DE102022129142A1 - Electrically heated unit - Google Patents

Abstract

An electrically heatable unit for use in a gas flow, in particular for an exhaust gas aftertreatment device of an internal combustion engine, comprises an electrically conductive base body through which the gas flow can flow, in particular a catalyst substrate, with an end face on the current input side, with an end face on the current output side and with a peripheral surface arranged between the end faces. The electrically heatable unit also comprises a heating device with at least one first electrode and with at least one second electrode. At least one of the electrodes, in particular both electrodes, comprises an electrically conductive layer which is arranged on an outer surface of the base body or applied to it and which is electrically conductively connected to the base body, an electrically conductive contact element arranged at a distance from the electrically conductive layer and an electrically conductive, flexible connection structure which is arranged between the electrically conductive layer and the electrically conductive contact element and contacts both the electrically conductive layer and the electrically conductive contact element.

Description

The invention relates to an electrically heatable unit for use in a gas stream, in particular for an exhaust gas aftertreatment device - in particular for catalytic exhaust gas aftertreatment - of an internal combustion engine.

In modern motor vehicles, both fuel consumption and the emission of pollutants such as nitrogen oxides are playing an increasingly important role. On the one hand, this is required by the emissions regulations of the regulatory authorities, and on the other hand, consumers' environmental awareness is increasing, so that consumers are already taking ecological aspects into account when making purchasing decisions.

Catalysts are used, among other things, for exhaust gas treatment in vehicles. Conventional catalysts usually comprise a base body made of electrically non-conductive ceramic (honeycomb body with channels), whereby the catalyst base body is coated with a catalyst material (for example metals from the platinum group, so-called platinum group metals - PGM). The catalyst material is applied to the base body in a very thin and porous layer (so-called wash coat).

Catalysts can only efficiently convert pollutant emissions, i.e. convert them into less harmful gas emissions, once they reach a certain minimum temperature - also known as the "light-off temperature". This minimum temperature is around 250°C to 280°C, but can be up to around 400°C to 800°C in aged catalysts. To reach these temperatures, the catalyst is heated by the hot exhaust gases from a combustion engine flowing through it. Depending on where the catalyst is located in the exhaust system, it can take some time for the catalyst to reach the required minimum temperature. Often, efforts are made to position the catalyst as close to the engine as possible in order to heat it up as efficiently and, above all, quickly as possible. Another way to reach the minimum temperature more quickly is to heat the catalyst. For this purpose, a heating disk can be provided on the catalyst base body upstream of the catalyst base body, which introduces heated air into the catalyst base body and thus preheats the catalyst.

Directly heated catalysts (electrically heated catalysts - EHC) help to significantly shorten the time until the light-off temperature is reached. With EHC, a potential difference is created by applying an electrical voltage directly to the catalyst base body, which ultimately causes the catalyst to heat up through resistance heating. To make this possible, the electrically heated catalyst base body is made of a conductive material. A voltage applied to the conductive material leads to heating of the catalyst through the resulting potential difference due to the electrical resistance of the conductive material. However, complete heating, i.e. heating of the entire catalyst material, especially inside the catalyst, takes a certain amount of time even with the known directly heated catalysts, which in turn means that the catalyst is only fully functional after this certain amount of time in order to convert most of the pollutants from the exhaust gas into harmless substances.

One of the biggest challenges with electrically heated units with an electrically conductive substrate (ELS), such as catalysts, is the electrical contact. The ELS, for example a semi-ceramic conductive carrier material, can be provided with a metallic contact at suitable points, for example by a direct connection between metal and ELS, in order to be able to introduce the electrical current from a power source (battery or power electronics/output stage) into the ELS. This contact should also be selected in such a way that an effective current supply for the heating output is possible. In addition, there should be a stable, permanent connection between the electrically conductive substrate and the contact so that an assembly can withstand the demands of the vehicle's life.

Electrodes, preferably made of metal, can be provided for supplying current and thus heating an electrically conductive substrate of a base body of the electrically heatable unit. Direct electrical contact between the electrodes and the base body can be problematic for several reasons. For example, different thermal expansion of metals and ceramics can make a direct connection between the two components, e.g. by soldering, impossible or at least prone to errors. The connection can be severed by different expansion of the materials when exposed to heat, so that effective current supply to the base body can no longer be guaranteed. A further problem can arise from possible oxidation processes on the ceramic of the base body, which can lead to an electrically passivated (non-conductive) oxide layer on the surface of the base body. It can therefore be advantageous to protect the contact from oxygen. However, mechanical pressing of the electrodes is not possible, especially at higher temperatures. With a Very high current densities can arise in the ceramic of the base body with point-based contact. The higher resistance of the ELS, for example in comparison to a metallic connection, can lead to a very strong temperature development that can even destroy the base body. Further problems with point-based direct contact can arise from the possible transmission of force through the electrical connections to the tension-sensitive ceramic as well as from large surface tolerances in extruded ceramic bodies (roundness, surface roughness, etc.). A surface contact between the electrodes and the base body can be advantageous and lead to a more even heating of the base body.

The problem underlying the invention was described above purely by way of example using an application from exhaust gas technology. However, similar problems also arise in other areas, e.g. in process technology.

It is an object of the invention to provide a device which enables a stable and permanently functional connection between an electrically conductive substrate and a contact for supplying current to a heatable unit, for example a catalyst or a heating disk, than known devices from the prior art.

This object is achieved by an electrically heatable unit having the features of claim 1.

According to a first aspect of the invention, an electrically heatable unit has an electrically conductive base body and a heating device. The electrically conductive base body, in particular a catalyst substrate, has an end face on the current input side, an end face on the current output side and a peripheral surface arranged between the end faces and is flowed through by the gas flow. The heating device comprises at least one first electrode and at least one second electrode. At least one of the electrodes, in particular both electrodes, comprises an electrically conductive layer which is arranged on an outer surface of the base body or applied to it and which is electrically conductively connected to the base body, an electrically conductive contact element arranged at a distance from the electrically conductive layer and an electrically conductive, flexible connection structure which is arranged between the electrically conductive layer and the electrically conductive contact element and contacts both the electrically conductive layer and the electrically conductive contact element.

