DEVICE FOR HEATING AN EXHAUST FUME

Description

Technical area

[0001] The invention relates to a device for heating an exhaust gas flow of an exhaust gas source, comprising a honeycomb body through which flow occurs along a main flow direction, which honeycomb body is produced from a plurality of metallic foils by stacking and winding them up, wherein the honeycomb body has at least one electrical conduction path which can be electrically contacted by means of at least one electrical contact. State of the art

[0002] Different catalysts are used for exhaust gas aftertreatment. Depending on the application, these catalysts are formed, for example, by ceramic substrates coated with different coatings that chemically react with individual components of the exhaust gas, producing less harmful substances. Alternatively, metallic honeycomb structures are known.

[0003] All catalytic converters have in common that, for optimal performance, they must reach a certain minimum temperature so that the chemical reactions can take place. Particularly in light of increasingly stringent emissions standards, these minimum temperatures must be reached ever earlier, necessitating the provision of active heating measures in addition to the thermal energy from the exhaust gases. This is particularly relevant with regard to hybrid vehicles, as these are increasingly operated purely electrically, at least in phases, and thus cold-start processes of the combustion engine, during which the components in the exhaust system may also cool below their operating temperature, occur more frequently.

[0004] One known prior art technique is the use of electrically heated catalysts, which utilize electrical resistance to generate heat and thus directly heat the catalytic substrate and the catalytically active coating. For this purpose, electrical conductors are subjected to a current, which heats the electrical conductor.

[0005] The electrically heated honeycomb bodies must, on the one hand, be positioned in a fixed position in the exhaust gas tract and, on the other hand, be electrically insulated from other electrically conductive components.

[0006] It is known in the prior art that electrically heated honeycomb bodies are attached to another catalyst arranged in the exhaust system by means of support pins. The support pins are designed in such a way that a mechanical connection is created between the electrically heated honeycomb body and the so-called support catalyst, while simultaneously ensuring electrical insulation from the support catalyst. The support catalyst, as a so-called support structure, is mandatory in the applications known to date.

[0007] A disadvantage of the devices in the prior art is the need for an additional supporting catalyst for positioning the heating catalyst formed by the electrically heatable honeycomb body.

[0008] DE 10 2014 115 063 A1 discloses a device for treating exhaust gases, comprising an electrically heatable honeycomb body. The device has a support structure with pins that mechanically stabilize and electrically insulate the honeycomb body. The honeycomb body is heated by a current flow, which heats the exhaust gas and supports the catalytic conversion of the pollutants. The device aims to ensure a reliable mechanical connection and electrical insulation of the honeycomb bodies, particularly under changing thermal and mechanical conditions.

[0009] US 5,525,309 A describes a metallic honeycomb body with several axially arranged discs through which fluid flows along an axis. The discs have a plurality of channels through which the fluid is guided. The discs are connected by centrally arranged or symmetrically distributed supports that provide mechanical stability. The honeycomb body can be electrically heated, with electrical conduction paths running through the discs and supports to enable rapid heating of the fluid. Description of the invention, task, solution, advantages

[0010] Therefore, the object of the present invention is to provide a device for heating an exhaust gas flow, which can be arranged in the exhaust gas path of an internal combustion engine independently of an additional supporting catalyst and can thus be integrated into existing exhaust gas systems as easily as possible.

[0011] The object with regard to the device is achieved by a device for heating an exhaust gas stream having the features of claim 1.

[0012] One embodiment of the invention relates to a device for heating an exhaust gas flow from an exhaust gas source, comprising a honeycomb body through which flow can be carried along a main flow direction, which honeycomb body is produced from a plurality of metallic foils by stacking and winding them up, wherein the honeycomb body has at least one electrical conduction path which can be electrically contacted with two electrical contacts, wherein the device has at least one first frame element which is arranged upstream or downstream of the honeycomb body along the main flow direction, wherein the honeycomb body is connected to the first frame element by means of a plurality of support pins, wherein the at least one frame element has an annular section at its radially outer end region, wherein individual spokes run from this annular section to a central section and wherein the spokes are bent in a shovel shape.

