Device for the electrical contacting of a heating conductor

Abstract

The invention relates to a device for electrical contacting of a heating conductor in a exhaust gas line, wherein the heating conductor is arranged within a metal housing and at least one electrical conductor is passed through this housing in order to contact the heating conductor inside, with an insulating means (3) which is designed as a sleeve, wherein the sleeve has a central bore, through which the electrical conductor (2) is passed, wherein the insulating means (3) has a first metallised zone (4) on its radially outwardly directed surface, to which a first metal sleeve (7) is permanently connected and the insulating means (3) further has a second metallised zone (5) on its radially outwardly directed surface, to which a second metal sleeve (8) is permanently connected.

Description

[0001] Description

[0002] Device for electrically contacting a heating conductor

[0003] Technical area

[0004] The invention relates to a device for electrically contacting a heating conductor in an exhaust gas line, wherein the heating conductor is arranged within a metallic housing and at least one electrical conductor is guided through this housing in order to contact the heating conductor in the interior, with an insulating means which is designed as a sleeve, wherein the sleeve has a central bore through which the electrical conductor is guided.

[0005] State of the art

[0006] Electric heating elements are now routinely used to heat exhaust gases in an exhaust system downstream of a combustion engine or the exhaust gas flowing through an exhaust system. The goal here is to more quickly reach a temperature threshold at which effective conversion of the pollutants carried in the exhaust can occur. This is necessary because the catalytically active surfaces of the catalysts installed in the exhaust system used for exhaust gas aftertreatment only allow sufficient conversion of the respective pollutants above a minimum temperature, the so-called light-off temperature.

[0007] Known solutions in the prior art include so-called heating catalysts, which have a metallic structure connected to a voltage source or a metallically coated ceramic structure which can be heated by utilizing the ohmic resistance.

[0008] To electrically connect the heatable structure, an electrical conductor must be inserted at least once through the housing of the exhaust system or a catalytic converter located in the exhaust system. It must be ensured that the feedthrough is gas-tight, that there is electrical insulation between the housing and the electrical conductor, and that sufficient durability is guaranteed. The electrical conductor is usually made of a solid, solid material, such as a metal bolt.

[0009] DE 10 2012 110 098 B4 discloses a method for producing an electrical feedthrough for the power supply of an electric exhaust gas heater in a motor vehicle. The feedthrough has an outer tube, the interior of which is penetrated by an electrical conductor. The electrical conductor projects beyond the outer tube on at least one end face of the outer tube. The electrical conductor is surrounded by an insulating material in the interior of the outer tube. The feedthrough is produced by cutting a compacted rod material to length, with regions of the section acting as the outer tube and the section acting as the insulating material being removed by machining processes in order to produce an electrical feedthrough of the desired length with a desired projection of the electrical conductor beyond the outer tube.

[0010] A particular disadvantage of the prior art methods for producing electrical feedthroughs is that the compacted bar stock used is very expensive due to its multi-layer structure. Furthermore, a significant portion of approximately two-thirds of the bar stock is destroyed during machining to expose the electrical conductor and cut the electrical feedthrough to length, resulting in unused material being wasted. This makes the manufacturing process particularly complex and costly.

[0011] Furthermore, the known prior-art solutions are often characterized by poor gas-tightness and low resistance to moisture. Electrical corrosion also occurs, particularly in applications with 48-volt operating voltage, which negatively impacts durability. Description of the invention, problem, solution, advantages

[0012] Therefore, the object of the present invention is to provide a device which enables improved electrical contacting of the heating conductor inside the housing and is thereby improved with regard to gas tightness and corrosion resistance.

[0013] The object with regard to the device is achieved by a device having the features of claim 1.

[0014] One embodiment of the invention relates to a device for electrically contacting a heating conductor in an exhaust gas path, wherein the heating conductor is arranged within a metallic housing and at least one electrical conductor is guided through this housing in order to contact the heating conductor in the interior, with an insulating means which is designed as a sleeve, wherein the sleeve has a central bore through which the electrical conductor is guided, wherein the insulating means has a first metallized zone on its radially outwardly directed surface, to which a first metal sleeve is permanently connected, and the insulating means further has a second metallized zone on its radially outwardly directed surface, to which a second metal sleeve is permanently connected.

[0015] The insulation means is preferably formed by a sleeve having a continuous bore along its axial extent. The insulation means thus has an annular cross-section. The bore runs along the central axis of the insulation means, and the insulation means is preferably rotationally symmetrical about its central axis. The axial direction describes the extension along the bore or the central axis, whereas the radial direction describes a normal to the central axis.