The electrically heatable unit can be designed as a cleaning unit, for example as a catalyst, or as a heating unit, for example as a heating disk. The internal combustion engine can be designed as an internal combustion engine, for example as a gasoline engine or diesel engine. The internal combustion engine can also implement other combustion processes, for example a Miller combustion process, or use other fuels, for example synthetic fuels or hydrogen. When such a machine is operated, pollutants are produced. The pollutant concentrations can depend heavily on the operating conditions, for example on the type of fuel, the concentration of the fuel in the fuel-air mixture used, the amount of the fuel-air mixture, the speed of the internal combustion engine and/or the operating temperature of the internal combustion engine.

The exhaust gases produced by combustion in the internal combustion engine form a gas flow. The exhaust gases are guided to the outside via an exhaust system connected to the internal combustion engine through an exhaust aftertreatment device, i.e. released into the ambient air of the vehicle. The exhaust aftertreatment device generally comprises at least one base body through which the gas flow flows, essentially parallel to a longitudinal axis of the base body. The term "essentially" refers to the fact that the gas flow does not have to run parallel to a longitudinal axis of the base body, especially on the front face on the flow inlet side (i.e. at the inlet of the base body) and on the front face on the flow outlet side (i.e. at the outlet of the base body), for example due to the design. Flow deviations, for example less than 20° to a longitudinal axis of the base body, can also be possible inside the base body. The essentially parallel flow of the exhaust gas to a longitudinal axis of the base body means that a low exhaust back pressure can be achieved within the exhaust system, which reduces a loss of power and increased consumption of the internal combustion engine. However, other structures of a base body through which a gas flow flows are also conceivable, for example printed structures. With such structures, flow deviations inside the structures of up to 90° to a longitudinal axis of the base body are possible. Such structures can be advantageous in terms of heat transfer from the electrically heatable unit to the gas flow flowing through it or in terms of reactivity through better mixing of the gas flow.

The electrically conductive base body of an electrically heated catalyst (EHC), other cleaning units or other electrically Heatable units for use in a gas stream have so far often been manufactured from metal, which is a complex process. By using a semi-ceramic carrier material, which can also be made electrically conductive and directly heatable, for example by adding metallic additives to a ceramic substrate before the sintering process, the advantages of ceramic, such as a significantly lower density and thus weight advantages or lower production costs, compared to metallic carriers, can be exploited. The advantage of directly heating the ceramic base body, which can be electrically powered and heated, is higher efficiency and faster heating behavior, since, for example, in contrast to heatable catalysts/cleaning units that are heated with the help of a heating disk, the heating does not have to go via the detour of heated air, i.e. the heating disk heats air that is fed to the base body of the catalyst/cleaning unit and thus heats the base body indirectly. In an EHC/cleaning unit with an electrically conductive substrate, the base body is directly supplied with current and thus directly heated.

The electrically conductive base body of a cleaning unit such as a catalyst or a particle filter can have channels arranged in a honeycomb shape. The honeycomb shape, in particular the thin-walled channels, increases the surface area of the base body. The thin-walled channels and the resulting increased surface area of the base body of a cleaning unit designed as a catalyst allow more exhaust gases to be converted into harmless substances from the gas flow of the internal combustion engine, since the increased surface area means that more exhaust gas volume comes into contact with the catalytically active coating (PGM WashCoat). Precious metals such as rhodium, platinum and palladium are applied to the surface of the base body, which catalytically convert the pollutants.

The at least one first electrode and the at least one second electrode of the heating device are made of electrically conductive elements. The first electrode can also function as an anode and the second electrode as a cathode, or vice versa. The electrodes contact - directly or indirectly - the electrically conductive honeycomb structure of the base body. By applying an external voltage to the electrodes, an electrical potential difference builds up between the first electrode and the second electrode, so that an electrical current flows. The electrically conductive base body represents an electrical resistance that leads to heating. With the help of a control unit, the current flow between the electrodes and thus the heating of the base body can be controlled. The greater this current flow, the hotter the electrically conductive base body becomes or the faster the electrically conductive base body heats up and - in the case of a catalyst - also the catalytic coating (PGM WashCoat) applied to the base body. The same applies to cleaning units of other designs, in particular particle filters or other heatable units, for example heating disks.

The electrically conductive layer is made of an electrically conductive material. The electrically conductive material has both temperature-stable and corrosion-resistant properties, for example heat-resistant metals such as nickel. In principle, all suitable metals that meet the requirements with regard to temperature and corrosion stability are suitable for forming the electrically conductive layer. A separate electrically conductive layer can be provided for each of the at least one first electrode and at least one second electrode. However, it is also possible to use a common electrically conductive layer for electrodes with the same potential. For example, a plurality of spaced-apart first electrodes can be subjected to a positive potential by means of the control unit. The majority of the first electrodes can have a common electrically conductive layer. The same applies to a plurality of spaced-apart second electrodes with the same potential. The at least one electrically conductive layer per electrode is arranged on an outer surface of the base body. The outer surface of the base body is understood to mean a side facing away from the peripheral surface surrounding the base body. The electrically conductive layer can be deposited galvanically on the outer surface of the base body. The layer thickness of the electrically conductive layer can depend on the current strength and the duration of the current supply during the galvanic treatment of the base body. During the galvanic treatment, the base body is placed in a galvanic bath. Areas of the outer surface of the base body where no electrically conductive layer is to be applied are taped off or protected by coatings. Another possibility for a targeted application or deposition of the electrically conductive layer on the outer surface of the base body can be to oxidize the base body before galvanization, whereby a non-conductive surface is applied to the outer surface of the base body. Then only target areas in which the electrically conductive layer is to be arranged are mechanically ground in order to remove the oxide layer in the target areas. In addition to a galvanic coating In addition to the method for applying the metallic layer to the outer surface of the base body, other methods are also conceivable, for example chemical deposition of the metallic layer or pressing on a thin metallic foil by, for example, magnetic pulse welding.

The electrically conductive contact element is designed to make contact with an electrically conductive connection to the control unit. The contact can be arranged on an outer surface of the contact element facing away from the base body or in the contact element, for example by making a contact in a bore in the contact element. The contact element can be evenly spaced from the electrically conductive layer and. Furthermore, the contact element can have the same size as the electrically conductive layer, i.e. a projection of the contact element spaced from the electrically conductive layer onto the electrically conductive layer can lead to an overlap without overlapping of the projected area of the contact element with the area of the electrically conductive layer. In other words, a two-dimensional extension (length and width) of the electrically conductive layer and a two-dimensional extension (length and width) of the contact element can be essentially the same size.