[0013] Honeycomb bodies for exhaust gas aftertreatment are known in the prior art in a wide variety of designs. Metallic honeycomb bodies, in particular, are typically produced from a layer stack consisting of smooth or microstructured metal foils and corrugated metal foils. Flow channels are formed between the individual metal foils, through which air flows from an inflow side to an outflow side. The inflow side and the outflow side are formed by the end faces of the honeycomb body. The flow channels, or rather their orientation, define the main flow direction of the honeycomb body.

[0014] The layer stack is created by alternating stacking the metal foils on top of each other. The layer stack is then wound around one or more so-called winding mandrels, creating a honeycomb body with a disc-shaped configuration.

[0015] If the honeycomb body is electrically heated, the honeycomb body is designed such that current can flow from one end region of the honeycomb body to another end region, which is preferably opposite the first end region. This occurs along a conduction path. This preferably runs from an electrical contact at one end of the layer stack through the layer stack to the other end of the layer stack. When the honeycomb body is wound up, the conduction path runs regularly in the circumferential direction of the honeycomb body in the form of a spiral, with the individual sections of the layer stack being spaced from one another by a spiral air gap.

[0016] In designs known in the prior art, the electrically heatable honeycomb body is attached to another honeycomb body, such as a catalyst for exhaust gas aftertreatment, by means of support elements. The electrically heatable honeycomb body cannot therefore be used alone without the use of another honeycomb body serving as a supporting catalyst. To address this problem, the device according to the invention has at least a first frame element, which is positioned upstream or downstream of the honeycomb body along the main flow direction. The honeycomb body is attached to the frame element by means of support pins, which electrically insulate the honeycomb body from the frame.

[0017] The frame element is spaced apart from the honeycomb body along the main flow direction and is not in electrically conductive contact with the honeycomb body at any point. The frame element serves to connect the honeycomb body to a housing section of an exhaust pipe. In the simplest case, the exhaust pipe is formed by a circular tube. The frame element can be brought into contact with the inner surface of the exhaust pipe and connected to secure the honeycomb body in the exhaust pipe.

[0018] The exhaust pipe can also have cross-sections that deviate from a circular cross-section. The frame element is then preferably adapted to the respective internal cross-section of the exhaust pipe. The honeycomb body can nevertheless have a circular cross-section. Depending on the design, the honeycomb body can be connected to the other pole of a voltage source via a second electrical contact or simply be electrically connected to the housing of the exhaust pipe, provided this acts as the second pole. However, this should be avoided, particularly at high voltages, in order to prevent dangerous repercussions, such as electric shocks, and to avoid endangering people or animals.

[0019] The frame element is preferably designed in such a way that it has sufficient strength to position the honeycomb body permanently in the exhaust line and furthermore in such a way that the impairment of the flow through the honeycomb body is as minimal as possible and the counterpressure created by the frame element is as low as possible.

[0020] The at least one frame element has an annular section at its radially outer end region, with individual spokes extending from this annular section to a central section. The spokes are bent in a shovel shape.

[0021] It is particularly advantageous if a first frame element is arranged upstream of the honeycomb body along the main flow direction and a second frame element is arranged downstream along the main flow direction, wherein the first frame element and the second frame element are connected to the honeycomb body by means of a plurality of support pins.

[0022] By arranging two frame elements, improved positioning of the honeycomb body can be achieved. Doubling the frame elements also allows for an increase in the number of support points for the honeycomb body compared to the frame elements. Furthermore, this method makes it possible to connect the honeycomb body to the exhaust pipe housing twice via the frame elements.

[0023] Each of the frame elements is connected to the honeycomb body via several support pins, whereby the support pins create a mechanically durable connection.

