DEVICE FOR LOW-VOID EXHAUST FUME TREATMENT

Description

Technical field

[0001] The invention relates to a device for the aftertreatment of exhaust gases from an internal combustion engine, comprising a honeycomb body through which flow is directed along a main flow direction, a ceramic mat, and at least one first jacket which receives the honeycomb body, wherein the ceramic mat is arranged between the honeycomb body and the jacket and surrounds the honeycomb body in a ring-like manner in the circumferential direction. The invention further relates to a method for manufacturing a device according to the invention, wherein the honeycomb body is received in a second jacket and the honeycomb body received in the second jacket is surrounded by the ceramic mat in a ring-like manner in the circumferential direction, wherein the second jacket has a section at the end region facing the gas inlet side which has a structure that differs from the rest of the structure of the second jacket. State of the art

[0002] Honeycomb bodies for catalysts used in the exhaust aftertreatment of combustion engines feature a plurality of flow channels through which flow can occur along a main flow direction. Honeycomb bodies, particularly those made of metal, are formed by a multitude of smooth and / or at least partially structured metal foils, which are stacked on top of each other and wound to form the final honeycomb structure. For stabilization and protection against mechanical damage, the matrix formed from the metal foils is inserted into a housing and permanently bonded to it.

[0003] In its simplest form, the housing is a tube designed to contain the matrix. Another function of the housing is to ensure airflow through the honeycomb structure and, in particular, to prevent exhaust gas from bypassing it.

[0004] The matrix must be permanently fixed within the housing, while the housing itself should be as lightweight as possible and therefore have thin walls. Some catalyst designs feature an inner shell that directly holds the matrix. This inner shell is then supported against the housing or outer shell by suitable supports.

[0005] US Patent 2003 / 0180198 A1 discloses a catalyst assembly comprising a housing with at least one first and one second recess with side surfaces, and a catalyst support body mounted in this housing. The catalyst support body has a jacket tube and a honeycomb core through which exhaust gas can flow. The jacket tube has at least one first and one second protrusion with side surfaces, and the jacket tube is connected to the honeycomb core, at least in a partial area. The projections extend at least partially into the recesses to form a fixed bearing and at least one floating bearing with axial play. This arrangement ensures the catalyst support body is permanently fixed, particularly in the presence of structure-borne vibrations occurring in the exhaust system of an internal combustion engine.

[0006] A particular disadvantage of the prior art devices is that air gaps can form between the individual elements of a catalyst, for example, between the inner and outer shells. These gaps can be filled by the catalytically active material used to coat the matrix. Mechanical vibrations and thermal influences during operation can dislodge this material trapped in the air gaps, potentially leading to damage and / or the catalytic deactivation of downstream exhaust aftertreatment components.Furthermore, a convective flow can occur in the space between the inner and outer jackets, provided this space is accessible to flowing exhaust gas, which significantly improves the heat transfer between the inner and outer jackets and thereby considerably reduces the desired thermal insulation effect, causing the catalyst to lose temperature and thus effectiveness. Description of the invention, problem, solution, advantages

[0007] Therefore, the object of the present invention is to provide a device for exhaust gas aftertreatment which enables the matrix to be securely contained within a housing and simultaneously reduces or completely avoids the formation of air gaps between the individual components in order to prevent the unintentional detachment of coating material. Furthermore, the invention relates to a method for manufacturing a device according to the invention.

[0008] The problem with regard to the device is solved by a device having the features of claim 1.

[0009] An embodiment of the invention relates to a device for the aftertreatment of exhaust gases from an internal combustion engine, comprising a honeycomb body through which flow is directed along a main flow direction, a ceramic mat, and at least one first jacket which receives the honeycomb body, wherein the ceramic mat is arranged between the honeycomb body and the jacket and surrounds the honeycomb body in a ring-like circumferential direction, wherein the ceramic mat is designed such that the cavity formed between the honeycomb body and the first jacket is completely filled by the ceramic mat, wherein the honeycomb body is received into a second jacket and the honeycomb body received into the second jacket is surrounded by the ceramic mat in a ring-like circumferential direction, wherein the second jacket has a section at the end region facing the gas inlet side which has a structure,which differs from the rest of the structure of the second jacket, wherein the second jacket has openings in this section which are spaced apart from each other in the circumferential direction on the gas inlet side.