The electrically conductive, flexible connection structure can completely fill a space between the electrically conductive layer and the electrically conductive contact element, at least in sections. However, it is also possible for the connection structure to have only individual, discrete connection elements between the electrically conductive layer and the contact element. By contacting the connection structure with both the electrically conductive layer and the contact element, the connection structure represents a link between the contact element and the electrically conductive layer or the base body, which transmits a current flow supplied from outside (for example from a control unit) to the electrically heatable unit via contacting the contact element and thus enables the base body to be energized and heated.

The use of the unit according to the invention is not limited to exhaust technology. It is also possible to use the unit - in exhaust technology or in other areas - merely as a heating device with which a gas stream is heated without achieving a (catalytic) cleaning effect.

Further embodiments of the invention are set out below and in the dependent claims.

In some embodiments, the electrically heatable unit can further comprise at least one first contact fixation and at least one second contact fixation. The at least one first contact fixation can fix at least one first contact of the electrically conductive layer and the connection structure. The at least one second contact fixation can fix at least one second contact of the connection structure and the contact element. The at least one first contact fixation and the at least one second contact fixation can secure the connection structure against displacement or slipping. However, the connection structure is still arranged flexibly between the electrically conductive layer and the contact element. The connection structure can compensate for relative movements between the electrically conductive layer and the contact element without the electrically conductive connection (through the connection structure) between the electrically conductive layer and the contact element being interrupted. Fixing the connection structure can be particularly useful for mounting the electrically heatable unit in a housing (canning), since large forces and accelerations can occur here, which can cause the connection structure to shift or slip.

In such an embodiment, the first contact fixation and/or the second contact fixation can be designed as a solder layer at least in sections and/or can comprise solder points. The contact fixations by means of a solder layer can be advantageous because all or a large number of contacts between the connection structure and the electrically conductive layer and/or between the connection structure and the contact element can be fixed almost simultaneously. If the connection structure only comprises a small number of discrete connection elements, fixing the discrete connection elements by means of individual solder points can be advantageous.

In some embodiments, the electrically conductive layer can have a layer thickness between 10 µm and 100 µm, in particular between 30 µm and 80 µm, preferably between 40 µm and 60 µm, for example 50 µm +/- 5 µm. A sufficiently large layer thickness can promote both a stable electrically conductive connection between the electrically conductive layer and the electrically conductive base body, as well as a stable contact fixation of the electrically conductive, flexible connection structure to the electrically conductive layer. A larger layer thickness can be advantageous with regard to current distribution and/or for applying a contact fixation, for example a solder layer, to the electrically conductive layer. However, a smaller layer thickness can be advantageous in order to counteract different thermal expansions of the base body and the electrically conductive layer.

In some embodiments, the electrically conductive layer can extend substantially over an entire axial length in the axial direction of the base body. The entire axial length of the base body can describe a spatial extension of the base body in the axial direction of an axis of symmetry of the base body, starting at the current input-side end face of the base body up to the current output-side end face of the base body. The term "substantially" refers here to the fact that the electrically conductive layer can be formed, for example, up to or close to the current input-side end face and up to or close to the current output-side end face of the base body, i.e. the at least one electrically conductive layer (and thus the at least one electrode) can be formed in such a way that the at least one electrically conductive layer does not quite reach the edges, i.e. the current input-side end face and the current output-side end face, of the base body in sections. However, it is also possible for the electrically conductive layer, starting at the front face of the base body on the power input side, to extend in the axial direction over a maximum of 10%, 15%, 25% or up to 50% of the base body. Such a limited electrically conductive layer starting at the front face of the base body on the power input side can have the advantage that an inlet area of the base body in particular can be quickly and efficiently brought to the required minimum temperature in order to clean the incoming exhaust gas. The gas heated in the inlet area then efficiently heats downstream areas of the base body.

In some embodiments, two or more first electrodes and/or two or more second electrodes can be provided. A more effective and targeted supply of current to the base body and thus also heating of the base body can be achieved by a plurality of first and second electrodes. The two or more first electrodes can each have the same electrical potential (positive potential: plus pole or negative potential: minus pole). The two or more second electrodes can have an electrical potential that is opposite to the electrical potential of the two or more first electrodes. If, for example, the two or more first electrodes have a positive potential, the two or more second electrodes can have a negative potential, and vice versa. A potential difference (voltage) can build up between a first electrode and a second electrode if the first electrode has a different potential than the second electrode. The at least two or more first electrodes and the at least two or more second electrodes can be arranged at a distance from one another on the peripheral surface of the base body.

In some embodiments, at least one first electrode can be arranged on a peripheral surface of the base body, in particular wherein the at least one first electrode can be closed in the peripheral direction. Alternatively or additionally, at least one second electrode can be arranged on the peripheral surface of the base body, in particular wherein the at least one second electrode can be closed in the peripheral direction. The at least one first electrode can be arranged in the region of the current input-side end face on the peripheral surface of the base body. The at least one second electrode can be arranged in the region of the current output-side end face on the peripheral surface of the base body.

In some embodiments, at least one first electrode can be arranged on an end face of the base body and/or at least one second electrode can be arranged on an end face of the base body. The at least one first electrode can be arranged on the end face of the base body on the current input side. The at least one second electrode can be arranged on the end face of the base body on the current output side. When arranging an electrode on an end face of the base body, it must be taken into account that a sufficiently large flow of a gas stream through the base body is possible.

In some embodiments, the electrically conductive contact element can be a sheet metal component that is curved or flat at least in sections. In particular, the sheet metal component can have at least a section-wise shape of the base body and/or at least a section-wise shape of a housing in which the base body is arranged. This can enable simple assembly of the electrically heatable unit in the housing. The sheet metal component can also be designed in such a way that contacting is possible for energizing the contact element; in particular, the contact element or the sheet metal part can have a recess for a sleeve.

In some embodiments, the electrically conductive contact element may consist of a tem temperature-stable and/or corrosion-resistant material, particularly stainless steel. The contact element can be exposed to high temperatures. A temperature-stable or heat-resistant design of the contact element can ensure reliable functionality even at high temperatures, for example contact from the outside to supply power to the electrically heated unit. In addition, designing the contact element with a corrosion-resistant material can counteract a deterioration in contact capability due to oxidation.