[0024] It is also advantageous if the first frame element and / or the second frame element have a larger diameter than the honeycomb body. The larger diameter of the frame elements compared to the honeycomb body is particularly useful to prevent direct physical contact between the honeycomb body and the exhaust pipe housing. Because the frame elements are the only components that are crucial for connecting the honeycomb body to the exhaust pipe housing, the frame elements can be easily and cost-effectively adapted to the respective cross-sections of different exhaust pipes and housings, while the honeycomb body can remain unchanged.

[0025] A preferred embodiment is characterized in that the honeycomb body is electrically insulated from the first frame element and / or the second frame element by means of the support pins. Support pins serve, on the one hand, to mechanically fasten the honeycomb body to a fixed structure, in this case the frame elements, and, on the other hand, to electrically insulate the honeycomb body. Support pins are known in many different forms in the prior art and usually have a metal core which is partially or completely surrounded by an electrically insulating ceramic. For better connection to the honeycomb body and / or the frame element, metallic coatings can be applied to the insulating ceramic or metal sleeves can be inserted. The support pins can be materially connected to the honeycomb body and / or the heating conductor, for example by a soldering process, such as in particular high-temperature soldering.Alternatively, for example, and especially for connecting the support pins to the frame elements, butt soldering can be used as a joining method or the support pins can be welded to the frame elements.

[0026] It is also preferable if the first frame element and the second frame element are not identical and have different structural properties.

[0027] The upstream and downstream frame elements can each have a different structure. In particular, the frame elements can fulfill different functions. For example, it is conceivable to design one of the frame elements to ensure the highest possible insensitivity to so-called thermal shock events. Thermal shock events include, for example, sudden warm-up after a cold start or cooling after operation in a very cold environment. The activation or deactivation of the heating function can also be such events. To be able to withstand strong temperature fluctuations, special materials can be selected, or at least different strengths of the frame element can be created in certain sections, for example through different material thicknesses, connection types, or different materials.

[0028] An alternative optimization can be aimed at optimal vibration isolation, for example, to keep strong vibrations away from the honeycomb body. For this purpose, the frame element can have areas of higher flexibility and areas of lower flexibility, in particular to keep vibrations away from the areas of the frame element that accommodate the support pins.

[0029] Furthermore, it is advantageous if at least one of the frame elements is made from a plurality of sheet metal layers which are at least partially welded together.

[0030] Particularly preferably, the frame element is constructed like a leaf spring, so that several material layers are only partially connected to one another, allowing relative movement between the individual layers. This gives the frame element a certain degree of flexibility, which is particularly advantageous with regard to durability. The frame element thus forms a type of vibration damper, which can reduce the force applied to the heated honeycomb body.

[0031] Furthermore, it is advantageous if one of the frame elements has at least two areas with different material properties. The frame elements can be designed so that they have different properties across their cross-section. A particularly rigid design is conceivable at the connection points to the exhaust pipe and at the support pin receiving points, and a more flexible design in the areas in between. This leads to a certain decoupling of the honeycomb body from the vibrations of the exhaust pipe. Other material properties, such as strength, thermal conductivity, and flexibility, can also vary in certain sections.

[0032] The majority of exhaust pipes used in automotive construction have a circular cross-section. The annular section makes it particularly easy to connect the frame element to the pipe. Other shapes, such as oval cross-sections, are also possible. The annular section thus forms the anchor point for the frame element to the pipe or housing.

[0033] Since the honeycomb body extends over a large part of the flow cross-section of the pipeline and the honeycomb body has to be supported at several points relative to the frame element, spokes which protrude from the annular section are particularly advantageous in order to create a possibility in the center of the honeycomb body to support the honeycomb body relative to the frame element by means of support pins.

[0034] In an advantageous embodiment, the frame element has, in particular in the region of the center of the honeycomb body, a further annular element which serves to receive support pins.

[0035] Particularly preferably, the spokes and / or the annular sections follow the course of the layer stack of the honeycomb body, so that as little flow cross-section as possible is covered by the frame element and at the same time a straight connection of the honeycomb body to the frame element is possible by means of the support pins.

[0036] Furthermore, it is advantageous if the frame elements are aligned with one another at least in sections along the main flow direction.