[0010] The mat serves to fix the honeycomb core within the first casing, which typically forms the outer casing of the device. The ceramic mat is designed to have thermal insulation properties, thus significantly reducing heat loss to the outer casing. The mat is arranged circumferentially around the entire honeycomb core to ensure that no air gaps form between the honeycomb core and the outer casing. The ceramic mat is capable of absorbing mechanical stresses and, if necessary, partially relieving them through compression. These mechanical stresses can arise, in particular, from the expansion of the honeycomb core matrix under the influence of heat.

[0011] The ceramic mat preferably has a thickness of 2mm to 5mm and, in addition to the aforementioned strong thermal insulation, also has electrically insulating properties, which is particularly advantageous if the honeycomb body is electrically heated or if it is in conductive contact with an electrically heated honeycomb body.

[0012] This is particularly advantageous because a second coat can improve manufacturing.

[0013] The second layer, preferably an inner layer positioned between the honeycomb core and the ceramic mat, can be subjected to radial force and thus selectively expanded to a predetermined internal cross-section. This process is also called inner layer calibration. In this way, a certain prestress can be generated between the inner layer and the ceramic mat, while simultaneously creating an internal cross-section of the inner layer that is favorable for accommodating the honeycomb core.

[0014] The section at the gas inlet side is formed, in particular, by an annular region extending from the gas inlet side along the axial extent of the honeycomb structure. This section can differ from the rest of the second shell, for example, in the choice of material, the thickness of the material, or the porosity of the material. In particular, structures can be incorporated into this section that cause a change in the heat capacity.

[0015] Openings can be formed, for example, by rectangular windows spaced apart from one another. Alternatively, round or oval holes can be provided, arranged in a predefined pattern. For instance, the number or size of the holes can be specified to vary along the axial length.

[0016] It is also advantageous if the section of the second jacket on the gas inlet side is made of a material different from the rest of the second jacket, and this different material has a significantly reduced heat capacity. For example, expanded metal with openings in its structure can preferably be used. Alternatively, a material with a lower heat capacity can be selected.

[0017] Furthermore, it is preferable for the section of the second layer to have a porosity of 50% to 90% compared to the porosity of the rest of the second layer. This altered porosity reduces the thermal mass of the second layer, thereby promoting the heating of the catalytically active structure of the honeycomb body.

[0018] Furthermore, it is advantageous if the ceramic mat in the section on the gas inlet side is at least partially directly exposed to the fluid flowing in the honeycomb body.

[0019] Furthermore, it is preferable if the section of the second jacket has an axial extension of 20 mm to 50 mm when viewed from the gas inlet side. An extension over such an axial length has proven particularly advantageous in exhaust aftertreatment devices for passenger cars.

[0020] It is also advantageous if the second jacket is significantly thinner than the first jacket, preferably being 4 to 20 times thicker than the second jacket. This is advantageous because it reduces the thermal mass to a minimum.

[0021] Preferably, the first sheath, which forms the outer sheath of the device, has a thickness of 2 mm to 5 mm. This is necessary to ensure a gas-tight seal and sufficient mechanical stability. The second sheath, which forms the inner sheath between the honeycomb core and the ceramic mat, preferably has a thickness of 0.1 mm to 0.55 mm. The inner sheath should be particularly lightweight and expandable or calibrated with relatively little force, so that a suitable cross-section can be formed to accommodate the honeycomb core.

[0022] A preferred embodiment is characterized in that the first casing has a radially projecting section. Such a projecting area is advantageous because, viewed from the inside, it forms a radially outward-curving, circumferential pocket into which, in particular, the ceramic mat can be received to a large extent or even completely along its radial length. By limiting this projection in the axial direction, additional fixation of the ceramic mat and thus of the honeycomb structure can also be achieved.

[0023] It is also preferable if the radially extended area accommodates the ceramic mat. This is particularly advantageous for creating both radial fixation of the ceramic mat and axial fixation within the first or outer layer.

[0024] The problem with regard to the method is solved by a method having the features of claim 6.

[0025] One embodiment of the invention relates to a method for manufacturing a device according to the invention, wherein the honeycomb body is inserted into a ceramic mat, wherein the ceramic mat with the received honeycomb body is inserted into the first jacket, wherein at least a radially acting force is applied to the first jacket, the ceramic mat and / or the honeycomb body.

