Electricity: conductors and insulators – Conduits – cables or conductors – Conductive armor or sheath
Reexamination Certificate
1997-11-18
2001-02-13
Kincaid, Kristine (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Conductive armor or sheath
C174S1020SP
Reexamination Certificate
active
06188025
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat-resisting metal-sheathed cable for a sensor such as an oxygen sensor or thermistor which is disposed in a high temperature place in an automobile or the like.
2. Description of the Related Art
An oxygen concentration cell type oxygen sensor is heretofore known as a sensor for detecting an air-fuel ratio of an internal combustion engine such as an automotive engine. The oxygen sensor includes a pair of porous electrodes disposed on the opposite sides of a partition wall member made of an oxygen ion conductive solid electrolyte and is constructed so as to put one of the porous electrodes into contact with the reference gas and the other into contact with the measured gas (i.e., gas to be measured) such that the oxygen concentration is measured based on the electromotive force cell across the electrodes.
Accordingly, it is important that the reference gas is accurate. For example, if gasoline, water or the like into a chamber containing the reference gas, the reference gas is contaminated resulting in inaccurate detection. For this reason, it has heretofore been practiced to provide the chamber with an air-tight wall surrounding the reference gas thereby preventing ingress of contaminants into the chamber.
However, the above described technology still has a difficulty in preventing the ingress of contaminants completely, so it has been proposed to provide the chamber with an atmospheric air introducing hole which is devised to make it difficult for the contaminants to intrude therethrough into the chamber such that the chamber can be ventilated so as to contain the normal atmospheric air even if the contaminants intrude into the chamber a little.
For example, it is disclosed in Japanese utility model provisional publication No. 56-4852 such a technology of using a covered harness having an insulation covering made of a resinous material for fetching or output of signal, providing the harness with a hollow portion at the axial center thereof and using the hollow portion as a ventilation hole for passage or conduction of the atmospheric air.
However, since the recent oxygen sensors are generally used at a high temperature, such a harness having a resinous covering encounters a problem that it cannot withstand the heat at a high temperature.
Another technology describes a sensor provided with a filter for thereby attaining the permeability. However, this technology utilizes a filter made of a resinous material and thus encounters a problem that the sensor cannot be used at high temperatures.
As a countermeasure to such a problem, it is considered to use a stainless steel (SUS)-sheathed wire having a good resistance, for the above described harness. However, since a mass of magnesia power is used in the conventional SUS-sheathed wire as an insulator, it is difficult to form such a hollow portion as in the resinous harness, in the mass of magnesia powder. For this reason, the above described countermeasure encounters a problem that a desired ventilation hole cannot be formed in such a SUS-sheathed wire.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a novel and improved heat-resisting metal-sheathed cable for a sensor, which comprises a sheathing tube made of heat-resisting metal, at least one conductor and at least one ventilation tube disposed at a predetermined interval within the sheathing tube, the ventilation tube being made of heat-resisting metal, and a mass of insulating powder filled in the sheathing tube in a way as to surround the conductor and the ventilation tube. Thus, the filling of the insulation powder within the sheathing tube makes it possible to attain a sufficient heat-resisting ability and a sufficient insulating ability, while making it possible to attain the ventilating ability by means of the ventilation tubes made of heat-resisting metal and disposed within the mass of insulating powder for the purpose maintaining the quality of the reference gas of the oxygen sensor.
According to a second aspect of the present invention, there is provided a heat-resisting metal-sheathed cable for a sensor, which comprises a sheathing tube made of heat-resisting metal, a pair of conductors and a pair of ventilation tubes disposed at predetermined intervals within the sheathing tube, the ventilation tube being made of heat-resisting metal, and a mass of insulating powder filled in the sheathing tube in a way as to surround the conductors and the ventilation tubes, wherein the conductors are respectively positioned at two of four corners of a square and the ventilation tubes are respectively positioned at remaining two of said four corners when observed in a cross sectional view of the sheathing tube. Though the inner diameter of the sheathing tube made of heat-resisting metal is generally so small, a short circuit between the conductors or the like fault never occurs since the pair of conductors and the pair of ventilation tubes are disposed so as to be positioned at four corners of a square, i.e., disposed so as to be distant from each other as much as possible according to the present invention.
According to a third aspect of the present invention, there is provided a cable as set forth in the second aspect, wherein the conductors and the ventilation tubes are disposed diagonally, respectively. By this, the conductors are disposed at diagonal positions, i.e., at positions most distant from each other, so a short circuit, or the like fault never occurs between the conductors. This is because the conductors are disposed so as to oppose diametrically each other, particularly when the ventilation tubes have a large diameter.
According to a fourth aspect of the present invention, there is provided a heat-resisting metal-sheathed cable for a sensor, which comprises a sheathing tube made for heat-resisting metal, a ventilation tube made of heat-resisting metal disposed concentrically within the sheathing tube, a plurality of conductors disposed at predetermined intervals within the sheathing tube and around the ventilation tube, and a mass of insulating powder filled in the sheathing tube in a way as to surround the conductors and the ventilation tube. The arrangement of disposing the ventilation tube concentrically within the sheathing tube enables the diameter of the ventilation tube to be set larger. Accordingly, sufficient ventilation can be attained even when a number of conductors are used in the cable.
According to a fifth aspect of the present invention, there is provided a cable according to the fourth aspect, wherein the conductors are respectively positioned at four corners of a square when observed in a cross sectional view of the sheathing tube. Though a short circuit is liable to be caused in case four conductors are used, this arrangement of disposing the conductors at positions distant from each other makes it possible to prevent a short circuit.
According to a sixth aspect of the present invention, there is provided a heat-resisting metal-sheathed cable for a sensor, which comprises an outer sheathing tube made of heat-resisting metal, an inner sheathing tube made of heat-resisting metal and disposed within the outer sheathing tube in a way as to provide between the two tubes a predetermined gap constituting a ventilation passage, at least one conductor disposed within the inner sheathing tube, and a mass of insulating powder filled in the inner sheathing tube in a way as to surround the conductor. By this, the space or passage for ventilation is shaped annular in cross section, so there is the advantage that the space can be made larger.
According to the seventh aspect of the present invention, there is provided a cable according to the sixth aspect, wherein the outer and inner sheathing tubes are secured to each other with welding. By this, the outer and inner sheathing tubes are assuredly held fixed or stationary to each other, thus making it possible to prevent the outer and inner sheathing tubes from striking against
Hanai Shuichi
Nakao Takashi
Nishio Hisaharu
Yabuta Katsuhisa
Foley & Lardner
Kincaid Kristine
Mayo, III William H
NGK Spark Plug Co. Ltd.
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