Device for an exhaust gas aftertreatment, and method for producing same

Abstract

The invention relates to a device for cleaning exhaust gases of an internal combustion engine, comprising a heating plate (7) which is made of a metal honeycomb body, said heating plate (7) being made of a plurality of metal foils which are stacked one on top of the other and are wound about at least one rotational axis. The heating plate (7) has air gaps (8) between the winding layers, said air gaps spacing the winding layers from one another and delimiting a flow path along the heating plate (7), wherein the honeycomb body has a plurality of flow channels, through which the exhaust gas can flow, and the heating plate (7) has a plurality of support elements (2), said support elements (2) of the heating plate (7) being inserted into the air gaps (8) formed between the winding layers.

Description

[0001] Description

[0002] Exhaust gas aftertreatment device and method for producing

[0003] Technical area

[0004] The invention relates to a device for purifying exhaust gases from an internal combustion engine, comprising a heating disk formed from a metallic honeycomb body. The heating disk is formed from a plurality of stacked metal foils wound around at least one rotational axis. The heating disk has air gaps between the winding layers, which space the winding layers apart and define a current path along the heating disk. The honeycomb body has a plurality of flow channels through which the exhaust gas can flow. The heating disk has a plurality of support elements. Furthermore, the invention relates to a method for producing the device.

[0005] State of the art

[0006] The prior art uses support pins to connect electric heating disks, which are formed as metallic honeycombs, to other honeycombs of so-called supporting catalysts. These pins are inserted into the cells of the respective honeycomb bodies and permanently connected to them by soldering. The support pins provide both the spatial fixation of the heating disk relative to the supporting catalyst and the electrical decoupling between the two honeycombs.

[0007] The permanent connection between the honeycomb bodies and the support pins is preferably made between their metallic sleeves or their metallic cores and the corrugated metal foils of the respective honeycomb body.

[0008] Depending on the design of the heating disc, more or fewer support pins are provided, which may also be arranged in multiple rows. The support pins are arranged in such a way, particularly with regard to thermal and mechanical stresses, that the highest possible durability during operation can be expected.

[0009] A particular disadvantage of the prior art devices is that a large number of support pins are required, which leads to high manufacturing costs. Another disadvantage of the previously known heating disks made of metallic honeycomb bodies is that, due to the electrical insulation of the individual layer stacks, an air gap must be formed between the individual layers. This renders the honeycomb bodies unstable and particularly susceptible to the occurrence of harmful vibration phenomena due to low natural frequencies. Furthermore, the air gap represents a type of bypass through which exhaust gas can unintentionally flow past the heating disk.

[0010] In addition, to ensure a good fit between the support pin and the corrugated layer of the honeycomb body, the corrugated layer must be specifically adapted with regard to its cell density and contour, as otherwise defects and non-bonding may occur during the soldering process, which would negatively affect the structural integrity.

[0011] Furthermore, the support pins lead to a blockage of the respective cell into which they are inserted, whereby these cells or flow channels are no longer available for exhaust gas aftertreatment.

[0012] Description of the invention, task, solution, advantages

[0013] Therefore, it is the object of the present invention to provide a device with an electrically heatable heating disk, which has an optimized structure and can optionally be connected to an upstream or downstream supporting catalyst by means of suitable supporting elements.

[0014] The object with regard to the device is achieved by a device having the features of claim 1. An embodiment of the invention relates to a device for cleaning exhaust gases of an internal combustion engine, having a heating disk formed from a metallic honeycomb body, wherein the heating disk is formed from a plurality of metal foils stacked on top of one another and wound around at least one axis of rotation, wherein the heating disk has air gaps between the winding layers, which space the winding layers from one another and delimit a current path along the heating disk, wherein the honeycomb body has a plurality of flow channels through which the exhaust gas can flow, wherein the heating disk has a plurality of support elements, wherein the support elements of the heating disk are inserted into the air gaps formed between the winding layers.

[0015] By inserting the support elements into the air gaps formed between the individual winding layers, a connection is created between the individual winding layers, allowing the individual winding layers to support each other. This mutual support significantly increases the stability of a heating disc created in this way, thereby improving its durability, particularly with regard to mechanical loads on the heating disc, which can be generated by the vibration of the heating disc itself and / or the other components in an exhaust system. In particular, by inserting the support elements and connecting the winding layers to one another, the number of different bending frequencies of the heating disc is reduced.

[0016] By increasing the stability of the heating disc, a large number of commonly used support elements can be eliminated, since the number of connection points to a supporting catalyst supporting the heating disc can be drastically reduced.

