DE102021211207A1 - Electrical feedthrough for electrical contacting of a heating conductor - Google Patents

Abstract

The invention relates to an electrical bushing (1) for making contact through a housing with a heating conductor arranged in a housing, with an inner conductor (2), with an outer conductor (4) and with an electrical insulator (3), the inner conductor (2) is completely surrounded at least in sections in the circumferential direction by the insulator (3) and the insulator (3) and the inner conductor (2) are accommodated in the outer conductor (4) designed as a sleeve, with the electrical feedthrough (1) having an inward opening into the housing directed and an outwardly directed end region (8), the insulator (3) and the outer conductor (4) being covered with a sheet silicate (6) at their end facing the outwardly directed end region (9) of the electrical feedthrough (1). .

Description

technical field

The invention relates to an electrical feedthrough for contacting a heating conductor arranged in a housing through a housing, with an inner conductor, with an outer conductor and with an electrical insulator, the inner conductor being completely surrounded by the insulator at least in sections in the circumferential direction and the insulator and the Inner conductors are accommodated in the outer conductor designed as a sleeve, with the electrical feedthrough having an end region directed inwards into the housing and an end region directed outwards.

State of the art

Heating elements are used to heat up devices for exhaust gas aftertreatment more quickly, in particular in exhaust lines from internal combustion engines. These heat both the flowing exhaust gas and the adjacent structures, such as the honeycomb bodies that form the catalysts, or evaporation elements. Heating preferably takes place using the ohmic resistance, as a result of which an electric current is converted into heat in a conductive structure. Various types of heating elements of this type are known in the prior art. These include, for example, metallic honeycomb bodies, which are arranged within a housing and through which an exhaust gas can flow. The honeycomb bodies are connected in an electrically conductive manner to a voltage source by means of an electrical feedthrough which runs through the housing.

In particular, the electrical contacting outside the housing of the heating element is exposed to particularly strong external influences due to its positioning on the underbody of a motor vehicle or in the direct vicinity of the engine. Typically, such electrical contacts are exposed to dust, dirt, water, corrosive media, such as salt water, during operation, which can lead to permanent damage to the electrical contacts. In particular, moisture can enter the contact area between the inner conductor, the insulator and the outer conductor, which, in the worst case, destroys the insulator, which is usually made of an oxide ceramic, and thus impairs the insulating effect.

A particular disadvantage of the embodiments known from the prior art is that the use of rubber seals is not possible due to the high temperatures and the very limited tree space. The temperatures directly on the exhaust gas line are too high and it is not possible to provide a particularly long electrical feedthrough to get distance to the hot areas due to the tree space restrictions.

Presentation of the invention, task, solution, advantages

It is therefore the object of the present invention to create an electrical feedthrough that has adequate protection for the contact point between the inner conductor, insulator and outer conductor, with the protection being temperature-stable and insensitive to contact with liquid media.

The task with regard to the electrical feedthrough is solved by an electrical feedthrough having the features of claim 1 .

An exemplary embodiment of the invention relates to an electrical feedthrough for contacting a heating conductor arranged in a housing through a housing, with an inner conductor, with an outer conductor and with an electrical insulator, the inner conductor being completely surrounded by the insulator at least in sections in the circumferential direction and the insulator and the inner conductor is accommodated in the outer conductor designed as a sleeve, with the electrical feedthrough having an end region pointing inwards into the housing and an end region pointing outwards, the insulator and the outer conductor at their end facing the end region of the electrical feedthrough pointing outwards are covered with a layered silicate.

The electrical feedthrough is inserted through an opening in a housing, with one end protruding into the housing and the other end protruding from the housing. The part lying on the outside is then connected to an electrical conductor, preferably a cable. The inner conductor thus forms one pole of a voltage source and the outer conductor forms the other pole of the voltage source. In some versions, the pole of the outer conductor is identical to the ground that is present on several components of a motor vehicle. Depending on the voltage level, this is possible without any problems. At higher voltages it is necessary to route the second pole shielded in lines to avoid accidentally touching current-carrying components.

The area of the insulator and the outer conductor protruding from the housing are susceptible to the ingress of liquids, such as water, unless suitable protective measures are provided. Through a contact the insulator, which is usually formed from an oxide ceramic, can be flushed out of the insulator, as a result of which the insulating effect is reduced or completely eliminated. A short circuit can then occur here between the inner conductor and the outer conductor, as a result of which the functionality of the electrically heatable catalytic converter can no longer be guaranteed.

The layered silicate covers the outwardly directed ends of the insulator and the outer conductor and thus protects the insulator from harmful external influences and in particular also from the ingress of fluids into gaps and spaces between the outer conductor, insulator and inner conductor.