[0037] Preferably, the frame elements are completely aligned with one another, so that the flow resistance generated by the frame elements is as low as possible. It is also conceivable for the frame elements to have flow-guiding properties, for example, to specifically target individual areas of the honeycomb body with exhaust gas.

[0038] The support pins can be designed such that they extend from the honeycomb body on one side to one of the frame elements and are connected to it. The flow element upstream in the main flow direction is thus connected to the honeycomb body via different support pins than the frame element downstream in the main flow direction. In this way, a different number of connection points can be created on the two frame elements. Furthermore, different support pins can be used for the two frame elements, for example, with a different insulating effect, a different material selection, or a different length or thickness.

[0039] Alternatively, the support pins can be designed such that they extend from the first frame element through the honeycomb body to the second frame element. The support pins penetrate the honeycomb body along a flow channel formed by the honeycomb body. The support pins can be connected to one of the frame elements on each side, or to only one of the frame elements. It is also possible for some of the support pins to be connected to both frame elements and some to only one frame element.

[0040] Depending on the application, it may be preferable to have a higher number of support pins in the winding center of the honeycomb than in the radially outer region of the honeycomb. This is because a large portion of the honeycomb's mass is located in the winding center. In principle, the number of support pins can be increased in locations where particularly high stability is required.

[0041] The connection of the support pins to the honeycomb body and / or the frame elements is preferably carried out by means of a material bond, for example by welding or soldering, in particular high-temperature soldering.

[0042] It is also expedient if the honeycomb body and / or the frame elements are arranged within an annular housing. The annular housing extends at least from the first frame element in the axial direction beyond the honeycomb body. If a second frame element is provided, this is also arranged within the annular housing.

[0043] A further embodiment of the invention relates to an exhaust gas aftertreatment device with at least one device as described above, wherein the exhaust gas aftertreatment device has a tubular housing, wherein the device is inserted into the housing, wherein the first frame element and / or the second frame element are connected to the housing in a materially bonded and / or form-fitting manner.

[0044] The tubular housing forms the receptacle for the device according to the invention. The tubular housing preferably has only a short axial extension of a few centimeters. Particularly preferably, the axial extension is approximately 2 centimeters. Required electrical feedthroughs, as known from the prior art, can be routed through the tubular housing, thus establishing contact with the honeycomb body. By connecting it to a tubular housing, the device becomes modular and can be integrated particularly easily into existing exhaust lines.

[0045] The exhaust pipe of an internal combustion engine can be connected to the tubular housing by means of a connecting element, such as pipe clamps. A material connection between the tubular housing and other sections of an exhaust pipe is also possible. In particular, the cross-sections of the tubular housing and the exhaust pipe can differ from each other in such a way that the components can be partially inserted into one another. Additionally, the components can be welded together, with the frame elements being welded to the tubular housing in particular.

[0046] The tubular housing may have a shoulder on its inner wall, which serves as a stop for one of the frame elements. The shoulder may, for example, be formed by a bead molded in from the outside.

[0047] Furthermore, it is expedient if the honeycomb body can be electrically contacted by means of at least one electrical feedthrough that extends through the housing. When using only one electrical feedthrough, the housing generally forms the second pole, so that the honeycomb body is electrically connected to the housing at one of its ends, preferably the end adjacent to the inner wall of the housing. In an alternative embodiment, the honeycomb body is contacted at each end by means of an electrical feedthrough, ensuring a current flow along the conduction path.

