Device for heating exhaust gas which can flow in an exhaust gas line

Abstract

The invention relates to a device for heating an exhaust gas flow of an exhaust gas source, in particular of an internal combustion engine, wherein the exhaust gas flow can flow within an exhaust gas line and the device for heating it is arranged within said exhaust gas line, wherein the device has a heating disc (8, 11, 12, 14) which is formed by a honeycomb body formed from a plurality of foils (1, 2, 9, 10, 15, 16), wherein at least a number of first foils (9, 10) are metallic and are structured at least in sections, wherein the foils (1, 2, 9, 10, 15, 16) are stacked on one another to form a layer stack and are wound about at least one rotational axis to form the honeycomb body, wherein the heating disc (8, 11, 12, 14) formed by the honeycomb body configures at least one defined electric line path along the first foils (9, 10) which can be electrically contacted by means of at least one electrical contacting means, wherein at least one of the foils is formed by a multi-layer foil (1, 2, 15, 16), wherein the multi-layer foil (1, 2, 15, 16) has alternating metallic (3, 6, 7) and ceramic layers (4, 5).

Description

[0001] Description

[0002] Device for heating exhaust gas flowing in an exhaust pipe

[0003] Technical area

[0004] The invention relates to a device for heating an exhaust gas flow of an exhaust gas source, in particular of an internal combustion engine, wherein the exhaust gas flow can flow within an exhaust line and the device for heating is arranged within this exhaust line, wherein the device has a heating disk which is formed by a honeycomb body formed from a plurality of films, wherein at least a number of first films are metallic and are structured at least in sections, wherein the films are stacked on top of one another to form a layer stack and are wound around at least one axis of rotation to form the honeycomb body, wherein the heating disk formed by the honeycomb body forms at least one defined electrical conduction path along the first films, which can be electrically contacted by means of at least one electrical contact.

[0005] State of the art

[0006] Electric heaters are used today to heat exhaust gas streams in the exhaust systems of internal combustion engines in order to raise the exhaust gas temperature to a specified minimum value as quickly as possible. Reaching a system-dependent minimum temperature is necessary to ensure the correct functioning of the catalysts provided for exhaust gas aftertreatment. Depending on the design, the complete chemical conversion of the exhaust gas at the catalyst only takes place above a so-called light-off temperature. This light-off temperature must be reached particularly quickly, especially after a cold start, to ensure that the exhaust gas is converted in accordance with legal requirements for exhaust gas aftertreatment. One design of such electric heaters known in the prior art is a heating disc formed from a honeycomb body. The heating disc is preferably formed from a stack of layers wound together to form a honeycomb body.To create a clear current path, the individual layers of the heating disc are spaced apart by air gaps. These air gaps are usually a few millimeters wide to prevent accidental contact between the layers, even during operation.

[0007] A particular disadvantage of the prior art devices is that the manufacture and creation of these air gaps is very complex and laborious, especially for honeycomb bodies with larger diameters. Furthermore, the air gaps represent a kind of flow bypass for the exhaust gas. Therefore, a certain portion of the exhaust gas always flows past the heated structure of the heating disc, which results in suboptimal heating. Furthermore, the conversion of the exhaust gas at the heating disc itself, which acts as a catalyst, is reduced.

[0008] Another disadvantage of the air gaps formed in the heating disc is the fact that they reduce the stability of the heating disc and are therefore particularly susceptible to natural vibrations, which can lead to contact between the layers or even to the destruction of the heating disc. To prevent this, a large number of support pins are used to brace the heating disc against a support structure, such as an upstream or downstream catalyst. These support pins significantly increase system costs and are an additional source of failure. Furthermore, vibrations can be transmitted from the support structure to the heating disc via the support pins, which can damage the heating disc or cause a short circuit.

[0009] Description of the invention, task, solution, advantages

[0010] Therefore, the object of the present invention is to create a heating disk for heating an exhaust gas stream that has no open air gaps, thus eliminating the known weaknesses of previously known heating disks. In particular, the aim is to reduce manufacturing costs, increase the natural frequency of the heating disk, improve exhaust gas conversion due to the absence of a flow bypass, and simplify production.

[0011] The problem with regard to the heating disc is solved by a heating disc having the features of claim 1.

