Electrical feedthrough with contact protection

Abstract

The invention relates to an electrical feedthrough (1) for electrically contacting and connecting to a heating conductor in an exhaust gas guiding device for heating an exhaust gas flow, the heating conductor being arranged in a housing (2), at least one electrical conductor (4) formed as a pin being guided through an opening (3) in the housing (2) and being electrically conductively connected to the heating conductor, the electrical conductor (4) being electrically insulated with respect to the housing (2) and being permanently connected to the housing (2) by means of a frame (6), the section (7) of the electrical conductor (4) lying outside the housing (2) being surrounded by a contact protection (11, 20, 31).

Description

[Technical Field]

[0001] The present invention relates to an electrical feedthrough for electrically contacting and connecting a heating conductor in an exhaust gas guiding device for heating an exhaust gas flow, wherein the heating conductor is arranged in a housing, and at least one electrical conductor formed as a pin is guided through an opening in the housing and is electrically connected to the heating conductor, the electrical conductor being electrically insulated from the housing and permanently connected to the housing by means of a frame. [Background technology]

[0002] In particular, in the exhaust gas systems of internal combustion engines, heating elements are used to heat devices for exhaust gas aftertreatment more quickly. These heating elements heat both the flowing exhaust gas and adjacently arranged structures, such as a honeycomb body forming a catalyst or an evaporation element. Preferably, heating is performed using ohmic resistance, whereby an electric current is converted into heat in the electrically conductive structure. Various types of heating elements of this type are known in the prior art. These heating elements include, for example, a metallic honeycomb body that is arranged in a housing and through which the exhaust gas can flow. The honeycomb body is electrically conductively connected to a voltage source using an electrical feedthrough that passes through the housing.

[0003] The challenge for such heating elements is, on the one hand, the durability of the electrical connection of the honeycomb body, which must take into account the mechanical loads, thermal loads, and corrosion effects that occur in automobiles. Furthermore, it must be ensured that full electrical insulation is achieved at predefined locations to ensure a controlled current flow from the voltage source to the honeycomb body. A short circuit resulting from defective electrical insulation can lead to undesired electrical conduction through the honeycomb body and, in some cases, contribute to the destruction of the honeycomb body. Undesired short circuits can also pose a risk to personnel. Processes that can lead to undesired short circuits are, in particular, assembly processes, repair work on the vehicle, or accidents.

[0004] In particular, electrical contacts on the outside of the housing of the heating element are exposed to particularly strong external influences due to the positioning of the electrical contacts on the underside of the vehicle or in the immediate vicinity of the engine, and are typically loaded with dust, dirt, water or corrosive media, such as salt water, during operation, which can permanently damage the electrical contacts.

[0005] A particular disadvantage of prior art devices is that the above-mentioned external influences can lead to a permanent breakdown of the electrical insulation or to a sufficiently conductive medium, such as salt water, which can electrically connect two sections that are essentially electrically isolated from one another. In addition to providing materials that are sufficiently mechanically robust, robustness, especially against electrochemical influences, must also be ensured. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is therefore to provide an electrical feedthrough for contacting a heatable honeycomb body, which has contact protection and protection against fluids, thereby avoiding undesirable short circuits and leakage currents as well as breakdown of the electrical insulation. [Means for solving the problem]

[0007] The problem with electrical feedthroughs is solved by an electrical feedthrough having the features of claim 1.

[0008] One embodiment of the present invention relates to an electrical feedthrough for electrically contacting and connecting to a heating conductor in an exhaust gas guiding device for heating an exhaust gas flow, wherein the heating conductor is arranged in a housing, at least one electrical conductor formed as a pin is guided through an opening in the housing and is electrically connected to the heating conductor, the electrical conductor being electrically insulated from the housing and permanently connected to the housing by means of a frame, wherein the section of the electrical conductor that is outside the housing is surrounded by a contact protection part.

[0009] Electrical feedthroughs are used, for example, to electrically contact and connect a heated catalytic converter in an exhaust gas system of a motor vehicle. The electrical conductors introduced into the exhaust gas system, which is spatially limited by the housing, are electrically insulated from the housing by suitable insulation. For this purpose, for example, a ceramic insulating sleeve is used to accommodate the electrical conductors. The ceramic insulating sleeve itself is accommodated in a similar metal sleeve, which is durably connected to the housing.