[0017] Preferably, the support elements are inserted exclusively in the air gaps, which achieves several advantages. Firstly, the flow channels formed in the heating disc are not blocked by the support elements. The exhaust gas can therefore flow through all flow channels, which improves the actual purpose of the heating disc, namely heating the exhaust gas. Furthermore, the support elements no longer have to be adapted to the geometry of the formed flow channels. This reduces the variety of parts, which enables easier production. Furthermore, low-cell heating discs, such as those used in truck applications, with only 50 or 75 cells per square inch (cpsi), can be positioned with normal support elements, which would normally be too narrow for the cell sizes of the heating disc.

[0018] Furthermore, the air gap, which inevitably creates an unwanted bypass effect by allowing exhaust gas to flow through it, is at least partially blocked by the support elements. Furthermore, the positioning of the support elements according to the invention enables more homogeneous heating of the heating disc.

[0019] A preferred embodiment is characterized in that the support elements inserted into the air gaps are in contact with each of the two winding layers that delimit the air gap in the radial direction and are permanently connected to them. This not only creates a high level of stability for the heating disc, but also allows for a targeted influence on the formation of the current path that results for the current between the two electrical connections of the heating disc. By selecting a support element that has no electrical insulation, two winding layers can be brought into electrically conductive contact with one another, thereby widening the current path. This also makes it possible to specifically supply more current to one area of ​​the heating disc, for example to ensure improved heat distribution across the heating disc.Electrically conductive support elements form so-called discrete current bridges that influence the current flow.

[0020] By selecting support elements that have an electrically insulating effect, for example through a suitable coating or an electrically insulating layer, winding layers can be specifically electrically insulated from one another. It is also preferable if at least a first number of the support elements are formed by support pins, wherein the support pins have a pin-shaped core which is enclosed at the ends in an electrically insulating material, wherein the electrically insulating material has two regions with a metallic coating on its outer circumference, wherein the regions are not in electrically conductive contact with one another, wherein the support pins project beyond the heating disc in the axial direction of extension of the heating disc.

[0021] The first support elements are designed like conventional support pins. They are characterized by being inserted into the heating disc at one end, more precisely in the air gap of the heating disc, and connected to a support structure, for example, an upstream or downstream supporting catalyst, at their opposite end. Depending on the application, the support pins can be electrically insulated or electrically conductive. An insulating support pin usually has a metallic core, which is surrounded by an electrically insulating layer in the end regions. The insulating layer, usually a ceramic, has two unconnected regions provided with a metallic coating, via which a permanent connection to the structures of the heating disc or the supporting catalyst can be established.For this purpose, the ceramic can, for example, have an oval cross-section, with two areas, preferably located on opposite regions of the outer circumference of the ceramic, coated with a metallic layer. These metallized areas serve to connect the support element to the metal foils of the heating disc, for example, by soldering.

[0022] Furthermore, it is advantageous if the heating disc has a second number of support elements formed by spacers, wherein the spacers space adjacent winding layers apart from one another and do not protrude, or only protrude insignificantly, beyond the heating disc in the axial direction of extension of the heating disc.

[0023] In contrast to the first support elements, the second support elements do not have a metallic core extending beyond the heating disc. The second support elements do not serve to position the heating disc relative to another structure, but rather simply to fix the winding layers to each other. The second support elements, also called spacers, are inserted into the air gap and connected to the adjacent winding layers.

[0024] This increases the stability of the heating disc, ensures that the air gap is formed securely and, depending on the design of the spacer, creates a discrete current bridge between the winding layers or electrically insulates the winding layers from each other.

[0025] Furthermore, it is advantageous if the first support elements have an electrically insulating layer at one of their end regions, which electrically insulates the core from the honeycomb body into which the respective end region is inserted. The electrically insulating layer can be formed, for example, from a ceramic material.

[0026] It is also preferable if the first support elements have an end region with an oval cross-section, wherein the end region is formed by the metallic core, the ceramic insulation layer, and two metallically coated regions of the insulation layer, wherein the metallically coated regions are not in electrically conductive contact with one another. The cross-sectional shape of the support elements can be freely selected, as it no longer has to be designed depending on the respective geometry of the flow channels of the honeycomb body. However, an oval cross-section is particularly advantageous for positioning in the air gap in order to create a sufficiently large contact area between the winding layers and the support element. In addition, support elements with an oval cross-section have a high level of strength.

