Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1995-12-04
1998-08-18
Tung, T.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204426, 204427, 204428, 277316, 277650, 277936, 277938, 277939, 277941, 277943, G01N 27407, F16J 1514
Patent
active
057954542
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is based on a seal for a sensor element of a gas sensor particularly for determining the oxygen content in exhaust gases of internal combustion engines, which seal seals the sensor element in a longitudinal bore of a housing. The sensor elements used to determine the oxygen content in exhaust gases of internal combustion engines include, on the one hand, a so-called finger construction, in which an electrochemical solid electrolyte is configured as a tube that is closed on one side and is fixed in the housing in a sealed manner. In the other known, so-called wafer sensors, a planar, oxygen-conductive solid electrolyte is likewise sealingly fixed in the housing.
2. Description of the Related Art.
In DE-OS 41 26 378, a seal for a wafer sensor is described which is located between two ceramic formed parts disposed in the housing, with the ceramic formed parts securing the sensor element in the housing. The seal in this instance is made of soapstone.
Finger sensors are divided into potential-free and potential-bound gas sensors. In potential-bound finger sensors, the conductor path of the outer electrode is contacted with the housing by means of an electrically-conductive sealing ring. In potential-free finger sensors, each electrode connector is guided directly to a control device, so that no electrical contact with the housing is permitted. For potential-free finger sensors, it has already been proposed to use a deformable, electrically-insulating, ceramic sealing ring.
Both the deformable ceramic sealing ring in the finger sensor and the seal material used in the wafer sensor are pre-sintered at low sintering temperatures, by means of which a residual porosity is retained, even under high pressing forces, which has the disadvantage that water and fuel diffuse through the seal due to capillary forces.
SUMMARY OF THE INVENTION
In contrast, the seal of the invention has a deformable additional seal which has a lesser porosity than two sealing bodies, is disposed between the two sealing bodies, and has the advantage that it is impermeable to liquids, particularly fuel. A seal with respect to liquid fuel is required particularly if fuel enters the exhaust pipe when the internal combustion engine experiences difficulty starting.
Advantageous modifications and improvements of the seal disclosed in the main claim are possible with the measures outlined in the dependent claims. Thus, the sealing bodies may be pre-sintered and may be pressed, with the additional seal, into the longitudinal bore, wherein the additional seal becomes deformed during pressing such that the sensor element is disposed gap-free in the longitudinal bore. The additional seal may be a pre-formed sealing disk or a pre-formed sealing ring. The additional seal may be made of a ductile metal, preferably nickel or copper. The ductile metal can be used in the form of a pre-pressed powder or in solid form. The additional seal may be made of graphite and the graphite may be fiber-reinforced. A particularly good seal is achieved when the sealing body and the additional seal are pressed together in the housing. This causes the additional seal to lie gap-free between the sensor element and the housing. Graphite has proven to be especially well-suited as a material for the additional seal: because of its lamellar structure, it is impermeable to water and fuel under correspondingly high compression.
BRIEF DESCRIPTION OF THE DRAWINGS
Two embodiments of the invention are illustrated in the drawing and described in detail in the following description. gas sensor having a finger sensor, FIG. 2 shows an enlarged section of the seal according to FIG. 1, and
FIG. 3 shows a longitudinal section through the exhaust-gas-side part of a gas sensor having a wafer sensor.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows an electrochemical oxygen gas sensor 10 having a metallic housing 11 which has a hexagonal nut 12 and a thread 13 as fastening means for installation into a measuring gas
REFERENCES:
patent: 3891529 (1975-06-01), Beesch
patent: 3960692 (1976-06-01), Weyl et al.
patent: 4088555 (1978-05-01), Kita
patent: 4141813 (1979-02-01), Kita et al.
patent: 4732663 (1988-03-01), Kato et al.
patent: 4818363 (1989-04-01), Bayha et al.
patent: 4986892 (1991-01-01), Kato et al.
patent: 5246562 (1993-09-01), Weyl et al.
Fries Romuald
Friese Karl-Hermann
Hans Anton
Weyl Helmut
Wiedenmann Hans-Martin
Robert & Bosch GmbH
Tung T.
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