[0026] Applying a radially acting force can either expand or compress individual components. In either case, this results in increased contact between adjacent components.

[0027] Applying a radial force can be used for calibration. This involves expanding or compressing at least one of the components to a defined dimension. This allows, for example, differences in the cross-section of the individual components to be compensated for and a tight fit between them to be achieved.

[0028] Furthermore, it is advantageous if the device has a second jacket, wherein the second jacket has an outer diameter that is smaller than or equal to the inner diameter of the ceramic mat, wherein the second jacket expands radially after being inserted into the ceramic mat, thereby compressing the ceramic mat in a radial direction and / or generating a force acting radially from the ceramic mat onto the first jacket.

[0029] In a first arrangement, a ceramic mat is inserted into the first outer shell. The second inner shell is then inserted into the ceramic mat. The inner shell has a smaller outer diameter than the inner diameter of the ceramic mat. Subsequently, a radially outward force is applied to the inner shell from the inside, causing it to expand to a predefined dimension. This force also acts on the ceramic mat, compressing it. Depending on the design, a force component may also act on the outer shell.

[0030] The inner jacket, expanded to the required dimensions, can then accommodate the honeycomb core, which is subsequently soldered to the inner jacket. This expansion ensures a tight fit between the inner jacket, the ceramic mat, and the outer jacket, preventing any air gaps from forming between the individual components. This eliminates cavities that could be unintentionally filled with the coating material during the subsequent application of a catalytically active coating to the honeycomb core.

[0031] It is particularly advantageous that no coating material accumulates in cavities outside the honeycomb structure to prevent unwanted detachment of this coating material during subsequent operation. Since the coating material is catalytically active, it is chemically reactive, which can lead to damage to downstream exhaust aftertreatment components, especially when interacting with other coating materials. This is referred to as "poisoning," as the exhaust aftertreatment capability of the downstream components can be severely impaired.

[0032] Furthermore, it is advantageous if the honeycomb body, after winding, is fixed against fanning out by a plurality of welding points and inserted into a ceramic mat, wherein the ceramic mat has an inner diameter identical to the outer diameter of the fixed honeycomb body, wherein the ceramic mat with the honeycomb body is inserted into a first shell which has a larger inner diameter than the outer diameter of the ceramic mat, wherein after insertion of the ceramic mat a radial force is applied from the outside to the first shell, thereby reducing the diameter of the first shell.

[0033] An alternative approach involves fixing the coiled honeycomb core to the matrix, for example, with spot welds. This prevents the matrix from curling or fanning out. The honeycomb core is inserted into a ceramic mat precisely shaped to accommodate it. The assembly of honeycomb core and ceramic mat is then inserted into the outer casing, which has a larger inner diameter than the core. The outer casing can optionally have an outward-facing protrusion or be cylindrical.

[0034] A radially inward-directed force is then applied to the outer shell, which compresses the outer shell and thus causes the outer shell to be pressed against the ceramic mat.

[0035] It is also advantageous if the radial force is applied to the first shell in such a way that the ceramic mat within the first shell is compressed both radially and axially. This can be achieved particularly effectively if the outer shell has an outwardly projecting protrusion into which the ceramic mat and the honeycomb core are inserted. In particular, an outer shell with a projecting section allows for easy fixation even in the axial direction, as the ceramic mat comes into contact with the flanks of the outer shell extending from the projecting section to the non-projecting section.

[0036] Furthermore, it is advantageous if the radial force is applied to the radially elongated section of the first sheath. This is particularly advantageous because the ceramic mat with the honeycomb core is located in this section.

[0037] Advantageous embodiments of the present invention are described in the dependent claims and in the following description of the figures. Brief description of the drawings

[0038] The invention will now be explained in detail using exemplary embodiments and with reference to the drawings. The drawings show: Fig. 1 a schematic view with a honeycomb structure enclosed in an inner shell and a ceramic mat enclosed in an outer shell. Fig. 2 a schematic view corresponding to the Figure 1 , wherein the outer shell has a radially outwardly projecting section, Fig. 3 a schematic view according to the Figure 2, wherein no inner mantle is arranged between the ceramic mat and the honeycomb body, and Fig. 4 a perspective section view through a second mantle serving as an inner mantle, which in one section on the gas inlet side has a structure different from the rest of the second mantle. Preferred embodiment of the invention

[0039] The Figure 1 Figure 1 shows a device 1 for exhaust gas aftertreatment. The device 1 has a honeycomb body 2, which is received in an inner shell 3. The honeycomb body 2 with the inner shell 3 is received in a ceramic mat 4. The ceramic mat 4 is in turn received in the outer shell 5, which can form the externally visible housing.