It is particularly advantageous if the sheet silicate used is mica. Mica is particularly advantageous because mica has a high temperature resistance, so that the temperatures that usually occur in an exhaust gas aftertreatment system can be withstood without any problems.

Here, mica belongs to a special group of layered silicates, the distinguishing feature of mica being the layered structure and the weak bonding between the individual layers of mica.

Another advantage of mica is that the thermal expansion coefficient of 13.5 ppm/K is closer to the thermal expansion coefficient of the steel components usually used for electrical feedthroughs than the technical ceramics otherwise used, such as Al ₂ O _3' with 6 to 8 ppm/K. K This reduces the occurrence of tension as a result of thermal influences.

In addition, mica is of course electrically insulating and, due to the layer structure, deformable within certain limits, which means that a sealing effect can be produced on the contact surfaces under pressure.

It is also advantageous if the layered silicate is designed as an annular disk with a central opening and the inner conductor protrudes through the central opening. As a result, the layered silicate can be positioned easily and it can be ensured that the layered silicate can be fixed to the electrical feedthrough.

A preferred exemplary embodiment is characterized in that the inner conductor forms a circumferential shoulder on which the layered silicate rests. The surrounding shoulder serves as a support point for the layered silicate. In this way, the layered silicate is easily positioned and a particularly good sealing effect can be achieved by the layered silicate being in contact both on an axial contact surface and on a radial contact surface. In particular, the ingress of water from a radial direction can be prevented particularly well in this way.

It is also preferable if the outwardly directed end of the insulator and the outer conductor lie against the layered silicate lying on the step. The contact of the ends of the insulator and the outer conductor on the layered silicate in conjunction with the axial pressure generated by the fixing agent creates a very good sealing effect, which prevents water or fluids from penetrating the insulator and the outer conductor in general.

In addition, it is advantageous if the layered silicate is fixed in relation to the inner conductor by means of a fixing agent. The fixing agent ensures that the layered silicate remains fixed in place even under the strong mechanical stresses in a motor vehicle. In addition, the fixing agent can advantageously generate a contact pressure on the layered silicate in order to achieve an additional sealing effect.

A nut can be used as a fixing means, for example, which can be screwed onto a thread applied to the inner conductor. It would also be conceivable to provide a latching connection by which the layered silicate is fixed.

Furthermore, it is advantageous if a bushing is arranged on the side of the chic silicate facing the outwardly directed end region, which bushing is pierced through a central opening by the inner conductor and can be fixed by means of the fixing means.

The bushing can advantageously be used as a force transmission means in order to transmit the contact pressure from a nut or another fixing means to the layered silicate.

It is also expedient if the insulator, the outer conductor and the shoulder of the inner conductor terminate flush with one another and form a common support surface for the layered silicate. This is particularly advantageous in order to obtain a flat sealing surface on which the layered silicate can be placed and pressed on by means of contact pressure.

In addition, it is advantageous if the layered silicate has an axial flexibility, with an axially acting force component Compression of the layered silicate is generated, whereby the layered silicate acts as a sealant.

An exemplary embodiment of the invention relates to an electrical feedthrough according to one of the preceding claims, wherein the electrical feedthrough is used in a housing of an exhaust gas line, the layered silicate being arranged on the end region of the electrical feedthrough located outside the housing.

In particular, the area of the electrical feedthrough that is arranged outside the housing is susceptible to damage and the ingress of water or corrosive fluids, which can damage the insulator.

Another advantage of using the solution according to the invention is that an existing electrical feedthrough can easily be retrofitted with a layered silicate as insulation and seal, or an existing electrical feedthrough can easily be adapted to use a layered silicate as a sealant. In addition, the layered silicate can be easily replaced, so that it can be replaced if damage occurs.

Furthermore, it is advantageous that a particularly short overall length of the electrical feedthrough can be achieved through the use of the layered silicate due to the temperature stability, which is particularly advantageous in particular with regard to the installation space restrictions.

Advantageous developments of the present invention are described in the dependent claims and in the following description of the figures.

character list

• 1 eine Schnittansicht durch eine erfindungsgemäße elektrische Durchführung wobei ein Innenleiter, ein Isolator und ein Außenleiter gezeigt sind und ein Schichtsilikat zur Abdichtung am Isolator und Außenleiter angeordnet ist.

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

• 1 a sectional view through an electrical feedthrough according to the invention, an inner conductor, an insulator and an outer conductor being shown and a sheet silicate being arranged for sealing on the insulator and outer conductor.