[0012] An embodiment of the invention relates to a device for heating an exhaust gas stream of an exhaust gas source, in particular of an internal combustion engine, wherein the exhaust gas stream can flow within an exhaust line and the heating device is arranged within this exhaust line, wherein the device has a heating disk which is formed by a honeycomb body formed from a plurality of films, wherein at least a number of first films are metallic and are structured at least in sections, wherein the films are stacked on top of one another to form a layer stack and are wound around at least one axis of rotation to form the honeycomb body, wherein the heating disk formed by the honeycomb body forms at least one defined electrical conduction path along the first films, which can be electrically contacted by means of at least one electrical contact, wherein at least one of the films is formed by a multilayer film,wherein the multilayer film has alternating metallic and ceramic layers.

[0013] The foils of the honeycomb body can preferably be completely smooth, partially structured, or fully structured. In particular, the structured sections can have corrugations of varying amplitude and corrugation frequency. Thus, corrugated foils with a high corrugation height, known as macrostructures, can be used, while corrugated foils with comparatively lower corrugation heights, known as microstructures, can be used.

[0014] Stacking smooth or microstructured films and macrostructured films creates a honeycomb pattern, with flow channels being formed between the adjacent films. Winding the stack of layers creates a honeycomb body with two essentially smooth end faces. The flow channels run from one end face to the other and allow flow along a main flow direction.

[0015] The individual foils of the honeycomb body are preferably permanently bonded together after winding and, if necessary, after insertion into a casing, for example, by soldering. For this purpose, a solder material is applied using suitable processes, which are melted in a soldering furnace, thus creating a permanently durable bond.

[0016] A multilayer film is characterized by being formed from a plurality of layers. In the case according to the invention, the multilayer film preferably has five layers. A metallic layer, for example a metal foil or a fabric, is arranged centrally. This layer is coated on both sides with a ceramic layer. The ceramic layer serves to electrically insulate the adjacent metallic layers.

[0017] The ceramic layers are followed by metallic layers on both sides. These then form the visible outer surfaces of the multilayer film. The metallic outer layer is particularly advantageous because it allows for bonding to neighboring films of the honeycomb structure. The multilayer film can be easily bonded to the purely metallic films using the same process as the other films.

[0018] The central metallic layer provides the multilayer film with the necessary stability, while the multilayer film is preferably designed to be flexible enough to accommodate very small bending radii, preferably approximately 1 mm. The ceramic layers ensure electrical insulation, effectively preventing unwanted electrical conduction across the multilayer film.

[0019] The outer metallic layers represent the contact layers, through which the multilayer film can be bonded to the remaining films. In the simplest case, the multilayer film can be formed from just three layers, with a central ceramic layer followed by a metallic layer. Alternative designs can, for example, also have seven or nine layers, as long as the basic concept of at least one ceramic layer in the center and one metallic layer each as outer layers is maintained.

[0020] The stack of layers consisting of the metallic foils and the multilayer foil can be easily wound into a honeycomb structure. The multilayer foil ensures that the honeycomb structure has electrically insulated layers, forming a current path running from an inlet point to an outlet point. The otherwise usual air gap in the heating disc is eliminated and is no longer necessary thanks to the use of the multilayer foil.

[0021] It is particularly advantageous if the multilayer film has five individual layers, wherein the multilayer film has a metallic core which is covered on both sides with a ceramic layer, wherein a further metallic layer is connected to the ceramic layer.

[0022] Five layers are advantageous because they provide a central metallic layer to create the stability of the multilayer film. Two ceramic layers on either side provide electrical insulation, and two metallic layers on either side bond the multilayer film to the remaining films in the stack.

[0023] It is also advantageous if the multilayer film is smooth and arranged between two adjacent, at least partially structured first films. The multilayer film can function as a smooth film and, in particular, can be arranged between two at least partially structured films. It is also possible for a macrostructured film to be arranged on one side and a microstructured film to be arranged on the other side. A preferred exemplary embodiment is characterized in that the multilayer film is at least partially structured, in particular corrugated, and is arranged between two smooth first films. The multilayer film has technical properties that also allow it to be corrugated and to form a microstructure or a macrostructure. The multilayer film can thus be arranged in the layer stack instead of any other film used.

[0024] It is also preferable if the layer stack comprises two multilayer films which are spaced from each other by at least one first metallic film.

[0025] A plurality of multilayer films is particularly advantageous, as this doubles the insulation effect. The two multilayer films can be arranged in a stack, spaced apart from each other, for example, by a structured film. It is also possible to create multiple independent electrical conductor paths by using multiple multilayer films.