[0027] It is also expedient if the heating disc is fixed relative to a honeycomb body serving as a supporting catalyst by means of the first support elements, wherein the heating disc is fixed to the honeycomb body of the supporting catalyst by means of the sections of the support pins projecting beyond the heating disc. The end regions of the support elements facing the supporting catalyst are inserted into individual flow channels of the supporting catalyst, which is why the support elements in this region are preferably adapted to the cell geometry of the supporting catalyst.

[0028] Furthermore, it is advantageous if the first support elements engage on one side in the air gap of the heating disc formed between the winding layers and engage with the other side in a flow channel of the honeycomb body of the supporting catalyst.

[0029] The problem with regard to the method is solved by a method having the features of claim 7.

[0030] An embodiment of the invention relates to a method for producing a device according to one of the preceding claims, wherein the following method steps are carried out: a. Stacking metal foils on top of one another to form a layer stack b. Placing the layer stack produced on a rotatably mounted spiral plate which has means for positioning and / or fixing the layer stack formed from the metal foils, c. Inserting at least one support element into a recess provided for this purpose in the spiral plate, d. Winding up the layer stack by rotating the spiral plate about at least one axis of rotation e. Soldering the wound layer stack and the at least one inserted support element, wherein the insertion of the at least one support element can take place before or after the winding up of the layer stack.

[0031] Heating discs are preferably wound using a rotating plate or spiral plate. The layer stacks formed from the metal foils are twisted into a matrix applied to the spiral plate. The matrix, which is formed from wall sections, forms the future air gaps when twisted. The spiral plate preferably has a plurality of receptacles, into each of which a support element can be inserted. The receptacles are distributed over the spiral plate in such a way that an advantageous positioning of the support elements is achieved for the respective heating disc. The receptacles are arranged in the region of the wall sections of the spiral plate that form the air gaps to ensure that the support elements are positioned in the air gaps in the finished heating disc.

[0032] It is particularly advantageous if the spiral plate has at least one elevation which serves as a means for positioning the layer stack, wherein the recess for the at least one support element is arranged in the elevation.

[0033] It is also advantageous if the spiral plate has wall elements projecting vertically from a base plate, which occupy the spaces that form the air gaps in the finished heating disc. The shape and structure of the heating disc can be easily influenced by the positioning and shape of the wall elements.

[0034] It is also expedient if both first support elements formed by support pins and second support elements formed by spacers are used as support elements.

[0035] Advantageous further developments of the present invention are described in the subclaims and in the following description of the figures.

[0036] Short description of the drawings

[0037] The invention is explained in detail below using exemplary embodiments with reference to the drawings. In the drawings:

[0038] Fig. 1 is a perspective view of a spiral plate with support elements inserted into the recesses, Fig. 2 is a perspective view according to Figure 1, wherein a corresponding layer stack is screwed into the spiral plate, wherein it can be seen that the support elements are arranged in the area of ​​the air gaps,

[0039] Fig. 3 is a sectional view through the spiral plate according to Figure 1, and

[0040] Fig. 4 is a plan view of two heating discs, the left heating disc showing the prior art and the right heating disc showing a heating disc according to the invention with support elements in the air gap of the heating disc.

[0041] Preferred embodiment of the invention

[0042] Figure 1 shows a spiral plate 1 having a plurality of support elements 2 inserted into receptacles. In the exemplary embodiment of Figure 1, the receptacles are arranged such that the support elements 2 are arranged in rows. This is merely an example. Preferably, the support elements 2 are not distributed in rows across the spiral plate 1, but rather are arranged according to the load profile in such a way that a stable heating disk is produced and, at the same time, a suitable connection to a supporting catalyst (not shown) can be created.

[0043] The support elements 2 are, on the one hand, support pins 3 and, on the other hand, spacers 4. In contrast to Figure 1, support pins 3 and spacers 4 can also be arranged alternately.

[0044] The wall sections 5 serve to shape the layer stack (not shown), which is screwed into the spiral plate 1.

[0045] Figure 2 shows a spiral plate 1 according to Figure 1. The layer stack 6 is twisted between the wall sections 5, which deforms the layer stack and creates the basic shape of the heating disc. A soldering process following the winding process connects the support elements 2 to the layer stack 6, thus fixing the shape of the heating disc.

[0046] Figure 3 shows a section through a spiral plate 1. It can be seen that the receptacles for the support elements are formed by depressions in the spiral plate 1 and by cutouts in the wall sections 5. This means that the support elements 2 can be easily inserted into the spiral plate and fixed in position by the wall sections 5. Furthermore, it can be seen that the cutouts in the wall sections 5 ensure that the support elements 2 come into contact on both sides with the layer stack screwed into the spiral plate 1, thus creating a secure connection between the support elements 2 and the layer stack.