[0010] The heating catalyst is preferably formed by a metallic honeycomb body that can be passed by an electric current along a defined path, for which purpose the metallic honeycomb body is brought into conductive contact with an electrical conductor.

[0011] Contact protection arranged on the outer region of the electrical feedthrough can reduce or completely prevent direct mechanical damage, and also reduce the potential for conductive liquids to be loaded. The design of the contact protection, and in particular the material selection, is particularly important here. By reducing the loading of corrosive media on the electrical insulation, damage to the ceramic forming the insulation can be avoided, for example by avoiding cleaning.

[0012] In particular, the contact protection acts against unintentional contact with the electrical conductor, in particular by a hand or a conductive foreign object. The contact protection is used here, in particular, to shield the electrical conductor, the housing portion into which the electrical conductor is inserted, and the connection between the electrical conductor and the electrical line that supplies the current. Another important task of the contact protection is to keep all kinds of fluids, in particular conductive liquids, away from the electrical conductor or, in particular, from the insulating portion that electrically insulates the electrical conductor from the metal sleeve and the housing. Therefore, the concept of contact protection is not limited to physical contact protection to prevent short circuits, but also refers to preventing fluids, in particular corrosive and / or conductive fluids, from coming into contact with the electrical conductor.

[0013] It is particularly advantageous if the housing has a collar protruding from the housing and surrounding the opening in the housing. The collar can be formed, for example, by a metal ring connected to the housing. The collar is preferably formed to extend completely around the circumference of the electrical conductor. Preferably, the collar starts from the outer wall of the housing and extends away from the housing, thus forming a substantially cylindrical interior chamber in which the section of the electrical conductor located outside the housing is accommodated.

[0014] In a preferred embodiment, the collar projects from the housing until the area of ​​the electrical conductor located outside the housing is completely surrounded by the collar. The end of the collar facing away from the housing is open, preferably forming an annular gap with the electrical conductor. This annular gap is preferably designed to prevent the ingress of foreign matter and is also designed sufficiently narrow that it is impossible to penetrate the area between the electrical conductor and the collar.

[0015] In another configuration, the collar is configured such that the electrical conductor protrudes beyond the collar, the protruding area of ​​the electrical conductor preferably being electrically insulating.

[0016] It is also advantageous if the collar tapers conically along its extension length in the direction away from the housing, in order to form a sufficiently narrow annular gap, particularly at the open end of the collar.

[0017] In alternative embodiments, the collar may be cylindrical or, for example, stepped. The collar preferably has heat-dissipating elements, such as ribs, to allow heat generated in the housing, and particularly in the contact area between the electrical conductor and the metal honeycomb body, to be dissipated. Suitable materials for the collar include high-temperature-resistant plastic, ceramic, or aluminum.

[0018] The collar may be durably welded to the housing or may be coupled with a clip or via a threaded fastener for replacement or maintenance purposes. Additionally, the collar may have an opening configured to allow fluid to escape while preventing the ingress of foreign matter.

[0019] A preferred embodiment is characterized in that the electrical conductor is connected to the current-guiding line on the outside of the housing by means of a connecting element, and the collar protrudes at least partially beyond the connecting element.

[0020] The electrical conductor, formed as a metal pin, is connected to the electrical supply line using a connecting element, for example, a screwable clamp. In this case, the connecting element can completely accommodate the outwardly facing end region of the electrical conductor, so that the electrical conductor is completely surrounded and external contact with the electrical conductor is no longer possible. Therefore, the collar is preferably fitted so that the connecting element extends into the collar. This completely protects the electrical conductor from external contact.

[0021] It is also preferred if the contact protection is formed by a lid-like cover element that is placed over the outer region of the electrical conductor. As an alternative to or in addition to the collar, the contact protection can also be formed by a lid-like cover element that is placed over the region of the electrical conductor that is located outside the housing to prevent undesired contact with the electrical conductor. The lid-like element is preferably formed so that a minimum distance is formed between the electrical conductor and the lid-like element at all points. Alternatively, an electrically insulating intermediate layer can be provided at narrow points or contact points to ensure that the contact protection does not have an electrical potential.