In some embodiments, the electrically conductive, flexible connection structure can have an irregular structure, in particular the connection structure can comprise a wire mesh. The wire mesh can comprise a plurality of wires. The wires can have a spiral, a wound, a braided or an undirected, for example a chaotic structure. The irregular structure of the electrically conductive connection structure can also be formed from a flexible metal foam. The irregular structure of the connection structure extends from the electrically conductive layer or from a first contact fixation to the contact element or to a second contact fixation, so that an electrically conductive connection is formed between the electrically conductive layer and the contact element through the connection structure.

In alternative embodiments, the electrically conductive, flexible connection structure can have a regular structure, in particular the structure can have a plurality of discrete connection elements, which are preferably prestressed in the radial direction. Each of the discrete connection elements can have a straight, angled or directional structure. The plurality of discrete connection elements of the connection structure can comprise individual bent sheet metal elements, each of which is clamped between the electrically conductive layer and the contact element. The sheet metal elements can be punched out of the contact element at least in sections and bent in the direction of the electrically conductive layer. Each of the discrete connection elements has a length that is greater than the distance between the electrically conductive layer and the contact element. In addition, each of the discrete connection elements extends from the electrically conductive layer or from a first contact fixation to the contact element or to a second contact fixation, so that an electrically conductive connection is formed between the electrically conductive layer and the contact element through each of the discrete connection elements.

In some embodiments, the electrically heatable unit can further comprise a sleeve with an internal thread, wherein the sleeve is connected to the contact element in an electrically conductive manner and extends in the direction of the base body. The sleeve can be welded onto the contact element of the electrically heatable unit. The sleeve can be designed to contact the contact element, in particular to receive an electrically conductive pin via the internal thread of the sleeve. Power can thus be supplied to the electrically heatable unit via the sleeve.

In such an embodiment, one end of the sleeve can be essentially flush with the contact element. The term "flush" in this context means that a slight overhang of the sleeve beyond the contact element is possible. The overhang beyond the contact element is smaller than the distance between the housing and the contact element when the electrically heatable unit is installed. This makes it possible to insert the electrically heatable unit into the housing without the sleeve touching the housing. Damage to the housing or the sleeve can thus be avoided.

In such an embodiment, one end of the sleeve can extend into a base body bore of the base body, the base body bore having a larger diameter than a diameter of the sleeve. The base body bore must be made before the heating device is mounted on the base body. The base body bore is designed to accommodate one end of the sleeve without the end of the sleeve and the base body touching. When the electrically heatable unit is energized via a pin arranged in the sleeve, no direct current can flow between the sleeve and the base body. The current flows via the heating device, thus avoiding a point-by-point current introduction through the base body bore. An undersize sleeve compared to the base body bore of the base body can also counteract damage to the base body in the event of thermal expansion caused by energization of the (metal) sleeve.

In some embodiments, the electrically heatable unit may further comprise a pin that is electrically conductively connected to the contact element, wherein the pin extends in a direction away from the base body. The pin may be formed from an electrically conductive material. One end of the pin may contact the contact element the electrically heatable unit in an electrically conductive manner. In particular, the pin can be welded onto the contact element or the pin can be screwed into the sleeve and thus be connected to the contact element in an electrically conductive manner. Another end of the pin can be connected to a control unit, whereby the control unit can be used to supply current to the electrically heatable unit. The current supply generates a potential difference between the at least two electrodes of the electrically heatable unit. The potential difference can be controlled as required.

In some embodiments, the electrically heatable unit can be clamped in a housing. The housing can be made of a metal, for example stainless steel. The housing can have an inlet and an outlet. A gas flow, in particular an exhaust gas flow from an internal combustion engine, can flow through the inlet. The gas flow flowing into the housing can flow through the electrically heatable unit inside the housing and exit the housing again through the outlet of the housing. The electrically heatable unit can be clamped in the housing by means of at least one bearing mat.

In such an embodiment, at least one bearing mat can be arranged between the housing and the base body, in particular between the housing and the contact element. The at least one bearing mat can be made of an electrically insulating, temperature-resistant material, for example high-temperature wool. The bearing mat can surround the base body of the electrically heatable unit at least in sections, in particular completely. The electrically heatable unit can be fixed in the housing by means of the bearing mat and insulated from the housing.

In an alternative embodiment, two or more bearing mats can be arranged between the housing and the base body, wherein at least one bearing mat can be arranged between the housing and the contact element. A first bearing mat can accommodate the heating device described here, so that the at least two electrodes of the heating device are fixed by the first bearing mat. The first bearing mat can have recesses to accommodate the at least two electrodes of the heating device. The first bearing mat can surround the base body of the electrically heatable unit at least in sections, in particular completely, and can be flush with an outer surface of the contact element facing the housing. The term "flush" in this context means that the outer surface of the contact element facing the housing is accessible for contacting and is not covered by the first bearing mat. The second bearing mat can in particular lie flat on the first bearing mat. In order to enable contacting of the contact element via the outer surface of the contact element facing the housing, the second bearing mat can have a recess. The recess in the second bearing mat can be smaller than the recess in the first bearing mat. The second bearing mat covers part of the outer surface of the contact element facing the housing and thus fixes and insulates the contact element against the housing.

The present invention further relates to an exhaust system having an exhaust aftertreatment device with an electrically heatable unit according to at least one of the embodiments described above.

The invention also relates to a vehicle with an internal combustion engine connected to an exhaust system of the type described above.

• 1A zeigt eine perspektivische Darstellung einer Ausführungsform einer elektrisch beheizbaren Reinigungseinheit mit einer Heizeinrichtung,
• 1 B zeigt einen Ausschnitt der elektrisch beheizbaren Reinigungseinheit in schematischer Schnittdarstellung gemäß 1A,
• 2 zeigt einen weiteren Ausschnitt der elektrisch beheizbaren Reinigungseinheit in schematischer Schnittdarstellung,
• 3 zeigt eine schematische Schnittdarstellung einer Ausführungsform einer elektrisch beheizbaren Reinigungseinheit mit einer Heizeinrichtung in einem Gehäuse,
• 4 zeigt eine schematische Schnittdarstellung einer weiteren Ausführungsform einer elektrisch beheizbaren Reinigungseinheit mit einer Heizeinrichtung,
• 5 zeigt eine perspektivische Darstellung einer Ausführungsform einer elektrisch beheizbaren Reinigungseinheit mit zwei Lagermatten,
• 6 zeigt eine schematische Schnittdarstellung einer Ausführungsform einer elektrisch beheizbaren Reinigungseinheit gemäß 3 mit einer Kontaktierung über eine Hülse, und
• 7 zeigt eine schematische Schnittdarstellung einer weiteren Ausführungsform einer elektrisch beheizbaren Reinigungseinheit gemäß 3 mit einer Kontaktierung über einen aufgeschweißten Pin.