[0026] Furthermore, it is advantageous if the multilayer foil is permanently bonded to the directly adjacent first foils in the honeycomb body at its metallic layers forming the outer sides. In particular, the permanently bonded connection should be created using a soldering process, as this allows the metallic foils to be bonded to one another and the multilayer foil to the metallic foils to be bonded in a single operation.

[0027] Furthermore, it is advantageous if the device additionally comprises a supporting catalyst formed by a honeycomb body, against which the heating disk is supported, wherein the supporting catalyst is formed by stacking and winding a plurality of films, wherein the supporting catalyst comprises at least one multilayer film which projects beyond one of the end faces of the supporting catalyst along the main flow direction.

[0028] In order to advantageously position the heating disc in the exhaust pipe and in particular to prevent electrical contact with other elements, the heating disc can preferably be supported in an electrically insulated manner relative to a support structure, such as another honeycomb body.

[0029] According to the invention, the honeycomb body serving as a supporting catalyst can have at least one multilayer foil which, however, in contrast to the remaining metallic foils, has a longer extension along the main flow direction of the honeycomb body and thus projects beyond the end face delimiting the flow channels at least on one side.

[0030] This protruding multilayer foil is then preferably part of the layer stack that forms the heating disk. If the supporting catalyst and the heating disk have an identical or at least very similar structure, particularly with regard to the number of layers and winding type, both honeycomb bodies can be wound and subsequently soldered in a single operation.

[0031] The multilayer film thus assumes the support function from the heating disc to the supporting catalyst and at the same time also the electrical insulation of the electrical conduction path of the heating disc itself and the electrical insulation of the heating disc from the supporting catalyst.

[0032] It is also advantageous if the multilayer foil extending beyond the end face of the supporting catalyst is also part of the layer stack of the honeycomb body forming the heating disk. This ensures that the heating disk and supporting catalyst are firmly connected to each other and suitably electrically insulated from each other.

[0033] Furthermore, it is advantageous if the heating disc is fixed and spaced from the supporting catalyst by means of the multilayer foil projecting beyond the supporting catalyst.

[0034] Furthermore, it is advantageous if the multilayer film of the supporting catalyst comprises five layers, with the middle layer being a metallic layer having a ceramic layer on each side, with each of the ceramic layers being followed by a metallic layer. Advantageous further developments of the present invention are described in the dependent claims 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 multilayer film according to the invention, the multilayer film being shown once as a smooth film and once as a structured film,

[0038] Fig. 2 a view of a layer stack with two multilayer films,

[0039] Fig. 3 a view of a layer stack with a corrugated multilayer film,

[0040] Fig. 4 a view of a layer stack with a smooth multilayer film, and

[0041] Fig. 5 is a sectional view through a supporting catalyst with multilayer foils projecting along the flow direction, wherein a heating disk is also shown at a distance from the supporting catalyst.

[0042] Preferred embodiment of the invention

[0043] Figure 1 shows a multilayer film 1 consisting of five layers in the upper region. The multilayer film 1 is smooth in the upper region of Figure 1. The lower region of Figure 1 shows a multilayer film 2 that is structured, in particular corrugated. Both multilayer films 1, 2 have five layers, with the central layer 3 being metallic and the two adjacent layers 4, 5 being ceramic. The outer layers 6, 7 are also metallic.

[0044] Figure 2 shows a sectional view through a heating disk 8, wherein the heating disk 8 is formed from several metallic foils 9, 10. Two multilayer foils 1 are arranged within the heating disk, wherein the outer layers 6, 7 of the multilayer foil 1 are in contact with the adjacent metallic foils 9, 10 and are permanently bonded to one another.

[0045] The two multilayer films 1 are spaced apart by a corrugated metallic film 9. The heating disk shown in Figure 2 is constructed from coarsely structured (macrostructured) films 9 and finely structured (microstructured) films 10.

[0046] Figure 3 shows a section through an alternative heating disk 11, wherein the heating disk 11 is also formed from macrostructured films 9 and microstructured films 10. The heating disk 11 has a multilayer film 2 arranged between two microstructured films 10.

[0047] Figure 4 shows another alternative heating disk 12, wherein the heating disk 12 is also formed from macrostructured films 9 and microstructured films 10. The heating disk 12 has a multilayer film 1 arranged between two microstructured films 10.

[0048] Figure 5 shows a section through a supporting catalyst 13 formed from a wound stack of layers. Above the supporting catalyst 13, a heating disk 14 is shown, which is also formed from a wound stack of layers.