[0047] Figure 4 shows on the left side a plan view of the front side of a conventional heating disc, with the support elements inserted into the flow channels of the heating disc and connected there to the heating disc.

[0048] In contrast, Figure 4 shows on the right side a plan view of an end face of a heating disc 7 according to the invention, wherein the support elements 2 are arranged exclusively in the air gap 8 of the heating disc 7 and are connected to the metal foils of the heating disc 7 adjacent to the air gap 8.

[0049] The embodiments of Figures 1 to 4 are in particular not restrictive in nature and serve to clarify the inventive concept.

[0050] List of reference symbols

[0051] 1. Spiral plate

[0052] 2. Support elements 3. Support pin

[0053] 4. Spacers

[0054] 5. Wall section

[0055] 6. Layer stack

[0056] 7. Heating disc 8. Air gap

Claims

Patent claims 1. Device for cleaning exhaust gases from an internal combustion engine, with a heating disk (7) formed from a metallic honeycomb body, wherein the heating disk (7) is formed from a plurality of metal foils stacked on top of one another and wound around at least one axis of rotation, wherein the heating disk (7) has air gaps (8) between the winding layers, which space the winding layers apart and delimit a current path along the heating disk (7), wherein the honeycomb body has a plurality of flow channels through which the exhaust gas can flow, wherein the heating disk (7) has a plurality of support elements (2), characterized in that the support elements (2) of the heating disk (7) are inserted into the air gaps (8) formed between the winding layers.

2. Device according to claim 1, characterized in that the support elements (2) inserted into the air gaps are in contact with both winding layers delimiting the air gap in the radial direction and are permanently connected to them.

3. Device according to one of the preceding claims, characterized in that at least a first number of the support elements (2) are formed by support pins (3), wherein the support pins (3) have a pin-shaped core which is enclosed at the end in an electrically insulating material, wherein the electrically insulating material has two regions with a metallic coating on its outer circumference, wherein the regions are not in electrically conductive contact with one another, wherein the support pins (3) project beyond the heating disc in the axial direction of extension of the heating disc.

4. Device according to one of the preceding claims, characterized in that the heating disc (7) has a second number of support elements (2) formed by spacers (4), wherein the spacers (4) adjacent winding layers are spaced apart from one another and do not protrude or only protrude insignificantly beyond the heating disc (7) in the axial direction of extension of the heating disc.

5. Device according to one of the preceding claims, characterized in that the first support elements (3) have an electrically insulating layer at one of their end regions, which electrically insulates the core from the honeycomb body into which the respective end region is inserted.

6. Device according to one of the preceding claims, characterized in that the heating disc (7) is fixed by means of the first support elements (3) relative to a honeycomb body serving as a supporting catalyst, wherein the heating disc (7) is fixed to the honeycomb body of the supporting catalyst by means of the sections of the supporting pins (3) projecting beyond the heating disc (7).

7. Device according to claim 6, characterized in that the first support elements (3) engage on one side in the air gap (8) of the heating disc (7) formed between the winding layers and engage with the other side in a flow channel of the honeycomb body of the supporting catalyst.

8. A method for producing a device according to one of the preceding claims, characterized in that the following method steps are carried out: a. Stacking metal foils on top of each other to form a layer stack (6) b. Placing the layer stack (6) produced on a rotatably mounted spiral plate (1) which has means for positioning and / or fixing the layer stack (6) formed from the metal foils c. Inserting at least one support element (2) into a recess provided for this purpose in the spiral plate d. Winding up the layer stack (2) by rotating the spiral plate (1) about at least one axis of rotation e. Soldering the wound layer stack (6) and the at least one inserted support element (2), wherein the insertion of the at least one support element (2) can take place before or after the winding up of the layer stack (6). Method according to claim 8, characterized in that the spiral plate (1) has at least one elevation (5) which serves as a means for positioning the layer stack (6), wherein the recess for the at least one support element (2) is arranged in the elevation. Method according to one of the preceding claims 8 or 9, characterized in that the spiral plate (1) has wall elements (5) which project vertically from a base plate and occupy the spaces forming the air gaps in the finished heating disk.Method according to one of the preceding claims 8 to 10, characterized in that both first support elements formed by support pins (3) and second support elements (2) formed by spacers (4) are used as support elements (2).

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