Measuring and testing – Gas analysis – With compensation detail
Patent
1998-05-26
2000-02-01
Williams, Hezron
Measuring and testing
Gas analysis
With compensation detail
73 2332, 73 3105, 204424, 204410, 422 83, G01N 27407, G01N 2726
Patent
active
060189827
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND INFORMATION
The present invention is directed to a sensor, for determining the oxygen content of exhaust gases produced by internal combustion engines to. The German Published Unexamined Application No. DE-OS 27 02 432 discloses a Lambda probe type gas sensor of this type, for example, where the reference air is introduced via a connecting cable into the housing, and the cavities disposed in the connecting cable insulation are not always sufficient to conduct enough reference air into the interior of the sensor's housing. One has to consider here that this reference air must be renewed at regular intervals, i.e., it must be coupled to the ambient air. On the other hand, to achieve unbiased measuring results, it is absolutely necessary that the reference air not come in contact with the exhaust gas to be measured, or e.g., with dirt, water, oil or gasoline from the ambient air. According to today's state of technological development, reference air is coupled to ambient air by way of a cable core, i.e., by way of the inner stranded conductor of the measuring cable, e.g., from the control unit. When the cable is lead through the measuring probe, the insulation sheath of the measuring cable must be sealed off absolutely imperviously. This process of leading the cable through is quite complex, since it requires manufacturing and assembling various components. This complexity is reflected accordingly in the manufacturing costs.
SUMMARY OF THE INVENTION
The connecting line according to the present invention has the advantage of enabling an improved supplying of reference atmosphere into the housing. The orifices placed in the sheath surface of the cable covering made of PTFE are sized to permit a sufficient quantity of reference air to penetrate through these gas-permeable sections to the inside of the cable covering and, from there, into the housing on the other hand, these gas permeable sections prevent the ingress of liquids, such as fuel, water, etc. It is particularly beneficial from a standpoint of production engineering, for the cable insulation to have orifices which are sheathed by an additional PTFE film, the PTFE film being pretreated to have a porosity which will, in fact, allow gas to arrive inside the housing, but not liquids or moisture or impurities. Since the additional PTFE film can be modified in different ways, one can advantageously adjust its specific permeability, through proper treatment, to hinder or prevent the otherwise critical diffusion of liquid hydrocarbon compounds. The additional PTFE film is advantageously shrink-fit onto the gas-permeable section of the PTFE line.
BRIEF DESCRIPTION OF THE DRAWING
An exemplary embodiment of the invention is shown in the drawing and elucidated in the following description. The only Figure shows a section through a cable sleeve, with the connecting cable of the present invention built into a lambda probe.
DETAILED
The figure shows a cross-section through the terminal side of a sensor 1, for example a lambda probe. This terminal side includes a housing 2 (partially shown), in which a sensor element 20 (not shown) is fixed in a gas-tight manner. Sleeve body 3 is disposed within housing 2. Two connecting cables 4, 5 extend right through sleeve body 3 and are provided at their lower end with crimp contacts 6, 7. Insulation sheaths 12, 13 are joined with form locking along their entire periphery to sleeve body 3. Placed at a distance L of, for example, 2 cm from housing 2 on the insulation sheaths 12, 13 are orifices 17, which are covered by an additional porous PTFE film 18, forming a traversing air-exchange channel between the sensor (not shown) and the outside air. Because insulation sheaths 12, 13 are permanently joined to sleeve body 3, all deformations in response to heating or cooling of sleeve body 3 are coupled to insulation sheaths 12, 13. Sleeve body 3 is secured by caulking in housing 2, which is why housing 2 has a toroidally-shaped protrusion 8, and sleeve body 3 has a torus 9 which fits into protrusion 8 and includes
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Friese Karl-Hermann
Hans Anton
Weyl Helmut
Robert & Bosch GmbH
Wiggins J. David
Williams Hezron
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