Electro-chemical measuring sensor

Details Electro-chemical measuring sensor Electro-chemical measuring sensor

1996-02-06

1997-12-16

Tung, T.

Chemistry: electrical and wave energy

Apparatus

Electrolytic

204427, 204428, G01N 27407

Patent

active

056980841

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention is based on an electro-chemical measuring sensor for determining the oxygen content of gases, in particular for determining the oxygen content of exhaust gases of internal combustion engines, with a sensor element inserted into a housing with a seal ring, which has an oxygen ion-conducting solid electrolyte body in the form of a tube closed on one side. Electro-chemical measuring sensors are designed, for example, with a sensor element of a so-called finger shape, wherein a solid electrolyte body in the shape of a closed tube is sealingly fixed in place in a metallic housing. Differentiations are made in connection with finger sensors between potential-free and potential-dependent measuring sensors. With potential-dependent measuring sensors, the strip conductors of the outer electrodes are brought into contact with the housing by means of an electrically conductive sealing ring. With potential-free measuring sensors, each electrode connection is directly supplied to a control instrument, so that electrical contact with the housing is not permitted. Sealing between the solid electrolyte body and the housing must be provided in either case.
2. Description of the Related Art
Potential-free measuring sensors in particular, wherein a contact for each electrode connection is disposed on the annular surface of the solid electrolyte body, require a positionally correct seating of the contact elements. There is the danger that during the installation of the measuring sensor the solid electrolyte body is twisted after having been inserted and that therefore the contacts of the electrodes take up a different position, because of which assured contact is impossible.
A metallic sealing ring, for example, is used for sealing the solid electrolyte body in the housing, wherein with a potential-free measuring sensor the strip conductor to the outer electrode in the area of the metallic sealing ring must be covered with electrical insulation.


SUMMARY OF THE INVENTION

The measuring sensor in accordance with the invention and having the characterizing features that means are provided which maintain the sensor element in the housing under mechanical prestress, which has the advantage that the sensor element is fixed in place in the housing secure against relative rotation. By means of this a secure contact of the electrode connections is possible, particularly in connection with the mounting of potential-free measuring sensors.
Advantageous further embodiments of the measuring sensor in accordance with the invention are possible by the measures recited in the dependent claims. In particular, the means are constituted by at least one resilient element formed on the seal ring. The seal ring may have a ring element on which the resilient elements are formed evenly radially distributed. The resilient elements may be embodied with respectively one lower part and an outwardly angled off upper part and have a clear width (W) in such a way that the lower parts rest against the sensor element under mechanical prestress and the upper parts are supported under mechanical prestress on the housing. The seal ring may consist of Cr--Ni steel with an applied ductile layer of Ni or Cu. A simple fixing in place of the sensor element in the housing, which is secure against relative rotation, can be realized by means of a specially designed seal ring which maintains the sensor element in the housing under mechanical prestress. Equipping the seal ring with resilient elements has been shown to be particularly practical.


BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is represented in the drawings and explained in more detail in the following description. Shown are, in FIG. 1, a longitudinal section through the portion of the measuring sensor on the exhaust gas side; in FIG. 2, an enlarged section of the sealing zone X in FIG. 1; in FIG. 3, a top view of a seal ring and, in FIG. 4, a sectional representation along the line IV--IV in FIG. 3.


DESC

REFERENCES:
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patent: 5246562 (1993-09-01), Weyl et al.
patent: 5573650 (1996-11-01), Fukaya et al.

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