[0022] Insofar as the cover element described as the contact protection is provided to substantially prevent the ingress of fluids into the insulating part, this cover element may be electrically conductively connected to an electrical conductor, and in this case, the cover element must be supported in such a way that an electrical short circuit with the housing cannot occur.

[0023] Furthermore, it is advantageous if the lid-like element projects into or surrounds a collar projecting from the housing. The lid-like element may have an outer diameter smaller than the inner diameter of the collar, so that the lid-like element can engage within the collar. Similarly, an inverse relationship of diameters is also possible, in which case the lid-like element surrounds the collar. Both the lid-like element and the collar may have a stepped passage that forms an area extending substantially parallel to the housing surface. This allows a labyrinth-like structure to be formed between the collar and the lid-like element, which is particularly effective in preventing the ingress and penetration of foreign objects.

[0024] It is furthermore advantageous if the housing is associated with a first potential, the electrical conductor with a second potential, and the contact protection is not associated with a potential, if this is advantageous or necessary to prevent contact with the contact protection from causing a short circuit and creating a risk to the environment.

[0025] It is also advantageous if the contact protection is made of a metal grid, perforated sheet metal or expanded metal, which has the advantage that it can be easily shaped, provides good protection against foreign matter and still allows fluids to escape and not accumulate on electrical conductors or, for example, electrical insulation.

[0026] Furthermore, it is advantageous if the contact protection is configured to be electrically insulating with respect to the electrical conductors and / or current-carrying lines and / or the housing. For this purpose, for example, rubber elements or silicone seals can be used. Electrical insulation is particularly advantageous for preventing short circuits.

[0027] Furthermore, it is advantageous if the open area of ​​the contact protection facing the housing is closed. This helps in particular to resist the ingress of foreign matter or unwanted intervention. In a preferred configuration, the contact protection, or the insulating means arranged in the open area, has at least a small opening that allows the outflow of fluid in the base area of ​​the contact protection near the housing.

[0028] Advantageous refinements of the invention are set forth in the dependent claims and in the following description of the drawings.

[0029] The invention will now be described in detail with reference to several exemplary embodiments with reference to the drawings. [Brief explanation of the drawings]

[0030] [Figure 1] 3 shows a cross-sectional view of an electrical feedthrough, in which the area outside the electrical conductor is surrounded by a contact protection portion. [Figure 2] 1 is a cross-sectional view of an electrical feedthrough with a lid-like cover placed over the electrical conductors. [Figure 3] 2 is a cross-sectional view with the contact protection shown in FIG. 1, where an insulating means is additionally provided between the electrical conductor and the contact protection. [Figure 4] FIG. 1 is a perspective view of an electrical feedthrough with a collar protruding from a housing. [Figure 5] 10 is a schematic diagram showing a lid-like cover engaging with a collar, thereby forming a labyrinth-like structure. FIG. [Figure 6] 10A-10C show three different embodiments of a collar that can protrude from the housing. [Figure 7] 1 shows a perspective cross-sectional view of an electrical feed-through, in which a collar is guided from a housing to a centering sleeve of a connecting element used for electrical contacting. [Figure 8]1 is a cross-sectional view of an electrical feedthrough in which a cover element is placed over an electrical conductor, thereby forming an air gap between the cover element and a metal sleeve. DETAILED DESCRIPTION OF THE INVENTION

[0031] Figure 1 shows an electrical feedthrough 1. The housing 2 has an opening 3 through which an electrical conductor 4 formed by a metal pin is guided. The conductor 4 is surrounded by a sleeve-like insulation 5 housed in a metal sleeve 6. The metal sleeve 6 is itself welded to the housing 2.

[0032] The electrical conductor 4 projects in its axial extension beyond the metal sleeve 6 and the insulation 5, thus forming a region 7 located outside the housing 2. In this region 7, the electrical conductor 4 is connected by a connecting element 8 to an electrical supply line 9, so that the electrical conductor 4 is associated with a first voltage potential. The housing 2 is typically associated with a second voltage potential.

[0033] 1 shows the heat transport from the electrical conductors 4 to the surroundings, which carries heat away from the interior of the housing 2. The heat transport must not be completely blocked or substantially impeded, in particular by contact protection 11 as shown in FIG.

