Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1995-09-29
1998-01-27
Pyon, Harold Y.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204424, 204427, 204426, 422 94, 422 98, G01N 2746
Patent
active
057118639
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/DE94/00536, filed May 11, 1994, published as WO94/28404 Dec. 8, 1994.
BACKGROUND OF THE INVENTION
The invention takes as its starting point a measuring-probe arrangement for detecting measured gases flowing in a gas conduit. In the known measuring-probe arrangements (U.S. Pat. No. 4,756,885), a protective tube is provided, surrounding which surrounds a clearance that section of a measuring element composed essentially of ceramic material which projects from a tubular housing at the measured-gas end. The bottom of the protective tube at the measured-gas end has a gas opening to allow the measured gas to be fed to the measuring probe. To allow flow through the protective tube, a plurality of outlet openings are provided for the emergence of the measured gas in the side wall of the protective tube near to the measured-gas end of the housing. However, this arrangement of the inlet opening and the outlet openings does not prevent measured gas from entering the protective tube through the outlet openings, some of which face in a direction opposite to the direction of flow of the measured gas, and, as a result, the condensation water which forms particularly in exhaust systems of internal combustion engines reaches the ceramic measuring element. If the condensation water comes into contact with the heated ceramic of the measuring element, the temperature shock can give rise to cracks in the ceramic which can ultimately lead to the failure of the measuring element. The known measuring probes are furthermore screwed into the gas conduit by means of a thread arranged on the housing of the measuring probe. As a result, directional installation is not possible, and the gas openings in the protective tube may face in any direction.
SUMMARY AND ADVANTAGES OF THE INVENTION
The measuring-probe arrangement according to the invention, has a measuring element with a section, known as the measured-gas end, projecting from a housing into an opening in the gas conduit. The measured-gas end is surrounded by a protective tube having at least one gas opening. The gas openings are arranged on the side of the protective tube facing away from the direction of gas flow in the gas conduit. The measuring-probe of the invention also has a marking on the region of the measuring-probe outside the gas conduit which indicates the position of the gas opening the invention has the advantage that the condensation water does not reach the ceramic measuring element.
For the correct orientation of the gas openings in the gas conduit, it is particularly advantageous to insert the measuring probe in an adjustable manner. This is expediently achieved by inserting the measuring probe into a flange arranged on the gas conduit and by fastening it with a union nut. The opening in the gas conduit may also have a sealing surface on which a collar on the housing of the measuring-probe rests, creating an airtight seal.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the invention is illustrated in the drawings and explained in greater detail in the description which follows. FIG. 1 shows a cross section of the measuring-probe arrangement according to the invention and FIG. 2 shows a section of a protective tube with a plurality of gas openings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The measuring probe shown in the drawings is a measuring probe 10 for determining the oxygen content in exhaust gases in, for example, an exhaust conduit 30 of an internal combustion engine. The measuring probe 10 has a measuring element 13 which operates on the known principle of oxygen ion conduction by a solid electrolyte. The solid electrolyte used is preferably stabilized zirconium dioxide. In the example under consideration, the measuring element 13 is a planar sensor of laminar construction. However, it is equally conceivable to use a so-called finger sensor formed by a solid-electrolyte tube as the measuring element 13. The measuring element 13 is not illustrated and described here. Reference is made, for
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Fries Romuald
Henkelmann Konrad
Pyon Harold Y.
Robert & Bosch GmbH
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