Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1999-01-27
2001-05-22
Tung, T. (Department: 1743)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S426000, C205S784500
Reexamination Certificate
active
06235174
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a gas sensor, in particular for determining an oxygen content in exhaust gases of internal combustion engines.
BACKGROUND INFORMATION
A conventional gas sensor includes a sensing element fastened sealedly in a housing. The sensing element is typically configured as a planar sensing element that has a first electrode exposed to a measured gas and a second electrode exposed to a reference gas. In order to deliver a reference gas onto the reference gas electrode, there is provided inside the sensing element a reference gas conduit, running in its longitudinal extension, which can be connected, at an end of the sensing element remote from the measured gas, to a reference gas source, for example the atmosphere. The reference gas conduit terminates at one end surface of the sensing element, and is connected to the reference gas source via a retaining and sealing element of the sensing element that is fastened in a housing of the gas sensor.
For example, German Patent No. 41 26 378 describes a conventional gas sensor. It is disadvantageous in this context that the reference gas conduit terminating at the end face cannot be adequately sealed against possible contaminants. In order to prevent undesired signal falsification, however, the reference gas conduit must be securely sealed against the penetration of substances, for example outside gases, which might falsify the reference gas.
SUMMARY OF THE INVENTION
The gas sensor according to the present invention has an advantage that reliable sealing of the reference gas conduit is possible in a simple fashion. Because the reference gas conduit terminates at a large surface of the sensing element and is sealed with a planar sealing fit, it is easy to achieve hermetic sealing of the reference gas conduit using a planar pressure that is preferably provided. Especially because the reference gas conduit terminates at a large side of the sensing element, a sufficiently large surface surrounding the outlet of the reference gas conduit is available for constituting the planar sealing fit.
In a preferred embodiment of the present invention, provision is made for the reference gas conduit to be sealedly joined to a reference gas guidance element that runs parallel to the sensing element and ends at a side of the gas sensor facing away from the measured gas. The reference gas guidance element very advantageously makes possible a prolongation of the reference gas conduit using a carrier which sealingly retains the sensing element. It is further preferred if a sealing element, preferably of planar configuration, is arranged between the reference gas guidance element and the outlet of the reference gas conduit. A good sealing effect is attained in particular if the sealing element is plastically deformable during assembly of the gas sensor.
In a further preferred embodiment of the present invention, provision is made for the reference gas guidance element simultaneously to provide contacting of at least one of the electrodes of the sensing element. This results in sealed guidance of the reference gas and simultaneously in a sealed passthrough contact to at least one of the electrodes through the retaining element.
In a further preferred embodiment of the present invention, provision is made for the reference gas guidance element to be formed by the retaining element, the retaining element preferably comprising a ceramic shaped element which has the integrated reference gas guidance element. It is thereby possible, with few parts, to combine sealed connection of the reference gas conduit of the sensing element with sealed immobilization of the sensing element in the housing of the gas sensor.
REFERENCES:
patent: 4096050 (1978-06-01), Kobayashi et al.
patent: 4362609 (1982-12-01), Sano et al.
patent: 4526672 (1985-07-01), Reed
patent: 4588494 (1986-05-01), Kato et al.
patent: 5246562 (1993-09-01), Weyl et al.
patent: 5830339 (1998-11-01), Watanabe et al.
patent: 41 26 378 (1992-04-01), None
Kenyon & Kenyon
Robert & Bosch GmbH
Tung T.
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