[0034] The contact protection 11 surrounds the outer region 7 of the electrical conductor 4, the connecting element 8 and part of the electrical supply line 9. The contact protection 11 is preferably mounted on the insulating part 5, so that it is not electrically connected to the electrical conductor 4. Insulating elements 12 may additionally be provided at the points of contact with the insulating part 5 or the electrical conductor 4, preventing current from being introduced into the contact protection 11. Insulating elements 12 may also be provided on the electrical supply line 9 to electrically isolate the contact protection 11.

[0035] Figure 2 shows a cross section of an electrical feedthrough 1 as already shown in Figure 1. The reference numbers for identical elements in Figure 2 and in the subsequent figures correspond to the reference numbers shown in Figure 1.

[0036] 2, a lid-like cover element is provided as the contact protection 20, which is pressed onto the electrical conductor 4 and lowered onto the housing 2 or the insulating part 5 or the metal sleeve 6. Preferably, this contact protection 20 is not electrically conductive and therefore acts as an electrical insulator, which makes it unnecessary to provide a separate insulating means.

[0037] 2 also provides protection against the ingress of corrosive media into the insulation 5, thereby preventing, in particular, galvanic corrosion and thus the insidious destruction of the insulation 5. This also makes it possible to avoid periodic cleaning of the insulation 5, which is made of oxide ceramic.

[0038] The contact protection 20 shown in FIG. 2 can be particularly advantageously combined with the contact protection 11 shown in FIG. 1, so that protection against unwanted contact of the electrical conductor 4 and all current-carrying elements is achieved to the same extent as protection against the ingress of fluids and corrosive media into the insulating part 5.

[0039] FIG. 3 shows a cross section of the electrical feedthrough 1 of FIGS.

[0040] The electrical conductor 4 has insulating means 30 at its axial end, which separate the electrical conductor 4 from the contact protection 31. Furthermore, insulating means 32 are provided which separate the contact protection 31 from the metal sleeve 6, and insulating means 33 which provide insulation for the electrical supply line 9. In this case, the insulating means 32 closes the open area of ​​the contact protection 31 facing the housing 2.

[0041] The contact protection 31 is configured to physically prevent unwanted contact with the electrical conductor 4 by being made of a sufficiently rigid material that can withstand external forces, so that deformation that would lead to contact between the electrical conductor 4 and the contact protection 31 cannot occur. The contact protection 31 can preferably be made from expanded metal, perforated sheet metal or a mesh metal structure. Alternatively, non-conductive materials could also be considered, which would facilitate electrical insulation.

[0042] The contact protection portion 31 and / or the insulating means 32 preferably have openings that are finely designed to allow the outflow of fluid while effectively preventing the ingress of foreign matter.

[0043] Figure 4 shows a perspective cross-sectional view of the electrical feed-through 1 shown in the preceding figures. In addition to the elements described above, namely the housing 2, the electrical conductor 4, the insulation 5, the metal sleeve 6 and the connecting element 8, Figure 4 shows a collar 40 protruding from the housing 2. In the embodiment of Figure 4, the collar 40 is configured to be conically tapered, and therefore gradually narrows in the direction from the housing 2 towards the axial end region of the electrical conductor 4.

[0044] Preferably, a circumferentially extending annular gap of at least 1.5 mm wide remains between the electrical conductor 4 or connecting element 8 and the collar 40 to avoid electrical contact and at the same time prevent the ingress of foreign matter.

[0045] The collar 40 may have a cylindrical shape or may be formed, for example, stepped. It may be provided with correspondingly dimensioned openings that allow the fluid to escape. Preferably, the collar 40 is formed from a metallic material that matches, for example, the material of the housing 2. High-temperature resistant plastics or ceramics are also conceivable.

[0046] The height of the collar 40 can vary and, for example, can also encompass different parts of the connecting element 8. Furthermore, additional electrically insulating elements can be provided.

[0047] It is particularly advantageous to combine the collar 40 with one of the contact protection parts 11, 20, 31. The contact protection part can engage within or surround the collar 40 and thus form an effective protection against unwanted contact.

[0048] Figure 5 shows a cross section of a lid-like contact protection, for example as shown at 20 in Figure 2, which projects into a collar 40. Between the two elements 20, 40, insulating means can be provided.