The invention is described below purely by way of example using embodiments which are used in exhaust gas technology, with reference to the drawings.

• 1A shows a perspective view of an embodiment of an electrically heatable cleaning unit with a heating device,
• 1 B shows a section of the electrically heated cleaning unit in a schematic sectional view according to 1A ,
• 2 shows another section of the electrically heated cleaning unit in a schematic sectional view,
• 3 shows a schematic sectional view of an embodiment of an electrically heatable cleaning unit with a heating device in a housing,
• 4 shows a schematic sectional view of another embodiment of an electrically heatable cleaning unit with a heating device,
• 5 shows a perspective view of an embodiment of an electrically heated cleaning unit with two bearing mats,
• 6 shows a schematic sectional view of an embodiment of an electrically heatable cleaning unit according to 3 with contact via a sleeve, and
• 7 shows a schematic sectional view of another embodiment of an electrically heatable cleaning unit according to 3 with contact via a welded pin.

1A shows a perspective view of an embodiment of an electrically heatable cleaning unit 100 with a heating device for the (catalytic in the present example) treatment of a gas flow with an electrically conductive base body 102, in particular a catalyst substrate. In the embodiment shown, the base body 102 is cylindrical and its extent is limited by a current input side end face 110, a current output side end face 112 and a peripheral surface 104 arranged between the end faces 110, 112. The base body 102 can also be shaped differently. Within the space limited by the end faces 110, 112 and the peripheral surface 104, the base body 102 has a honeycomb structure 103, wherein the honeycomb structure 103 forms a plurality of thin-walled channels.

The base body 102 can be flowed through by a gas flow, in particular by an exhaust gas flow from an internal combustion engine. The gas flow flows through the base body 102 in the flow direction 130 of the gas flow, with the gas flow flowing into the base body 102, in particular into the thin channels of the honeycomb structure 103, at the flow inlet side end face 110 of the base body 102. The gas flow is guided in the flow direction 130 through the honeycomb structure 103 of the base body 102 until the gas flow exits again at the flow outlet side end face 112 of the base body 102. The channels of the honeycomb structure 103 of the base body 102 run essentially parallel to the flow direction 130 of the gas flow. The base body 102 is preferably designed to be rotationally symmetrical to an axis of symmetry A. In the embodiment shown, the axis of symmetry A corresponds to the longitudinal axis of the base body 102.

In this embodiment, the heating device of the electrically heatable cleaning unit 100 comprises a first electrode 106 and a second electrode 108, which are arranged at a distance from one another on the peripheral surface 104 of the base body 102. In other embodiments, the heating device can also comprise more than one first electrode 106 and/or more than one second electrode 108. The electrodes 106, 108 are electrically conductively connected to the peripheral surface 104 of the base body 102. By applying, for example, a negative electrical potential (minus pole) to the first electrode 106 and a positive electrical potential (plus pole) to the second electrode 108, a voltage field is generated between the first electrode 106 and the second electrode 108. It is also possible to apply a positive electrical potential to the first electrode 106 and a negative electrical potential to the second electrode 108. Due to the different polarity of the first electrode 106 and the second electrode 108, a potential difference (voltage) is formed between the first electrode 106 and the second electrode 108. The formation of the potential difference can be controlled as required by a control unit (not shown) which is assigned to the heating device. When a voltage is applied, an electrical current flows between the first electrode 106 and the second electrode 108. The electrical current causes areas between the first electrode 106 and the second electrode 108 to heat up thermally due to an electrical resistance of the electrically conductive base body 102, and thus the base body 102 is heated.

At least one of the electrodes 106, 108, in particular both electrodes 106, 108, comprises an electrically conductive layer 114, an electrically conductive contact element 116 and an electrically conductive, flexible connection structure 118. The electrically conductive layer 114 is arranged on an outer surface of the base body 102 or applied thereto. Furthermore, the electrically conductive layer 114 is electrically conductively connected to the base body 102. The electrically conductive layer 114 can extend starting at the current input side end face 110 in the axial direction of the axis of symmetry A over 10%, 15%, 25%, 50% of the axial length of the base body 102 or over the entire axial length of the base body 102 and have a substantially constant layer thickness.

The connection structure 118 and the contact element 116 of the electrodes 106, 108 have essentially the same axial extension as the electrically conductive layer 114. The term “essentially” in this context means that the electrically conductive layer 114 and/or the contact element 116 can have a slightly larger axial extension, in the range of a few centimeters, than the connection structure 118.

The electrically conductive contact element 116 is arranged in the radial direction away from the base body 102 at a distance from the electrically conductive layer 114. The contact element 116 can be designed as a sheet metal component so as to be curved at least in sections. In other embodiments, the contact element 116 can also be designed to be flat at least in sections. A distance between the contact element 116 and the electrically conductive layer 114 can be designed to be the same size, ie the contact element 116 can be arranged parallel and offset to the electrically conductive layer 114.

The electrically conductive, flexible connection structure 118 is arranged in the space delimited by the electrically conductive layer 114 and the contact element 116. The connection structure 118 contacts both the layer 114 and the contact element 116, i.e. the connection structure 118 is electrically conductively connected to both the electrically conductive layer 114 and the electrically conductive contact element 116. The connection structure 118 can be designed as an irregular structure, for example as a wire mesh, or as a regular structure with a plurality of discrete connection elements that are prestressed in the radial direction.