[0040] The Figure 1Figure 2 shows a cross-sectional view through the central axis of the honeycomb body 2. The inner lining 3, the ceramic mat 4, and the outer lining 5 are all ring-shaped elements that enclose the cylindrical honeycomb body. In alternative configurations, cross-sectional shapes other than a circular cross-section can also be chosen.

[0041] To the left of the honeycomb body 2, a heating disc 6 of an electrically heated honeycomb body is shown, which is connected to the honeycomb body 2 via support pins 7. The heating disc 6 can be electrically connected via electrical feedthroughs 8, 9. By applying a current to the heating disc 6, it can be heated by utilizing its ohmic resistance. The heating disc 6 can be positioned upstream or downstream of the honeycomb body 2 in the direction of current flow.

[0042] The outer shell 5 of the Figure 1The structure is tubular in shape and has a cross-section that remains constant along its length. Preferably, the inner sheath 3 is subjected to a radially outward force to compress the ceramic mat 4 in the radial direction and exert pressure on the outer sheath 5. This allows the assembly, consisting of the honeycomb body 2, inner sheath 3, and ceramic mat 4, to be fixed relative to the outer sheath 5. Additionally, it is possible to subject the outer sheath 5 to a radially inward force after the honeycomb body 2 has been inserted, in order to compress the entire device and fix the individual components to one another. Alternatively or additionally, individual components or all components can be joined together by soldering or a similar process to create a material bond.

[0043] The Figure 2 shows one of the Figure 1similar structure. Identical elements are therefore marked with the same reference symbols. In contrast to the Figure 1 The outer shell 10 is designed such that it has a radially outwardly projecting section 11. This projection 11 is preferably fully circumferential and forms a receiving area 12 for the ceramic mat 4 inside the outer shell 10.

[0044] By applying a radially inward force to the outer shell 10, the ceramic mat 4 can be fixed inside. By arranging the ceramic mat 4 within the receiving area 12 formed by the protrusion 11, it is also additionally fixed in the axial direction of the device 1.

[0045] The Figure 3 shows an alternative design of the device Figure 2 Unlike the Figure 2 is in the Figure 3No inner sheath 3 is provided. In an embodiment according to Figure 3 The fully wound honeycomb body 2 is fixed against fanning out or rolling up by means of a plurality of welding points.

[0046] The honeycomb body 2 is then inserted into a ceramic mat 4 and placed into the receiving area 12 of the outer shell 10. By applying a radially inward-directed force, the honeycomb body 2 together with the ceramic mat 4 is fixed in the outer shell 10.

[0047] By applying the radial forces in the devices from the Figures 1 to 3 This ensures a tight fit, thus preventing air gaps from forming between the individual components. Coating the honeycomb structure with a catalytically active surface coating therefore prevents the deposition of coating material in air gaps.

[0048] Figure 4Figure 1 shows an inner shell 3, which has a section 22 extending from the gas inlet side 20 along the axial length designated by reference numeral B. The inner shell 3 is inserted into an outer shell 5, the outer shell 5 forming a cavity into which a ceramic mat 4 is inserted.

[0049] In the exemplary embodiment of the Figure 4 Section 2 has several rectangular openings 21. The openings are spaced apart from each other in the circumferential direction and thus drastically reduce the thermal mass of the second jacket 3 in section 22.

[0050] In the exemplary embodiment of the Figure 4In this exemplary embodiment of an object according to the invention, the rectangular openings 21 have a width C along the circumferential direction, which is preferably 30 mm. The axial extent of the openings 21 is 30 mm in this embodiment. The circumferential spacing D is 5 mm in this embodiment. The distance A between the edge bounding the second jacket 3 at the gas inlet side 20 and the openings 21 is preferably 7 mm. This example shown here has 10 openings.

[0051] Deviations from this are foreseeable. The exemplary embodiment of the Figure 4 shows one possible design.