[0049] FIG. 6 shows three perspective views of a collar 50 that may protrude from a housing not shown in FIG. 6 and surround at least a portion of an electrical conductor.

[0050] The left part of the drawing shows a conically tapered collar 50 which has a flattened upper edge and which has outlet slits 51 in the base region 4, which are preferably arranged circumferentially offset by 90 degrees from one another.

[0051] The outflow slit has a height of about 2 mm in the illustrated configuration of the collar 50 when used in an automobile.

[0052] The middle variation shows a collar 50. This collar 50 has two outflow slits 52 spaced 180 degrees apart in the circumferential direction, and these outflow slits 52 have a height of 4 mm. At the upper end of the collar 50, a dripping edge 53 is formed to extend annularly in the circumferential direction, and this dripping edge 53 is particularly desirable to prevent fluid from entering a gap formed between the collar 50 and an electrical feedthrough (not shown).

[0053] The variant on the right shows a collar 50 without an outflow slit and with the already shown drip edge 53 in the middle. The various features of the collar 50 shown in Figure 6 can be combined with one another in any way.

[0054] FIG. 7 shows a perspective view of the electrical feedthrough 1 as already shown in FIG. 4, with the collar 60 now being guided clearly beyond the lower end of the connecting element 8 .

[0055] The centering sleeve, designated by the reference numeral 61, is configured as an annular element with an L-shaped cross section and serves to center the electrical conductor 4 within the collar 60. After assembly, the centering sleeve 61 is removed, leaving a circumferentially extending annular gap between the collar 60 and the connecting element 8.

[0056] Factors that optimize the ingress of fluid into the collar 60 are, in particular, the width of the circumferentially extending gap, on the one hand, and the length of the axial overlap between the collar 60 and the connecting element 8, on the other hand.

[0057] FIG. 8 shows a cross section of the electrical feedthrough 1, with a lid-like cover 70 pressed onto the electrical conductor 4, which may for example be part of the connecting element 8.

[0058] Between the cover 70 and the metal sleeve 6, a gap 71 is formed, which has the radial width of the metal sleeve 6. Furthermore, there is an axial overlap between the metal sleeve 6 and the cover 70. By adapting the cover 70, the width of the gap 71 and the length of the overlap can be adapted. A gap width of 2 mm or less has proven to be particularly advantageous for preventing fluids from entering and thus loading the insulation 5.

[0059] The length of the overlap is preferably at least 5 mm, which has likewise been found to be particularly advantageous in order to prevent or significantly reduce the ingress of fluids.

[0060] The various features of the individual embodiments may also be combined with one another as described above or in a similar manner.

[0061] The embodiments shown in FIGS. 1 to 8 do not have any particular limiting features, but are merely used to clarify the discussion of the present invention. [Explanation of symbols]

[0062] 1 Electrical Feedthrough 2. Housing 3 aperture 4 Electrical conductor 5 Insulation 6 Metal sleeve 7. The area outside an electrical conductor 8 Connecting Elements 9 Electrical supply lines 10 Arrows Heat transport 11 Contact protection 12 Electrically insulating elements 20 Contact protection part 30 Electrically insulating elements 31 Contact protection part 32 Electrical insulating elements 33 Electrically insulating elements 40 colors 50 colors 51 Outlet slit 52 Outlet slit 53 Dripping edge 60 colors 61 Centering sleeve 70 Cover Elements 71 void

Claims

[Claim 1] 1. An electrical feedthrough (1) for electrically contacting and connecting a heating conductor in an exhaust gas guiding device for heating an exhaust gas flow, the heating conductor being arranged in a housing (2), at least one electrical conductor (4) formed as a pin being guided through an opening (3) in the housing (2) and being electrically connected to the heating conductor, the electrical conductor (4) being electrically insulated from the housing (2) and being permanently connected to the housing (2) by means of a metal sleeve (6). The electrical conductor (4) is connected to a current-carrying line (9) on the outside of the housing (2) by means of a connecting element (8), A lid-like cover (70) that is part of the connecting element (8) is pressed onto the section (7) of the electrical conductor (4) that is located outside the housing (2), An electrical feedthrough (1), characterized in that between the cover (70) and the metal sleeve (6) there is a gap (71) having a radial width of the metal sleeve (6).

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