1B shows a section of the electrically heatable cleaning unit 100 in a schematic sectional view through a cutting plane E of the embodiment according to 1A . The 1B The layer structure of an electrically heatable cleaning unit 100 according to the invention shown comprises the following elements: a base body 102 with a honeycomb structure 103, for example of a catalyst, an electrically conductive layer 114, a first contact fixation 120, a connecting structure 118, a second contact fixation 121 and a contact element 116. The elements are arranged in layers in a radial outward direction, away from the base body 102. The electrically conductive layer 114 is applied to an outer surface of the base body 102. The first contact fixation 120 fixes at least a first contact of the electrically conductive layer 114 and the connection structure 118. In other words, the first contact fixation 120 fixes at least one point or at least one area of the connection structure 118 to the electrically conductive layer 114. As a result, the connection structure 118 is fixed to the electrically conductive layer 114 against translational and rotational movements. The connection structure 118 is also fixed to the contact element 116 by means of the second contact fixation 121. The second contact fixation 121 consequently fixes at least a second contact of the connection structure 118 and the contact element 116. The connection structure 118 is fixed to the contact element 116 by means of the second contact fixation 121 at least in one point or at least in one area. As a result, the connection structure 118 is fixed to the contact element 116 against translational and rotational movements.

The electrically conductive layer 114 can be made of a metal layer, for example of galvanically deposited nickel. The layer 114 can protect the base body 102, for example an electrically conductive substrate, from oxidation and at the same time form a contact surface for at least a first contact fixation 120. The electrically conductive layer 114 has a layer thickness that does not hinder the thermal expansion of the base body 102. For example, the layer thickness of the electrically conductive layer 114 can be between 10 µm and 100 µm, in particular between 30 µm and 80 µm, preferably between 40 µm and 60 µm (eg 50 µm +/- 5 µm). The first contact fixation 120 and/or the second contact fixation 121 can be formed at least in sections as a solder layer and/or can comprise solder points (see 2 ), wherein the electrically conductive layer 114 can be designed to facilitate application of the solder points or the solder layer.

2 shows a further section of the electrically heatable cleaning unit 100 in a schematic sectional view. The first contact fixation 120 is designed in this embodiment as a plurality of solder points 122. The solder points 122 can enable the connection structure 118, designed as a wire mesh 124, to be fixed to the electrically conductive layer 114 and consequently also enable the connection structure 118 or the wire mesh 124 to be fixed to the base body 102. The solder points 122 (or the first contact fixation 120) can prevent or limit a relative movement of the base body 102 and the wire mesh 124 and thus counteract mechanical abrasion of the base body 102 or the wire mesh 124. In addition, the first contact fixation 120 in the form of solder points 122 or in the form of a solder layer (not shown) can protect the electrically conductive layer 114 at the contact points from environmental influences. According to the 2 shown section of the first contact fixation 120, a second contact fixation 121, for example a further soldering by solder points 122 as a fixation between the wire mesh 124 and the contact element 116, can take place. The second contact fixation can also be designed as a plurality of solder points 122 or as a solder layer and prevent or limit a relative movement of the wire mesh 124 and the contact element 116. At higher application temperatures, this soldering or a fixation of the connection structure 118 is decisive.

The wire mesh 124 can represent a compensating component between a ceramic of the base body 102 of a catalyst and the contact element 116. The connecting structure 118 or the wire mesh 124 can compensate for different thermal expansions and create a tolerance compensation between an uneven ceramic surface of the base body 102 and the contact element 116. Furthermore, the connecting structure 118 can be used for a mechanical Decoupling between the contact element 116 and the base body 102, so that, for example, forces on the contact element 116 (eg via a connection pin) are not transferred directly to the ceramic of the base body 102. Instead of the 2 Different embodiments of a connection structure 118 required in the respective application area can be used for the wire mesh 124 shown, in particular electrically conductive, flexible connections. The electrically conductive contact element 116 can be made of a temperature-stable and/or corrosion-resistant material, in particular stainless steel. The contact element 116 can promote a uniform, flat current distribution between a connection, for example by means of a pin or a sleeve, and the ceramic of the base body 102.

3 shows a schematic sectional view of an embodiment of an electrically heatable cleaning unit 100 with a heating device in a housing 126. The layer structure of the electrically heatable cleaning unit 100 can be one of the 1 A , 1B and 2 described embodiments. The electrically heatable cleaning unit 100 is arranged in a housing 126. The housing 126 can be made of metal. Electrical insulation of the electrically heatable cleaning unit 100 from the housing 126 is achieved via an electrically insulating, optionally intumescent bearing mat 128, which is arranged between the housing 126 and the contact element 116. In addition to the electrical insulation of the electrically heatable cleaning unit 100 from the housing 126, the bearing mat 128 can also fix the electrically heatable cleaning unit 100 in the housing 126. Several bearing mats 128, in particular two electrically insulating bearing mats 128 (see 5 ), for the insulation and fixation of the electrically heatable cleaning unit 100.

4 shows a schematic sectional view of a further embodiment of an electrically heatable cleaning unit 100 with a heating device. Alternatively or in addition to contacting the electrodes 106, 108 on an outer surface of the base body 102, contact can also be made via the current input side end face 110 and/or the current output side end face 112. A first electrode 106 can be arranged on the current input side end face 110 of the base body 102. It must be taken into account that a sufficiently large flow of a gas stream in the flow direction 130 along an axis of symmetry A through the base body 102 is possible. For example, the first electrode 106 can be ring-shaped and arranged at least in sections on an edge region of the base body 102, so that a large part of the circular cross section (with a cylindrical design of the base body 102) can still be flowed through by the gas stream. The first electrode 106 can be closed in particular in the circumferential direction. The first electrode 106 can comprise a connecting structure 118 as described herein. The connecting structure 118 can be designed as a wire mesh ring in accordance with the annular geometry of the first electrode 106. The wire mesh ring can be applied to the base body 102 or to an electrically conductive layer 114 (in 4 not shown). Contacting or energizing the first electrode 106 can be done via at least one clamping contact that is arranged between the wire mesh ring and a support ring 132. The support ring 132 can be arranged all the way around, on the power input side of the base body 102. Alternatively, energizing the first electrode 106 can also be done via a connection contact that is soldered directly onto the wire mesh ring. The contacting of the first electrode 106 can be electrically connected to a control unit, as described herein.

The first electrode 106 arranged on the current input side face 110 of the base body 102 can be fixed against a housing 126 (not shown) and electrically insulated by support rings 132. The support rings 132 are made of electrically insulating material in order to prevent current from being supplied to the housing 126.