[0048] Advantageous further developments of the present invention are described in the subclaims and in the following description of the figures. Short description of the drawings

[0049] The invention is explained in detail below using exemplary embodiments with reference to the drawings. In the drawings: Fig. 1 is a view of a honeycomb body with a frame element in front and two electrical feedthroughs, Fig. 2 is a detailed view showing two frame elements with a honeycomb body arranged between them, Fig. 3 is a perspective view of two frame elements arranged in a tubular housing, Fig. 4 is a sectional view through a support pin which is connected to a frame element on one side, Fig. 5 is a sectional view through a honeycomb body and a support pin penetrating the honeycomb body, the support pin being connected to a frame element on both sides, and Fig. 6 is a sectional view through an alternative support pin which has an additional insulation layer in the axial direction compared to the frame elements. Preferred embodiment of the invention

[0050] The Figure 1shows a honeycomb body 1 formed by a wound stack of smooth and corrugated metal foils. The honeycomb body 1 is arranged behind a frame element 2 and connected to the frame element 2 by means of a plurality of support pins 3. At each end, the honeycomb body 1 is connected to an electrical feedthrough 4.

[0051] The electrical feedthroughs 4 are connected by a Figure 1 The electrical feedthroughs 4 are guided through a housing that cannot be seen and secured therein. The electrical feedthroughs 4 serve to supply an electrical conductor, whereby the electrical conductor is electrically insulated from the housing and the housing is sealed gas-tight by the electrical feedthroughs 4.

[0052] The frame element 2 has an annular section 5 at its outer radius and projecting spokes 6, which are curved in a shovel shape. The spokes 6 terminate in the center of the frame element in a second annular section 7. Arranged within the second annular section 7 is a further web 8, which covers the space defined by the second annular section 7.

[0053] The diameter of the frame element 2 is larger than the diameter of the honeycomb body 1. This ensures that when the frame element 2 is connected to a housing of an exhaust pipe, the honeycomb body remains spaced apart from the inner wall of the exhaust pipe and comes into contact with the exhaust pipe at most with one end region of the layer stack.

[0054] The Figure 2shows a sectional view through a support pin 10, which has a metallic core 11. The core 11 is coated with an electrical insulation 13, preferably an oxide ceramic, in the area of ​​the honeycomb body 12 shown. The insulation layer 13 is in turn enclosed by a metallic sleeve 14, which then contacts the metal foils of the honeycomb body 12. Furthermore, the core 11 is connected to the two frame elements 15, 16.

[0055] Figure 3 shows a perspective view of two frame elements 20, 21. In Figure 3 No honeycomb structure is shown between the two frame elements 20, 21. The frame elements 20, 21 are inserted into a tubular housing 22. For easier positioning, positioning means, such as corresponding projections and recesses, can be provided on the housing 22 and the frame elements 20, 21.

[0056] In the final assembled state, the electrical feedthroughs are also guided through the housing 22.

[0057] Figure 4 shows a support pin 30 connected on one side to a frame element 31. The support pin 30 also has a metallic core 32, an electrically insulating layer 33, and a metallic coating 34 for connection to the honeycomb body.

[0058] The support pin 30 is integrally connected to the frame element 31 on the outside, i.e. the side facing away from the honeycomb body.

[0059] Figure 5shows a support pin 43, which is connected at its ends to frame elements 41, 42 and to the honeycomb body 40. The structure of the support pin 43 corresponds to that of the previously shown support pins. Unlike the previous figures, the support pin 43 is connected to the frame elements 41, 42 on the inside, i.e., on the side facing the honeycomb body 40. More precisely, the solder paste for soldering the support pin 43 to the frame elements 41, 42 is applied to the inside.

[0060] Figure 6shows a support pin 50 with a slightly different structure. The metal core 51 is enclosed with an electrically insulating layer not only in the region 55, which is enclosed by a metal sleeve 52, which serves to accommodate the honeycomb body (not shown), but also in the regions 53 facing the frame elements (not shown). These regions 53 can be formed, for example, by washers made of oxide ceramic. This is followed by a metallic layer 54, which can be formed, for example, by a metallic washer.

[0061] Such a support pin has an increased insulation effect, since a separate insulation layer is also provided in the direction of the frame elements.