[0016] The insulating means is preferably made of an electrically insulating material, such as a ceramic material. The insulating means can be produced, for example, from a powdered oxide ceramic by sintering or pressing.

[0017] The hole is preferably dimensioned so that the electrical conductor, which can also be referred to as the inner conductor, can be inserted precisely into this hole. It is particularly important to note that the electrical conductor is made of a metallic material, preferably 2.4869 steel, and therefore exhibits different expansion behavior under the influence of heat than the insulating material made of a ceramic. The hole must therefore be dimensioned such that the expansion of the electrical conductor does not lead to damage to the insulating material.

[0018] The metallized zones are areas on the outer circumference of the insulation. These are preferably formed completely circumferentially. The insulation can be metallized, for example, by a surface coating, which gives the metallized zone properties similar to a metallic material and, in particular, allows common joining processes for connecting metallic materials to one another.

[0019] Sleeves can be connected to the metallized zones, which are used to connect the insulation to the housing of the device and to connect the electrical conductor to the insulation.

[0020] It is particularly advantageous if the first metallized zone and the second metallized zone are arranged at a distance from one another along the axial extension direction of the insulating means.

[0021] To prevent electrically conductive contact between the two sleeves or between the two electrically conductive metallized zones, these are preferably spaced apart along the axial extent of the insulation. A creepage distance is thus formed between the two metallized zones, which is intended to prevent an electrical short circuit between the sleeves or the metallized zones. The length of this creepage distance depends on the voltages applied to the sleeves. The higher the voltage level, the longer the creepage distance should be.

[0022] It is also advantageous if the first metal sleeve forms the link to the housing of the device. The insulation material is connected to the housing via the first metal sleeve. The first metal sleeve is connected to the metallized zone on the one hand, for example by soldering, and to the housing on the other hand, for example by welding. In principle, all known methods for joining metallic materials can be used; however, care must be taken to ensure that the connection of the metal sleeve to the housing does not damage the connection between the metal sleeve and the insulation material, or vice versa. In particular, if one of the connections is created by soldering, the thermal stress caused by a welding process can damage the soldered connection.

[0023] The metal sleeve is preferably dimensioned such that it rests on the metallized zone of the insulation over a sufficiently large area, while simultaneously forming a sufficiently large contact area with the housing. The electrical conductor routed through the insulation, which, by design, is also routed through the metal sleeve, must be sufficiently spaced with its radially outward-facing surface from the radially inward-facing surface of the metal sleeve to prevent the occurrence of a short circuit.

[0024] A preferred embodiment is characterized in that the second metal sleeve forms the connecting link to the electrical conductor guided through the insulating means.

[0025] The second metal sleeve rests against the second metallized zone and is preferably also soldered to it. The second metal sleeve can then be connected to the electrical conductor by welding. Here, too, it is important to select suitable joining methods in a sensible and coordinated sequence to ensure that thermally unstable connections are not damaged by the heat input from another connection.

[0026] It is also preferable if the first metal sleeve and / or the second metal sleeve are connected to their respective metallized zone by means of a soldering process.

[0027] Furthermore, it is advantageous if the insulating means has a smaller outer diameter in the region of at least one of the metallized zones than in the region of the insulating means which separates the two metallized zones from one another.

[0028] The insulation means can preferably have circumferentially extending shoulders extending from the axial ends to the center of the insulation means. The creepage distance region can in turn have a larger diameter, so that the creepage distance region forms, for example, a stop for the metal sleeves attached from the respective end regions. This would simplify the positioning of the metal sleeves on the one hand, and effectively prevent slipping or even contact between the metal sleeves on the other. Even the destruction of a connection between a metallized zone and a metal sleeve would have no effect on the electrical separation of the two metal sleeves due to the larger diameter of the insulation means in the creepage distance region.

[0029] Furthermore, it is advantageous if the insulating means is formed from a ceramic material, wherein the surface of the insulating means in the region of the metallized zones is processed in such a way that a metallized surface is formed.

[0030] It is also expedient if the second metallized zone with the second metal sleeve is arranged within the housing. Furthermore, it is advantageous if the region of the insulating means that separates the two metallized zones is arranged within the housing.

[0031] In the application according to the invention, the insulation material, with its two metallized zones and the soldered sleeves, is inserted into an opening in the housing. A durable, fluid-tight connection is then created between the metal sleeve and the housing. The area of ​​the insulation material facing away from this first metal sleeve and the second metal sleeve are thus forcibly arranged within the housing.

[0032] This is particularly advantageous because the untreated area of ​​the insulation, which forms the creepage distance, is located inside the housing and is therefore not exposed to corrosive influences, which can originate in particular from the environment.