The second electrode 108 can be arranged on the current output-side end face 112 of the base body 102, for example centered around the axis of symmetry A of the base body 102. The second electrode 108 can comprise a connecting structure 118 and a contact element 116 as described herein. The connecting structure 118 can be formed as a wire mesh 124 that is soldered centrally onto the current output-side end face 112 of the base body. The contact element 116 can be designed as a retaining plate that is clamped onto the wire mesh 124 in a cross or star shape, for example. The retaining plate 136 can be clamped all the way around the support ring 132 arranged on the current output side. Alternatively, the contact element 116 or the retaining plate 136 can also be soldered directly onto the connecting structure 118, designed as a wire mesh 124. Contacting or energizing the second electrode 108 can be done via a connection contact 134, which is held by means of the holding plate 136. The connection contact 134 can be designed as a pin or a welded nut welded onto the contact element 116 or onto the holding plate 134, as described herein.

By arranging the first electrode 106 and the second electrode 108 in this way, when the electrodes 106, 108 are energized, a potential difference between the first electrode 106 and the second electrode 108 can be formed essentially through the entire base body 102 and thus the base body 102 can be warmed or heated up. The first electrode 106 and the second electrode 108 can be designed according to one of the embodiments described herein. The base body 102 is fixed in the housing 126 by at least one bearing mat 128. In addition to the at least one bearing mat 128, the base body 102 can be mounted in the housing 126 via support rings 132.

5 shows a perspective view of an embodiment of an electrically heatable cleaning unit 100 with two bearing mats 128, 129. In particular, the manufacturability of the contacting of the first electrode 106, for example, arranged on a peripheral surface 104 of the base body 102, is challenging due to the necessary insulation against the housing 126 (not shown), since the housing 126 or the canning can be exposed to high temperatures, accelerations and exhaust gas pressures. The first electrode 106 is arranged in a recess of a first bearing mat 128. The first bearing mat 128 is flush with the first electrode 106 or with an outer surface of the contact element 116 of the first electrode 106. A second bearing mat 129 is arranged on the first bearing mat 128. A recess 138 is provided in the second bearing mat 129 for contacting the first electrode 106. The recess 138 of the second bearing mat 129 can expose an area of the outer surface of the contact element 116 of the first electrode 106 in such a way that this area is accessible from the outside through the housing 126. The electrode 106 can therefore be contacted and energized from the outside through the housing 126. Instead of the first electrode 106 described here, the contacting of a plurality of electrodes 106, 108, in particular also the contacting of the second electrode 108, can also be made possible by a corresponding recess 138 of the bearing mat 129.

An electrical connection of the electrodes 106, 108 via a recess 138 in the second bearing mat 129 and a recess in the housing 126 can be made in various ways. 6 shows a schematic sectional view of an embodiment of an electrically heatable cleaning unit 100 according to 3 with contact via a sleeve 140. The electrode 106, which comprises at least one electrically conductive layer 114, an electrically conductive contact element 116 and an electrically conductive, flexible connection structure 118, is arranged in a first bearing mat 128. The first bearing mat 128 is essentially flush with an outer surface of the contact element 116 facing the housing 126. A second bearing mat 129 rests on the first bearing mat 128, the second bearing mat 129 having a recess 138 in the region of a desired contact of the electrode 106. The second bearing mat 129 with the recess 138 can provide the necessary insulation from the housing 126 and enable the contact of the contact element 116 from the outside. However, the recess 138 on the second bearing mat 129 for contacting the contact element 116 can accommodate the use of axial support rings 132 (see 4 ) necessary.

The contacting of the electrode 106 or the contact element 116 can be done via a sleeve 140 welded into the contact element 116. The sleeve 140 is connected to the contact element 116 of the electrode 106 in an electrically conductive manner. One end of the sleeve 140 is essentially flush with the contact element 116. As in 6 As shown, a slight overhang of the sleeve 140 beyond the contact element 116 is possible, but only to the extent that the sleeve 140 does not extend to the housing 126. Another end of the sleeve 140 extends through the connecting structure 118 in the direction of the base body 102 in order not to hinder the introduction of the electrically heatable cleaning unit 100 into the housing 126, i.e. the canning. The other end of the sleeve 140 can extend into a base body bore 142 of the base body 102, wherein the base body bore 142 has a larger diameter than a diameter of the sleeve 140. In order to avoid, for example, a problem of thermal expansion of the base body 102 or the sleeve 140, an air gap is formed between the sleeve 140 and the base body 102 through the base body bore 142 and through an end of the sleeve 140 protruding into the base body bore 142, so that the sleeve 140 and the base body 102 do not touch.

In order to counteract slipping of the flexible connection structure 118 and/or the contact element 116 during canning, firmly connected, stable elements, for example the contact fixings 120, 121 of the electrically heatable unit 100 described herein, are also advantageous. In particular, the connection of the connection structure 118 to the electrically conductive layer 114 and the contact element 116 by means of a first contact fixing 120 and a second contact fixing 121 described herein can be advantageous (not shown) in order to prevent the contact from shifting during the canning process. elements 116. This enables fully automated canning.

After canning, a pin 144 can be introduced into the sleeve 140 via or through the recess 138. The sleeve 140 can, for example, have an internal thread into which the pin 144 can be screwed. The pin 144 can have a socket 146 for insulation against the housing 126. The socket 146 can be made of an electrically insulating material. Alternatively, the socket 146 can also be made of an electrically conductive material and shrunk onto the pin 144. In this embodiment, the pin 144 is ceramically coated in an area in which the pin 144 is enveloped by the socket 146, so that the pin 144 and the socket 146 are connected to one another in an electrically insulating manner. The socket 146 is arranged at a distance from the contact element 116. The socket 146 can be attached to the housing 126 in a gas-tight manner after canning, for example by welding. The pin 144 can be electrically connected to a control unit (not shown). The control unit can control the formation of a potential difference between at least two electrodes 106, 108 as required.