[0049] In the left part of Figure 5, the supporting catalyst 13 has a corrugated multilayer foil

[0050] 15, which protrudes beyond the upper end face of the supporting catalyst 13. In the right-hand part, the supporting catalyst 13 has a smooth multilayer film 16, which also protrudes beyond the upper end face. The supporting catalyst shown in Figure 5 is an example, and the different multilayer films 15, 16 are intended to illustrate that both smooth and corrugated multilayer films are possible. In a real design, the supporting catalyst 13 and the multilayer films protruding beyond the end face would be of uniform design across the entire cross-section. The two-part view in Figure 5 serves to illustrate the different design options.

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

[0052] The embodiments of Figures 1 to 5 are in particular not restrictive in nature and serve to clarify the inventive concept.

[0053] List of reference symbols

[0054] 1. Multilayer film smooth

[0055] 2. Multilayer film corrugated

[0056] 3. Central metal layer

[0057] 4. ceramic layer

[0058] 5. ceramic layer

[0059] 6. Metal layer

[0060] 7. Metal layer

[0061] 8. Heating disc

[0062] 9. Macrostructured film

[0063] 10. Microstructured film

[0064] 11 . Heating disc

[0065] 12. Heating disc

[0066] 13. Support catalyst

[0067] 14. Heating disc

[0068] 15. corrugated multilayer film

[0069] 16. smooth multilayer film

Claims

Patent claims 1. Device for heating an exhaust gas stream from an exhaust gas source, in particular an internal combustion engine, wherein the exhaust gas stream is flowable within an exhaust gas line and the device for heating is arranged within this exhaust gas line, wherein the device has a heating disc (8, 11, 12, 14) which is formed by a honeycomb body formed from a plurality of foils (1, 2, 9, 10, 15, 16), wherein at least a number of first foils (9, 10) are metallic and are structured at least sectionally, wherein the foils (1, 2, 9, 10, 15, 16) are stacked on top of each other to form a layer stack and are wound around at least one axis of rotation to form the honeycomb body, wherein the heating disk (8, 11, ) formed by the honeycomb body 12, 14) forms at least one defined electrical conduction path along the first foils (9, 10) which can be electrically contacted by means of at least one electrical contact, characterized in that at least one of the foils is formed by a multilayer foil (1, 2, 15, 16) wherein the multilayer foil (1, 2, 15, 16) has alternating metallic (3, 6, 7) and ceramic layers (4, 5).

2. Device according to claim 1, characterized in that the multilayer film (1, 2, 15, 16) has five individual layers (3, 4, 5, 6, 7), wherein the multilayer film (1, 2, 15, 16) has a metallic core (3) which is coated on both sides with a ceramic layer (4, 5), wherein a further metallic layer (6, 7) is attached to the ceramic layer (4, 5).

3. Device according to one of the preceding claims, characterized in that the multilayer film (1, 16) is smooth and is arranged between two adjacent at least partially structured first films (9, 10).

4. Device according to one of the preceding claims, characterized in that the multilayer film (2, 15) at least The multilayer film (1, 2, 15, 16) is partially structured, in particular corrugated, and is arranged between two smooth first films. A device according to one of the preceding claims, characterized in that the stack of layers comprises two multilayer films (1) which are spaced apart from each other by at least one first metallic film (9). A device according to one of the preceding claims, characterized in that the multilayer film (1, 2, 15, 16) is permanently bonded at its outer surfaces (7, 8) to the directly adjacent first films (9, 10) in the honeycomb structure.Device according to one of the preceding claims, wherein the device additionally comprises a support catalyst (13) formed by a honeycomb structure, against which the heating disc (14) is supported, characterized in that the support catalyst (13) is formed by stacking and winding several films, wherein the support catalyst (13) comprises at least one multilayer film (15, 16) which projects beyond one of the end faces of the support catalyst (13) along the main flow direction. Device according to claim 7, characterized in that the multilayer film (15, 16) projecting beyond the end face of the support catalyst (13) is also part of the layer stack of the honeycomb structure forming the heating disc (14).Device according to one of the preceding claims, characterized in that the heating disc (14) is fixed and spaced apart from the supporting catalyst (13) by means of the multilayer film (15, 16) projecting beyond the supporting catalyst (13). Device according to one of the preceding claims, characterized in that the multilayer film (15, 16) of the supporting catalyst (13) is... The catalyst has five layers, the middle layer being a metallic layer, which has a ceramic layer on both sides, with each ceramic layer being followed by a metallic layer.

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