[0062] The examples of the Figures 1 to 6 In particular, they are not restrictive and serve to clarify the inventive concept. List of reference symbols

[0063] 01 Honeycomb body 02 Frame element 03 Support pin 04 Electrical feedthrough 05 Annular section 06 Spoke 07 Annular section 08 Web 10 Support pin 11 Metallic core 12 Honeycomb body 13 Insulation layer 14 Metal sleeve 15 Frame element 16 Frame element 20 Frame element 21 Frame element 22 Tubular housing 30 Support pin 31 Frame element 32 Metallic core 33 Insulation layer 34 Metal sleeve 40 Honeycomb body 41 Frame element 42 Frame element 43 Support pin 50 Support pin 51 Metallic core 52 Metal sleeve 53 Insulation layer 54 Metallic layer 55 Insulation layer

Claims

1. Device for heating an exhaust gas stream from an exhaust gas source, with a honeycomb body (1, 12, 40) through which gas can flow in a main flow direction, which is produced from a plurality of metallic foils by stacking and winding, wherein the honeycomb body (1, 12, 40) comprises at least one electrical conduction path which can be electrically contacted by two electrical contacts, wherein the device comprises at least one first frame element (2, 15, 16, 20, 21, 41, 42) which is positioned upstream or downstream of the honeycomb body (1, 12, 40) along the main flow direction, wherein the honeycomb body (1, 12, 40) is connected to the first frame element (2, 15, 16, 20, 21, 41, 42) by means of a plurality of supporting pins (3, 10, 30, 43, 50), wherein the at least one first frame element (2, 15, 16, 20, 21, 41, 42) comprises an annular section (5) at its radially outer end area, wherein individual spokes (6) running from this annular section (5) to a central section (7), characterized in that the spokes (6) are bent in the shape of a shovel.

2. Device according to claim 1, characterized in that a first frame element (2, 15, 16, 20, 21, 41, 42) is positioned upstream of the honeycomb body (1, 12, 40) along the main flow direction and a second frame element (2, 15, 16, 20, 21, 41, 42) is positioned downstream along the main flow direction, wherein the first frame element (2, 15, 16, 20, 21, 41, 42) and the second frame element (2, 15, 16, 20, 21, 41, 42) is connected to the honeycomb body (1, 12, 40) by means of a plurality of supporting pins (3, 10, 30, 43, 50).

3. Device according to one of the preceding claims, characterized in that the first frame element (2, 15, 16, 20, 21, 41, 42) and / or the second frame element (2, 15, 16, 20, 21, 41, 42) have a larger diameter than the honeycomb body (1, 12, 40).

4. Device according to one of the preceding claims, characterized in that the honeycomb body (1, 12, 40) is electrically isolated against the first frame element (2, 15, 16, 20, 21, 41, 42) and / or the second frame element (2, 15, 16, 20, 21, 41, 42) by means of the supporting pins (3, 10, 30, 43, 50).

5. Device according to one of the preceding claims, characterized in that at least one of the frame elements (2, 15, 16, 20, 21, 41, 42) is made from a plurality of sheet metal layers which are at least partially welded to one another.

6. Device according to one of the preceding claims, characterized in that one of the frame elements (2, 15, 16, 20, 21, 41, 42) comprises at least two areas of different material properties.

7. Device according to one of the preceding claims, characterized in that the frame elements (2, 15, 16, 20, 21, 41, 42) are aligned with one another at least in sections along the main flow direction.

8. Device according to one of the preceding claims, characterized in that the honeycomb body (1, 12, 40) and / or the frame elements (2, 15, 16, 20, 21, 41, 42) are arranged within an annular housing (22).

9. Exhaust gas aftertreatment device with at least one device according to one of the preceding claims, wherein the exhaust gas aftertreatment device comprises a tubular housing, characterized in that the device is inserted into the housing (22), wherein the first frame element (2, 15, 16 , 20, 21, 41, 42) and / or the second frame element (2, 15, 16, 20, 21, 41, 42) is connected to the housing (22) in a materially bonded and / or form-fitting manner.

10. Exhaust gas aftertreatment device according to claim 9, characterized in that the honeycomb body (1, 12, 40) can be electrically contacted by means of at least one electrical feedthrough (4) which is led through the housing (22).