[0033] Advantageous further developments of the present invention are described in the subclaims and in the following description of the figures.

[0034] Short description of the drawings

[0035] The invention is explained in detail below using an exemplary embodiment with reference to the drawing. The drawing shows:

[0036] Fig. 1 is a sectional view through a device according to the invention.

[0037] Preferred embodiment of the invention

[0038] Figure 1 shows an electrical feedthrough 1, which is formed from an electrical conductor 2 that is guided through an insulating means 3. The electrical conductor 2 is formed by a metallic bolt. The insulating means 3 is formed by an annular sleeve that has a central bore through which the electrical conductor 2 is guided. The insulating means 3 has two zones 4, 5 that have a smaller diameter than the region 6, which spaces the two zones 4, 5 apart and forms a creepage distance that counteracts an electrical short circuit between the two zones 4, 5.

[0039] Zones 4 and 5 are metallized. The metal sleeves 7 and 8 are each pushed onto one of the metallized zones 4 and 5 and permanently connected to them, for example, by soldering.

[0040] The first metal sleeve 7, which is connected to the first metallized zone 4, serves as a connection between the electrical feedthrough and the housing (not shown). The second metal sleeve 8, which is connected to the second metallized zone 5, serves as a connection to the electrical conductor 2.

[0041] In the example of Figure 1, the first metal sleeve 7 is designed as a cylindrical sleeve and rests with its radially inwardly directed surface against the first metallized zone 4. The housing can, for example, be connected to the radially outwardly directed surface of the first metal sleeve 7.

[0042] The second metal sleeve 8 also has a cylindrical portion 9, which is connected to the second metallized zone. Furthermore, the metal sleeve 8 has an angled portion 10, which is angled radially inward and encloses the electrical conductor 2, so that a connection can be created between the electrical conductor and the second metal sleeve 8.

[0043] The electrical conductor 2 has an end region 11 to which the heating conductor (not shown) can be connected inside the housing (not shown). Furthermore, the electrical conductor 2 has a second end region 12 to which an electrical supply line can be connected.

[0044] The embodiment of Figure 1 is not limiting in nature and serves to clarify the inventive concept. List of reference symbols

[0045] 1 . electrical feedthrough

[0046] 2. electrical conductor 3. insulating material

[0047] 4. first metallized zone

[0048] 5. second metallized zone

[0049] 6. Creepage distance

[0050] 7. first metal sleeve 8. second metal sleeve

[0051] 9. cylindrical section

[0052] 10. angled section

[0053] 11 . End area of ​​the electrical conductor

[0054] 12. End area of ​​the electrical conductor

Claims

Patent claims 1. Device for electrically contacting a heating conductor in an exhaust gas path, wherein the heating conductor is arranged within a metallic housing and at least one electrical conductor is guided through this housing in order to contact the heating conductor on the inside, with an insulating means (3) which is designed as a sleeve, wherein the sleeve has a central bore through which the electrical conductor (2) is passed, characterized in that the insulating means (3) has a first metallized zone (4) on its radially outward-facing surface, to which a first metal sleeve (7) is permanently connected, and the insulating means (3) further has a second metallized zone (5) on its radially outward-facing surface, to which a second metal sleeve (8) is permanently connected.

2. Device according to claim 1, characterized in that the first metallized zone (4) and the second metallized zone (5) are arranged at a distance from one another along the axial extension direction of the insulating means (3).

3. Device according to one of the preceding claims, characterized in that the first metal sleeve (7) forms the connecting member to the housing of the device.

4. Device according to one of the preceding claims, characterized in that the second metal sleeve (8) forms the connecting link to the electrical conductor (2) guided through the insulating means (3).

5. Device according to one of the preceding claims, characterized in that the first metal sleeve (7) and / or the second metal sleeve (8) is connected to its respective metallized zone (4, 5) by means of a soldering process. Device according to one of the preceding claims, characterized in that the insulating means (3) has a smaller outer diameter in the region of at least one of the metallized zones (4, 5) than in the region (6) of the insulating means (3) which spaces the two metallized zones (4, 5) apart. Device according to one of the preceding claims, characterized in that the insulating means (3) is formed from a ceramic material, wherein the surface of the insulating means (3) in the region of the metallized zones (4, 5) is machined such that a metallized surface is formed. Device according to one of the preceding claims, characterized in that the second metallized zone (5) with the second metal sleeve (8) is arranged inside the housing.Device according to one of the preceding claims, characterized in that the region (6) of the insulating means (3) which separates the two metallized zones (4, 5) is arranged within the housing.

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