream element needs to be fixed relative to the catalyst. In particular, a heating disk, which is fixed with straight support pins inserted into the flow channels and permanently connected to them, can be positioned particularly easily relative to the catalyst.

[0024] A preferred embodiment is characterized in that the flow direction of the respective flow channel sections is different relative to the central axis in directly adjacent axial sections.

[0025] The flow channels preferably have angles to the central axis of between 1 and 15 degrees, particularly preferably between 1 and 10 degrees. A catalyst according to the invention preferably has a cell density of 600 cpsi to 1200 cpsi (cells per square inch).

[0026] It is also preferable for the axial sections to be between 5 mm and 50 mm long along the central axis. The length of the axial sections is preferably between 5 mm and 50 mm. Axial sections with straight flow channel sections running parallel to the central axis on the gas inlet side and / or the gas outlet side preferably have a length of 5 mm to 10 mm. The short length of these axial sections ensures that the solder penetrates well into the subsequent axial sections during the gluing and soldering processes, thus creating a strong bond between the metal foils during the subsequent soldering process.

[0027] Individual axial sections can additionally have a special corrugation, with the corrugation maximum or minimum being cut and a protrusion of the metal foil in the opposite direction of the respective corrugation. This allows exhaust gas to flow between adjacent flow channels. Furthermore, this can achieve improved conversion at the catalyst, as the protrusion improves the gas flow, particularly making it more turbulent. The protrusions are particularly advantageous in combination with a heating disk attached to the catalyst, as they enable a multi-point solder connection between the support pins and the catalyst.

[0028] The protrusions can optionally be arranged in axial sections with flow channels running parallel to the central axis and / or in axial sections with flow channels positioned at an angle to the central axis. The protrusions are particularly preferably arranged in the region of the gas inlet side, and the axial beginning of the protrusion is particularly preferably arranged in a range of 1 mm to 10 mm, particularly preferably in a range of 1 mm to 5 mm, after the gas inlet side.

[0029] Furthermore, it is advantageous if at least one metal foil has slits extending in the circumferential direction of the honeycomb body in at least one axial section. The slits are preferably introduced into the metal foils prior to the corrugating process. The slits significantly reduce the material stresses during the corrugating process and thus reduce the risk of damage to the metal foils.

[0030] Another positive side effect of the slots, which run circumferentially in the wound honeycomb body, is that the catalyst exhibits increased flexibility in both the axial and tangential directions, thus avoiding cell deformations that regularly occur due to thermal shock in a continuous, slot-free honeycomb body. The slots can be arranged axially in straight axial sections or, preferably, at deflection points or transition points between axial sections with uneven alignment of the flow channel sections.

[0031] Furthermore, it is advantageous if the axial section adjacent to the gas inlet side has flow channel sections that run parallel to the central axis, with support pins inserted into individual flow channels and permanently connected to the honeycomb body. This particularly facilitates the connection of a heating disk to the catalyst.

[0032] It is also advantageous if the honeycomb body has alternating axial sections with a flow direction parallel to the central axis and axial sections with a flow direction at an angle to the central axis along its axial extent. This deliberately increases the radius at the deflection points or the transitions between the axial sections, thereby reducing the load on the metal foils and thus also on the honeycomb body.

[0033] Furthermore, it is advantageous if the honeycomb body is formed from a plurality of stacked metal foils wound around at least one pivot point. Furthermore, it is expedient if the transition between two directly adjacent axial sections represents a deflection point for the flow direction of a flow channel. This ensures that the flow channels are not interrupted by the transitions between the axial sections.

[0034] Advantageous further developments of the present invention are described in the subclaims and in the following description of the figures.

[0035] Short description of the drawings

[0036] The invention is explained in detail below using exemplary embodiments with reference to the drawings. In the drawings:

[0037] Fig. 1 is a sectional view through a catalyst with a honeycomb body according to the invention,

[0038] Fig. 2 is a detailed view of a special shape of a corrugated film, wherein the corrugation has a region in the corrugation maximum that is turned out in the opposite direction,

[0039] Fig. 3 is a sectional view through a catalyst, showing a supporting catalyst to which a heating disc is attached on the gas inlet side by means of support pins,

[0040] Fig. 4 is a sectional view through a supporting catalyst and a heating disc, with an alternative design of the successive axial regions,

[0041] Fig. 5 is a sectional view through a catalyst, wherein the honeycomb body has circumferentially extending slots within individual axial sections, and Fig. 6 is a sectional view through a catalyst, wherein the honeycomb body has circumferentially extending slots at the transitions between adjacent axial sections.

[0042] Preferred embodiment of the invention

[0043] Figure 1 shows a catalytic converter 1, wherein the honeycomb body 2 is accommodated in a casing tube 3. The honeycomb body has several axial sections 4, 5 through which exhaust gas can flow from the gas inlet side 6 to the gas outlet side 7.

[0044] The exemplary embodiment shown in Figure 1 shows alternating axial sections 5 with flow channel sections set at an angle to the central axis and axial sections 6 with flow channel sections running parallel to the central axis. The axial sections 5 alternately have a positive angle of incidence to the central axis and a negative angle of incidence to the central axis, resulting in an up-and-down movement of the flow channels along the axial extent of the honeycomb body 2 in the sectional view of Figure 1.

