Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Patent
1997-07-15
1999-09-07
Kincaid, Kristine
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
174 85, 174 65G, H01R 422
Patent
active
059490233
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a temperature-resistant, tightly sealed cable bushing in a housing, in particular in a gas sensor housing, with a molded body arranged inside the housing, through which at least one connecting cable with an electrical conductor and a cable insulation are fed, as well as a method for the manufacture of said cable bushing.
2. Description of the Related Art
Tightly sealed and high-temperature resistant cable bushings are required, for example, for gas sensors, in particular for Lambda probes. These gas sensors have a housing with a sensor element arranged on the inside. The sensor element is contacted inside the housing with connecting cables. The connecting cables exit the housing through a cable bushing. The gas sensors for determining the exhaust-gas composition in motor vehicles are inserted into the exhaust pipe and are thus subjected to the environmental influences prevalent there. The sensor element arranged inside the housing operates as a rule with reference air, which is fed into the housing, for example, via the cable insulation. However, it is critical on the other hand that the sensor element inside the housing does not come in contact with negative environmental influences such as dirt, oil and/or water. This necessitates that the cable bushing is designed such that it forms a tight seal against the housing as well as against the cable insulation.
From the Federal Republic of Germany Application No. 41 26 378 A1, a cable bushing is known for which the connecting cables are fed through an elastic, plug-like molded body. The molded body is composed of a temperature-resistant material, e.g. PTFE (TEFLON), and is enclosed and pressed together by a housing sleeve that forms the housing. An O-ring is additionally inserted as a seal between housing sleeve and molded body. The O-ring is composed of an elastomer, for example Viton, and has only a limited temperature stress tolerance. The use of this cable bushing at higher temperatures, such as are present if the gas sensor is arranged close to the motor exhaust, is therefore limited with respect to the temperature resistance of the seal.
SUMMARY OF THE INVENTION
In contrast, the invention provides a molded body designed with a ring groove, which starts on one frontal side and extends axially inside the molded body and forms a cylinder wall toward the housing, and a support ring is arranged inside the ring groove, and has the advantage that the cable bushing ensures a temperature-resistant, lasting and reliable seal. The design of the cylinder wall achieves that the material for the molded body does not flow too strongly when heated up, but retains its position between the supporting ring and the housing.
Owing to the measures listed in the dependent claims, advantageous embodiments and modifications of the invention are possible. In order to limit the flowability of the material for the molded body at higher temperatures, it is advantageous to keep the wall thickness for the molded body to a minimum between ring groove and housing sleeve. An especially suitable, tight connection between molded body and cable insulation can be achieved if both parts are composed at least partially of the same material. Particularly suitable as a material is PTFE (TEFLON), which has the advantage of having a high temperature resistance with simultaneously high sealing capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
One exemplary embodiment of the invention is shown in the drawing and is explained in more detail in the description below.
FIG. 1 shows a sectional view of a gas sensor,
FIG. 2 shows a sectional view of a molded body for an inventive cable bushing, and
FIG. 3 shows a sectional view through the cable bushing for the gas sensor, along the lines III--III in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a gas sensor 10, for example an electrochemical oxygen sensor with a metal housing 12, having a thread 13 as fastening means for installation into a non-depicted meas
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patent: 5540450 (1996-07-01), Hayashi et al.
patent: 5625167 (1997-04-01), Von Noten et al.
Kincaid Kristine
Kunitz Norman N.
Nguyen Chau N.
Robert & Bosch GmbH
Wells Ashley J.
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