[0052] The different features of the individual embodiments can also be combined with one another within the scope of the claims. In particular, the outer shell with protrusion can be combined with an inner shell.

[0053] The examples of implementation of Figures 1 to 4 In particular, they do not have a restrictive character and serve to clarify the inventive idea.

Claims

1. Device (1) for the aftertreatment of exhaust gases from an internal combustion engine, with a honeycomb body (2) through which a flow can pass along a main flow direction from a gas inlet side to a gas outlet side, with a ceramic mat (4) and with at least one first casing (5, 10) which receives the honeycomb body (2), wherein the ceramic mat (4) is arranged between the honeycomb body (2) and the casing (5, 10) and surrounds the honeycomb body (2) as a ring in the peripheral direction, wherein the ceramic mat (4) is configured such that the cavity formed between the honeycomb body (2) and the first casing (5, 10) is completely filled by the ceramic mat (4), wherein the honeycomb body (2) is received in a second casing (3) and the honeycomb body (2) received in the second casing (3) is surrounded by the ceramic mat (4) as a ring in the peripheral direction, wherein the second casing (3) has, at the end region facing the gas inlet side (20), a portion (22) having a structure which is different from the remaining structure of the second casing (3), characterized in that the second casing (3) has openings (21) in the portion (22) which are arranged spaced apart from one another in the peripheral direction on the gas inlet side (20).

2. Device (1) according to Claim 1, characterized in that the portion (22) of the second casing (3) on the gas inlet side (20) is made from a material different from that of the remaining second casing (3), wherein this different material has a significantly reduced thermal capacity.

3. Device (1) according to Claim 2, characterized in that the portion (22) of the second casing (3) has a porosity of 50% to 90%, in comparison with the porosity of the remaining second casing (3).

4. Device (1) according to any of the preceding claims, characterized in that the ceramic mat (4) in the portion (22) on the gas inlet side (20) is at least in portions directly exposed to the fluid flowing in the honeycomb body (2).

5. Device (1) according to any of the preceding claims, characterized in that the portion (22) of the second casing (3) has an axial extent of 20 mm to 50 mm, viewed from the gas inlet side (20).

6. Device (1) according to any of the preceding claims, characterized in that the second casing (3) is substantially thinner than the first casing (5, 10), wherein preferably the first casing (5, 10) is 4 to 20 times thicker than the second casing (3).

7. Device (1) according to any of the preceding claims, characterized in that the first casing (10) has a portion (11) which bulges outward in the radial direction.

8. Device (1) according to Claim 7, characterized in that the region (12) bulging outward in the radial direction receives the ceramic mat (4).

9. Method for producing a device (1) according to any of the preceding claims, characterized in that the honeycomb body (2) is inserted in a ceramic mat (4), wherein the ceramic mat (4) with the received honeycomb body (2) is inserted in the first casing (5, 10), wherein at least a radially acting force is exerted on the first casing (5, 10), the ceramic mat (4) and / or the honeycomb body (2).

10. Method for producing a device (1) according to Claim 9, characterized in that the device (1) has a second casing (3), wherein the second casing (3) has an outer diameter which is smaller than or equal to the inner diameter of the ceramic mat (4), wherein the second casing (3) is radially widened after insertion in the ceramic mat (4), whereby the ceramic mat (4) is compressed in the radial direction and / or a force acting in the radial direction is exerted by the ceramic mat (4) on the first casing (5, 10).

11. Method according to Claim 9, characterized in that the honeycomb body (2), after winding, is fixed against fanning out by a plurality of weld points and inserted in a ceramic mat (4), wherein the ceramic mat (4) has an inner diameter identical to the outer diameter of the fixed honeycomb body (2), wherein the ceramic mat (4) with the honeycomb body (2) is inserted in a first casing (5, 10) which has a greater inner diameter than the outer diameter of the ceramic mat (4), wherein after insertion of the ceramic mat (4), a radial force is exerted from the outside onto the first casing (5, 10), whereby the diameter of the first casing (5, 10) is reduced.

12. Method according to Claim 11, characterized in that the radial force is exerted on the first casing (5, 10) such that the ceramic mat (4) in the first casing (5, 10) is compressed in both the radial direction and also in the axial direction.

13. Method according to Claim 12, characterized in that the radial force is exerted on the portion (11) of the first casing (10) which bulges outward in the radial direction.