[0045] Figure 2 shows a perspective view of a corrugated metal foil 8, wherein the upwardly projecting wave maxima have protrusions 9 that extend outward from the corrugation in the opposite direction. In the embodiment of Figure 2, the protruded regions 9 themselves have a lesser corrugation than the main corrugation.

[0046] Figure 3 shows an alternative embodiment of a honeycomb body 2. A heating slide 12 is positioned in front of the honeycomb body on the gas inlet side and is connected to the honeycomb body via support pins 11. The honeycomb body 5 has an axial section 4 on its gas inlet side and an axial section 4 on its gas outlet side, each with flow channel sections running parallel to the central axis. The remainder of the honeycomb body 2 is formed by axial sections 5, each of which has flow channel sections set at an angle.

[0047] It can be seen that the axial sections 4 on the gas inlet side and the gas outlet side each have a significantly shorter axial extension than the middle axial sections 5.

[0048] Figure 4 shows a honeycomb body 2 with a heating disk 12 positioned upstream. The axial sections 4 and 5 are arranged alternately, so that starting with an axial section 4, an axial section 5 follows, and so on, until another axial section 4 follows on the gas outlet side. The flow channels thus created follow an up-and-down movement along the axial extent of the honeycomb body.

[0049] Figure 5 shows another alternative honeycomb body 2, wherein axial sections 5 and axial sections 4 are again arranged alternately. In contrast to the previous figures, the axial sections 4 now have additional slots 13 extending in the circumferential direction of the honeycomb body 2. The slots 13 are arranged centrally in the axial sections 4.

[0050] Figure 6 shows a honeycomb body 2 as in Figure 5. In contrast to Figure 5, the slots 13 are now arranged directly in the transitions between the axial regions 4 and 5.

[0051] The different features of the individual embodiments can also be combined with each other.

[0052] The embodiments of Figures 1 to 6 are not limiting in nature and serve to clarify the inventive concept. List of reference symbols

[0053] 1 . Catalyst

[0054] 2. Honeycomb body 3. Casing tube

[0055] 4. axial section

[0056] 5. axial section

[0057] 6. Gas inlet side

[0058] 7. Gas outlet side 8. Metal foil

[0059] 9. Protrusion

[0060] 11 . Support pins

[0061] 12. Heating disc

[0062] 13. Slots

Claims

Patent claims 1. Catalyst (1) for the aftertreatment of exhaust gases from an internal combustion engine, comprising a honeycomb body (2) wound from at least one metal foil, wherein the honeycomb body (2) has a central axis which extends along its axial extent from a gas inlet side (6) of the honeycomb body (2) to a gas outlet side (7) of the honeycomb body (2), and the honeycomb body (2) has a plurality of flow channels through which flow can pass from a gas inlet side (6) of the honeycomb body (2) to a gas outlet side (7), characterized in that the honeycomb body (2) is divided into individual axial sections (4, 5) along its axial extent, along which the central axis runs, wherein the axial sections (4, 5) have flow channel sections which run at different angles to the central axis.

2. Catalyst (1) according to claim 1, characterized in that each flow channel has flow channel sections corresponding to the number of axial sections (4, 5), which each extend along one of the axial sections (4, 5).

3. Catalyst (1) according to one of the preceding claims, characterized in that the flow channel sections of the axial section (4), which begins at the gas inlet side (6) of the honeycomb body (2), run parallel to the central axis of the honeycomb body (2) and / or the flow channel sections of the axial section (4), which ends at the gas outlet side (7) of the honeycomb body (2), run parallel to the central axis.

4. Catalyst (1) according to one of the preceding claims, characterized in that the flow direction of the respective flow channel sections relative to the central axis is different in directly adjacent axial sections (4, 5).

5. Catalyst (1) according to one of the preceding claims, characterized in that the length of the axial sections (4, 5) is between 5mm and 50mm along the central axis.

6. Catalyst (1) according to one of the preceding claims, characterized in that at least one metal foil has slits (13) running in the circumferential direction of the honeycomb body (2) in at least one axial section (4, 5).

7. Catalyst (1) according to one of the preceding claims, characterized in that the axial section (4) adjacent to the gas inlet side (6) has flow channel sections which run parallel to the central axis, wherein support pins (11) are inserted into individual flow channels and are permanently connected to the honeycomb body (2).

8. Catalyst (1) according to one of the preceding claims, characterized in that the honeycomb body (2) has, along its axial extent, alternating axial sections (4) with a flow direction running parallel to the central axis and axial sections (5) with a flow direction running at an angle to the central axis.

9. Catalyst (1) according to one of the preceding claims, characterized in that the honeycomb body (2) is formed from a plurality of metal foils stacked on top of one another, which are wound around at least one pivot point.

10. Catalyst (1) according to one of the preceding claims, characterized in that the transition between two directly adjacent axial sections (4, 5) each represents a deflection point for the flow direction of a flow channel.

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