7 shows a schematic sectional view of another embodiment of an electrically heatable cleaning unit 100 according to 3 with contact via a welded-on pin 144. The contact element 116 can also be contacted via an electrically conductive pin 144 welded onto the contact element 116. After canning, the pin 144 is electrically conductively connected to the contact element 116 through the recess 138 of the bearing mat 129, for example by resistance welding or friction welding. A recess in the housing 126 and the recess 138 in the bearing mat 129 are dimensioned such that the pin 144 can be guided through the recess in the housing 126 and through the recess 138 in the bearing mat 129 and can be attached to the contact element 116. The pin 144 extends in the direction away from the base body 102 out of the housing 126. The pin 144 can have an electrically insulating socket 146 to insulate the pin 144 from the metallic housing 126. The socket 146 can be pre-mounted on the pin 144 or can be subsequently plugged onto the pin 144 after the pin 144 has been attached to the contact element 116, so that the socket 146 is arranged between the pin 144 and the housing 126. The socket 146 can also, as in the embodiment of the 6 described, be made of an electrically conductive material, wherein the socket 146 and the pin 144 are connected to one another in an electrically insulating manner. The socket 146 can be attached to the housing 126 in a gas-tight manner, for example by welding. Alternatively or optionally, the socket 146 can also be arranged on a hat plate 148. Using the hat plate 148 can be advantageous if the pin 144 is not positioned precisely during canning or if the sockets 146 are not round. The socket 146 can then be pushed onto the pin 144 together or separately with the hat plate 148. The hat plate 148 is then attached to the housing 126 in a gas-tight manner, for example by welding using a circular seam, in order to close the recess in the housing 126.

List of reference symbols

100

electrically heated cleaning unit

102

Base body

103

Honeycomb structure

104

Circumferential area

106

electrode

108

electrode

110

current input side face

112

current output side face

114

layer

116

Contact element

118

Connection structure

120

Contact fixation

121

Contact fixation

122

Plumb points

124

Wire mesh

126

Housing

128

Storage mat

129

Storage mat

130

Flow direction

132

Support ring

134

Connection contact

136

Retaining plate

138

Recess

140

Sleeve

142

Base body bore

144

Pin code

146

Rifle

148

Hat plate

A

Axis of symmetry

E

Cutting plane

Claims (21)

Electrically heatable unit (100) for use in a gas flow, in particular for an exhaust gas aftertreatment device of an internal combustion engine, comprising: a base body (102) through which the gas flow can flow and which is electrically conductive, in particular a catalyst substrate, with an end face (110) on the current input side, with an end face (112) on the current output side and with a peripheral surface (104) arranged between the end faces (110, 112); a heating device with at least one first electrode (106) and with at least one second electrode (108), wherein at least one of the electrodes (106, 108), in particular both electrodes (106, 108), comprises: an electrically conductive layer (114) which is arranged on an outer surface of the base body (102) or applied to it and which is electrically conductively connected to the base body (102); an electrically conductive contact element (116) arranged at a distance from the electrically conductive layer (114); and an electrically conductive, flexible connection structure (118) which is arranged between the electrically conductive layer (114) and the electrically conductive contact element (116) and contacts both the electrically conductive layer (114) and the electrically conductive contact element (116). Electrically heated unit (100) according to Claim 1 , further comprising: at least one first contact fixing (120) which fixes at least one first contact of the electrically conductive layer (114) and the connecting structure (118); and at least one second contact fixing (121) which fixes at least one second contact of the connecting structure (118) and the contact element (116). Electrically heated unit (100) according to Claim 2 , wherein the first contact fixation (120) and/or the second contact fixation (121) are formed at least in sections as a solder layer and/or comprise solder points (122). Electrically heatable unit (100) according to one of the preceding claims, wherein the electrically conductive layer (114) has a layer thickness between 10 µm and 100 µm, in particular between 30 µm and 80 µm, preferably between 40 µm and 60 µm, for example 50 µm +/- 5 µm. Electrically heatable unit (100) according to one of the preceding claims, wherein the electrically conductive layer (114) extends substantially over an entire axial length in the axial direction of the base body (102). Electrically heatable unit (100) according to one of the preceding claims, wherein two or more first electrodes (106) and/or two or more second electrodes (108) are provided. Electrically heatable unit (100) according to one of the preceding claims, wherein at least one first electrode (106) is arranged on a circumferential surface (104) of the base body (102), in particular wherein the at least one first electrode (106) is closed in the circumferential direction, and/or wherein at least one second electrode (108) is arranged on the circumferential surface (104) of the base body (102), in particular wherein the at least one second electrode (108) is closed in the circumferential direction. Electrically heatable unit (100) according to one of the preceding claims, wherein at least one first electrode (106) is arranged on an end face (110, 112) of the base body (102) and/or wherein at least one second electrode (108) is arranged on an end face (110, 112) of the base body (102). Electrically heatable unit (100) according to one of the preceding claims, wherein the electrically conductive contact element (116) is a sheet metal component which is curved or flat at least in sections. Electrically heatable unit (100) according to one of the preceding claims, wherein the electrically conductive contact element (116) is made of a temperature-stable and/or corrosion-resistant material, in particular of stainless steel. Electrically heatable unit (100) according to one of the preceding claims, wherein the electrically conductive, flexible connecting structure (118) has an irregular structure, in particular wherein the connecting structure (118) comprises a wire mesh (124). Electrically heatable unit (100) according to at least one of the Claims 1 until 10 , wherein the electrically conductive, flexible connection structure (118) has a regular structure, in particular wherein the structure has a plurality of discrete connection elements which are preferably prestressed in the radial direction. Electrically heatable unit (100) according to one of the preceding claims, further comprising: a sleeve (140) with an internal thread, wherein the sleeve (140) is electrically conductively connected to the contact element (116) and extends in the direction of the base body (102). Electrically heated unit (100) according to Claim 13 wherein one end of the sleeve (140) is substantially flush with the contact element (116). Electrically heatable unit (100) according to at least one of the Claims 13 or 14 , wherein one end of the sleeve (140) extends into a base body bore (142) of the base body (102), wherein the base body bore (142) has a larger diameter than a diameter of the sleeve (140). Electrically heatable unit (100) according to at least one of the Claims 1 until 12 , further comprising: a pin (144) which is electrically conductively connected to the contact element (116), wherein the pin (144) extends in the direction away from the base body (102). Electrically heatable unit (100) according to one of the preceding claims, wherein the electrically heatable unit (100) is clamped in a housing (126). Electrically heated unit (100) according to Claim 17 , wherein at least one bearing mat (128, 129) is arranged between the housing (126) and the base body (102), in particular between the housing (126) and the contact element (116). Electrically heated unit (100) according to Claim 17 , wherein two or more bearing mats (128, 129) are arranged between the housing (126) and the base body (102), wherein at least one bearing mat (129) is arranged between the housing (126) and the contact element (116). Exhaust system comprising an exhaust aftertreatment device with an electrically heatable unit (100) according to at least one of the preceding claims. Vehicle with an internal combustion engine equipped with an exhaust system in accordance with Claim 20 connected is.

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