DE2350253C3 - Electrochemical probe - Google Patents

Description

consists.

6. Electrochemical sensor according to one of claims 2 to 4, characterized in that the Sealing ring (39) made of a heat-resistant, plastically deformable material (41), such as. B. asbestos.

rer metal ring (40), which is preferably made of nickel 40 zirconium dioxide; on the outer surface of this

Solid electrolyte tube 10 is a catalyst layer 12 (platinum) from the bottom 13 to Solid electrolyte tube collar 11 is sufficient. On the inside of the solid electrolyte tube 10 is an electrode in the form a conductor track 14 attached; This conductor track 14 can also consist of platinum, for example. The from Solid electrolyte tube 10 formed cavity 15 is at its connection-side end portion to a bore 16 expanded, up to which the conductor track 14 also extends; the transition from cavity 15 to The bore 16 in the solid electrolyte tube 10 forms a shoulder 17.

The solid electrolyte tube 10 is inserted in the longitudinal bore 18 of a metallic, heat-resistant housing 19 and lies

while with his paragraph 20 located on the federal government 11 a seal 21, which in turn rests indirectly on a shoulder 22, soft between the housing longitudinal bore 18 and a connection-side housing extension 23 is formed; between the seal 21

and the housing shoulder 22 still holds a flange 24 of a protective sleeve 26 provided with air flaps 25, which surrounds the end section of the solid electrolyte tube 10 on the exhaust gas side. For mounting the sensor in one The exhaust pipe carries a screw-in thread 19 'and a hexagon socket on the outside of the housing 19 19 ".

In order to make contact with the conductor track 14 reaching into the cavity bore 16, connecting-

The invention relates to an electrochemical sensor for determining the oxygen content in exhaust gases, in particular in exhaust gases from internal combustion engines, with an ion-conducting, one-sided with a bottomed solid electrolyte tube, the outside of which has an electron-conducting catalyst layer and at the connection-side end section has a collar, wherein the catalyst layer has a Sensor housing is electrically connected to ground and facing the exhaust gases, and its The inside is exposed to the ambient air and one that conducts electrons that extends into the area of its bottom Has track that is connected to a connector.

A number of electrochemical sensors have been proposed in which the incorporation of the Solid electrolyte tube in the sensor housing and also the connection of a connector with de: Conductor on the inside of the solid electrolyte tube

on the other hand, a connector 27 in the solid electrolyte tube cavity IS inside, which is tubular, Has air flaps 28 and a plug contact 29 at its connection-side end portion and with a Pressure sleeve 30 is provided, which is mounted on the connector 27 is pushed on, is fastened with weld points 31 on the connection part 27, one from the solid electrolyte tube bore 16 has protruding flange 32 and with its tubular part in the solid electrolyte tube bore 16 immersed The pressure sleeve 30 rests on a seal 33, the ring-shaped the connecting part 27 and rests on the shoulder 17 in the solid electrolyte tube cavity 15 on the pressure sleeve flange 32 is a ceramic insulating ring 34, which separates the pressure sleeve 30 from the housing 19 electrically A metal ring 35 is arranged on this insulating ring 34 and a compensating element 36 in the form of two Disc springs follows; this compensating element 36 is by the from the connection-side end portion of the Housing 19 formed bead '7 biased. Instead of disc springs as a compensating element 36, spring washers, coil springs, metal sleeves can also be used with a corresponding thermal expansion behavior are used. The from the compensation element 36 The outgoing force is transmitted to the metal ring 35, the insulating ring 34, the pressure sleeve 30, the seal 33 and on the shoulder 17 in the solid electrolyte tube cavity 15; over this shoulder 17 of the solid electrolyte tube cavity 15, the pressure continues to act on the shoulder 20 on the outside of the solid electrolyte tube 10 Seal 21, over protective sleeve flange 24 and then onto housing shoulder 22.

The seal 21 between the housing 19 and the solid electrolyte tube 10 is in three parts, the middle area is formed by an electrically conductive, resilient mass 38 (e.g. graphite powder or copper powder), which is limited at the top and bottom by a sealing ring 39; a thin-walled, easily deformable metal ring 40, which has, for example, a U-shaped profile and preferably made of nickel consists. The electrically conductive mass 38 connects that located on the solid electrolyte tube 10 Catalyst layer 12 with the sensor housing 19 connected to ground.