Preferred embodiment of the invention

The 1 shows a sectional view through an electrical bushing 1. The bushing 1 has an inner conductor 2 designed as a bolt. An insulator 3 is arranged as an annular sleeve around an axial section of the inner conductor 2 . An outer conductor 4, which is also designed as an annular sleeve, accommodates the insulator 3 and the inner conductor 2.

Inner conductor 2, insulator 3 and outer conductor 4 rest against one another and are permanently connected to one another, for example pressed. The inner conductor 2 has a shoulder 5 running around in the circumferential direction, which serves as a bearing seat for the layered silicate 6 designed as an annular disk. The layered silicate 6 is particularly preferably formed by mica, which on the one hand is particularly temperature-stable and on the other hand has a certain flexibility, so that it can be deformed under pressure, such as in particular axial pressure, and can therefore be used as a seal, since it becomes a Any gaps are closed and the mica is pressed with a certain pretension against the contact surface on the outer conductor 4, on the insulator 3 and on the inner conductor 2.

A force is applied to the layered silicate by means of a bushing 7 and a nut 8 in the axial direction and the bearing seat on the shoulder 5 of the inner conductor 2 and the end faces of the insulator 3 and the outer conductor 4 are pressed.

The nut 8 can be screwed onto a thread on the inner conductor 2 , while the socket 7 is slipped over the inner conductor 2 and rests on the layered silicate 6 .

The outer conductor 4 can, for example, be brought into electrically conductive contact with the housing when it is inserted into a housing, so that the housing becomes part of the outer conductor 4 . This can be achieved, for example, by welding the outer conductor 4 into the housing.

The layered silicate 6 is preferably arranged on an area of the electrical feedthrough 1 which is not inside the housing, which is not shown, but outside. The layered silicate 6 thus has an electrically insulating effect between the bushing 7, nut 8, inner conductor 2 and outer conductor 4 and also seals the contact area between the inner conductor 2, insulator 3 and outer conductor 4 against fluids that act on the electrical feedthrough 1 outside the housing can.

The embodiment of 1 has in particular no restrictive character and serves to clarify the idea of the invention.

Reference List

1

electrical implementation

2

inner conductor

3

insulator

4

outer conductor

5

Unit volume

6

layered silicate

7

Rifle

8th

Mother

9

external end area

Claims (10)

Electrical bushing (1) for contacting a heating conductor arranged in a housing through a housing, with an inner conductor (2), with an outer conductor (4) and with an electrical insulator (3), the inner conductor (2) extending at least in sections in the circumferential direction is completely surrounded by the insulator (3) and the insulator (3) and the inner conductor (2) are accommodated in the outer conductor (4) designed as a sleeve, the electrical feedthrough (1) having an inwardly directed into the housing and an after outwardly directed end area (8), characterized in that the insulator (3) and the outer conductor (4) are covered with a sheet silicate (6) at their end facing the outwardly directed end area (9) of the electrical feedthrough (1). Electrical implementation (1) after claim 1 , characterized in that the layered silicate (6) used is mica. Electrical bushing (1) according to one of the preceding claims, characterized in that the layered silicate (6) is designed as an annular disc with a central opening and the inner conductor (2) protrudes through the central opening. Electrical bushing (1) according to one of the preceding claims, characterized in that the inner conductor (2) forms a circumferential shoulder (5) on which the layered silicate (6) rests. Electrical implementation (1) after claim 4 , characterized in that the outwardly directed end of the insulator (3) and the outer conductor (4) bear against the layered silicate (6) resting on the step (5). Electrical bushing (1) according to one of the preceding claims, characterized in that the layered silicate (6) is fixed in relation to the inner conductor (2) by means of a fixing means (8). Electrical implementation (1) after claim 6 , characterized in that on the outwardly directed end region (9) side of the chic silicate (6) is arranged a bushing (7) which is pierced through a central opening by the inner conductor (2) and by means of the fixing means (8) is fixable. Electrical bushing (1) according to one of the preceding claims, characterized in that the insulator (3), the outer conductor (4) and the shoulder (5) of the inner conductor (2) terminate flush with one another and have a common bearing surface for the layered silicate (6). form. Electrical bushing (1) according to one of the preceding claims, characterized in that the layered silicate (6) has axial flexibility, compression of the layered silicate (6) being produced by an axially acting force component, as a result of which the layered silicate (6) acts as a sealant . Electrical bushing (1) according to one of the preceding claims, wherein the electrical bushing (1) is used in a housing of an exhaust line, characterized in that the sheet silicate (6) is arranged on the end region of the electrical bushing (1) outside the housing .

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