Measuring and testing – Gas analysis – With compensation detail
Patent
1997-12-14
1999-03-09
Williams, Hezron
Measuring and testing
Gas analysis
With compensation detail
73 2331, 73 3105, 422 94, G01N 2758, H01L 700, B60H 132
Patent
active
058803530
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF INFORMATION
The present invention proceeds from a gas sensor, in particular for determining the oxygen content in exhaust gases of combustion engines.
U.S. Pat. No. 4,597,850 discloses a gas sensor having a sensor element, in which the sensor element is surrounded at the exhaust-gas end by a double-walled protective tube having an outer cylindrical part and an inner cylindrical part. Gas openings are arranged respectively in the enveloping surface of the outer cylindrical part and at the upper end of the inner cylindrical part, so that between the walls of the cylindrical parts the exhaust gas experiences a deflection. This ensures that the exhaust gas does not flow in a straight line onto the sensitive section of the sensor element. The reason is that if the exhaust gas flowed directly onto the sensor element, the particles entrained in the exhaust gas, for example contaminants or condensed water, might damage the sensitive section of the sensor element.
SUMMARY OF THE INVENTION
The sensor according to the invention has, in contrast, the advantage that the protective tube is of simple construction in terms of manufacturing and assembly. The result of the present invention is that the particles entrained in the exhaust gas of combustion engines, such as for example contaminants or condensed water, are prevented from penetrating into the cavity between the inner and outer protective sleeves. Because of the end-surface opening in the outer protective sleeve, the exhaust gas is additionally deflected at the gas entrance. Another advantage of the present invention is that while the available inside diameter of the outer protective sleeve is small, the sensor element in the inner protective sleeve has sufficient safety clearance on all sides from the inner wall of the inner protective sleeve. This safety clearance is necessary because in the event of an impact load, the sensor element is elastically displaced in the inner protective sleeve, and upon impact against the inner wall would be damaged or could be broken.
It is particularly advantageous to use the gap between the outer protective sleeve and inner protective sleeve as a gas inlet opening and/or gas outlet opening. As a result, no additional production steps are needed in order to manufacture the gas inlet openings and/or gas outlet openings in the outer protective sleeve. The result of arranging the gas inlet openings on the flange of the inner protective sleeve is that the condensed water entrained in the exhaust gas does not directly strike the sensitive region of the sensor element. The configuration of the gas openings, with shield-like wall sections placed on top, enhances this effect. A particularly advantageous embodiment exists when the aforementioned are used in combination.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a cross section of a first exemplary embodiment of a gas sensor according to the present invention.
FIG. 2 shows a cross section of a second exemplary embodiment of a gas sensor according to the present invention.
FIG. 3 shows a longitudinal side view of the first exemplary embodiment of the gas sensor according to the present invention.
FIG. 4 shows a cross sectional view along the line IV--IV of FIG. 3.
FIG. 5 shows a cross-sectional view along the line V--V of FIG. 4.
FIG. 6 shows a plan view of the first exemplary embodiment of the gas sensor according to the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a first exemplifying embodiment of an exhaust gas-end section 10 of a sensor, for example an electrochemical oxygen sensor, having a planar sensor element 12 immobilized in gas-tight fashion in a metal housing 11. Housing 11 is constituted at the exhaust-gas end by a cylindrical housing section 14.
Sensor element 12 consists of an oxygen ion-conducting solid electrolyte ceramic having electrodes (not depicted). At least one electrode is exposed to the exhaust gas, and constitutes a sensitive region 13 on sensor element 12. The planar sensor element 12 is laminated together fro
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Eisenschmid Heinz
Graser Theodor
Hoetzel Gerhard
Wehrmann Johann
Robert & Bosch GmbH
Wiggins J. David
Williams Hezron
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