The seal 33 between the connection part 27 and that located in the interior of the solid electrolyte tube 10 Conductor 14 takes place through a seal which is similar to seal 21: this seal 33, too is in three parts and has in its middle area an electrically conductive, resilient mass 38, the top and

ίο is limited below by a sealing ring 39; in In this case, the sealing ring 39 is a heat-resistant, plastically deformable material 41, such as. B.Asbest

However, the seal 33 can be made of heat-resistant, plastically deformable material 41 instead of the sealing rings 39 also be provided with metal rings 40 as sealing ring 39; likewise, the metal rings 40 in the seal 21 can be replaced by sealing rings 39 made of heat-resistant, plastically deformable material 41.

Electrochemical sensors according to the invention

have only a single compensating element 36, which interacts with the two seals 21 and 33 achieved the required sealing and electrical contacting; the assembly of such sensors does not require the solid electrolyte tube 10 to be heated

and the housing 19, thereby saving substantial costs and reducing the number of faulty sensors during installation.

On the connection-side end section of the housing 19 is a protective tube 42 through weld spots 43

attached; this protective tube 42 contains air inlet openings 44 and an insulating washer 45 on the end face, which is held by a bead 46 and a bead 47 in the protective tube 42 and the plug contact 29 in their slot 48 includes.

In this electrochemical sensor, which is based on the principle of the oxygen concentration chain with Based on ion-conducting solid electrolyte, the ambient air enters through air inlet openings 44 and air flaps 28 and then through the connection tcii interior 49 into the solid electrolyte tube cavity 15.

1 sheet of drawings

Claims (5)

Patent claims: 1. Electrochemical sensor for the determination of the oxygen content in exhaust gases, in particular in exhaust gases from internal combustion engines, with an ion-conducting, one-sided with a Beden provided solid electrolyte tube, the outside of which has an electron-conducting catalyst layer and am connection-side end section has a collar, the catalyst layer over a sensor housing is electrically connected to ground and facing the exhaust gases, and its Inside is exposed to the ambient air and one that extends into the area of its bottom has an electron-conducting path which is connected to a connector, characterized in that that between the longitudinal bore shoulder (22) of the housing (19) and the shoulder (20) on the solid electrolyte tube collar (11) and / or between is quite complicated and expensive; in addition, pointed these constructions have weaknesses in terms of their seals between the solid electrolyte tube and the housing or the connector. In contrast, the invention is based on the object of providing an electrochemical measuring sensor create, which has a simplified structure and a reliable seal between the solid electrolyte tube and housing or connector This object was achieved according to the invention in that between the longitudinal bore shoulder of the Housing and the shoulder on the solid electrolyte tube collar and / or between the drilling shoulder of the solid electrolyte tube and the connection part-pressure sleeve resilient electrically conductive seals are arranged, and that with the solid electrolyte tube or the connecting part pressure sleeve at least one compensating element is in operative connection; this works with this solution Solid electrolyte tube or the connector pressure sleeve Drilled shoulder (17) of the solid electrolyte tube 20 at the same time as a pressure element for the seal (10) and the connecting part pressure sleeve (30) flexible, electrically conductive seals (21,33) are arranged are, and that with the solid electrolyte tube (10) or the connecting part pressure sleeve (30) at least a compensating element (36) is in operative connection. 2. Electrochemical sensor according to claim 1, characterized in that the electrically conductive Seal (21, 33) is a resilient, electrically conductive mass (38), the top and bottom through each a sealing ring (39) is limited. 3. Electrochemical sensor according to claim 2, characterized in that the mass (38) Graphite powder is. 4. Electrochemical sensor according to claim 2, characterized in that the mass (38) Copper powder is. 5. Electrochemical sensor according to one of claims 2 to 4, characterized in that the Sealing ring (39) consists of a thin-walled, easily deformable seal such as this according to a development of an electrically conductive mass, the top and bottom by one Sealing ring is limited; the mass preferably consists of graphite powder or copper powder. The sealing rings are made of heat-resistant, plastically deformable material, such as. B. Asbestos, but it can also be thin-walled, easily deformable metal rings, which are preferably made of nickel. An embodiment of the invention is shown in the drawing and is described below and explained in more detail; the figure shows a longitudinal section through a shown enlarged electrochemical sensor according to the invention. The sensor according to the invention shown in the figure contains a solid electrolyte tube closed on one side 10, which has a collar 11 on the outside at its open end section and is made of stabilized cubic