Abstract:
An insulating cover for at least two electrical conductors includes two adjacent parallel tunnels, each arranged to receive one electrical conductor for the purpose of economical fabrication and the avoidance of insulation damage even over the long term, made by shaping at least one long, thin, flexible strip of electrically insulating material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    The present application claims priority to Application No. 101 38 124.7, filed in the Federal Republic of Germany on Aug. 3, 2001, which is expressly incorporated herein in its entirety by reference thereto.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates to an insulating cover for at least two parallel-extending electrical conductors.  
         BACKGROUND INFORMATION  
         [0003]    In a hookup connection for a detector, in particular for determining the oxygen content in exhaust gases of internal combustion engines, as described in German Published Patent Application No. 195 23 911, at least two electrical connecting leads for the sensor element of the detector are guided inside a metal tube the end of which is affixed to a detector housing. For the purpose of electrically insulating the connecting leads from each other and from the metal tube, each connecting lead is surrounded by braided glass silk resistant to a temperature of about 700° C. Alternatively, a braiding of ceramic fibers enclosing the connecting lead is used, which reaches a temperature resistance of about 1200° C. At the sensor end and at the connector end of the connecting lead, the insulation is stripped from the electrical conductors, in order to produce a crimp connection to the sensor element and to the connecting plug.  
         SUMMARY  
         [0004]    The insulating cover according to the present invention provides a construction of the insulating cover out of one, two or more flat, flexible insulating strips forming a tunnel as the conductors pass through. This arrangement may allow the possibility of using a great number of different, economical electrically insulating materials which—in contrast to glass silk—are not suitable for braiding around conductors, to insulate parallel-extending conductors. The insulating cover may ensure a fixed arrangement of the parallel-extending conductors, so that the conductors are resistant to vibratory excitation and, even in long-term operation, damage to the insulation may not occur, such as is caused in the case of freely adjacent conductors sheathed in insulation by the jackets chafing against each other. Fabrication of the insulating covers is simple and economical, and the fabrication costs may be lowered further by selecting an inexpensive material. Depending on the number of conductors to be contained in the insulating cover, by using only one insulating strip with turned up longitudinal edges or two or more flat insulating strips, two or more tunnels may be formed with one conductor passing through each. The simple separation of insulating cover and conductor may make the insulating cover readily recyclable.  
           [0005]    According to an exemplary embodiment of the present invention, each insulating strip is formed from one layer of a textile fabric. The textile fabric is shaped by sewing so that the tunnels are formed between the longitudinal seams.  
           [0006]    In order to obtain tunnels with particularly large cross-sectional clearance, according to an exemplary embodiment of the present invention, the seams that extend in the longitudinal direction of the layers of textile fabric may be arranged, in at least one layer of textile fabric, at a lateral distance from each other that is smaller than the width dimension of the remaining sections between the seams, so that these sections bulge or arch up and allow greater cross-sectional clearance between them.  
           [0007]    The insulating cover according to the present invention may be used in a hookup connection for a sensor such as is used to determine the oxygen content or the temperature in the exhaust gas of an internal combustion engine. A hookup connection of this type is distinguished by the fact that the conductors which are used to connect a sensor of a detector located in a detector housing with a plug extend inside of a metal tube, one end of which is affixed to the metal detector housing and the other end to a plug housing. In the plug housing, electrical connections are made to sheathed connecting cables, which have their ends secured in a connecting plug, so that an interface between the electrical conductors and the connecting cables is formed in the plug housing. The insulating cover according to the present invention is drawn into the metal tube, and receives the desired number of electrical conductors in its tunnels described above, so that the electrical conductors are electrically insulated both from each other and from the metal tube. Through the use of the insulating cover according to the present invention, it is possible to use bare solid wires or stranded wires as conductors, eliminating the stripping of insulation from the formerly used sheathed conductors to produce the crimped contacts at the sensor element and plug. Because of the flat insulating cover, it is also possible to flatten the metal tube, thus allowing extremely small bending or folding of the metal tube, making it possible to reduce the installation space which may be reserved for installation of the detector in the exhaust system of the internal combustion engine.  
           [0008]    When solid wires are used as electrical conductors, in combination with the insulating cover according to the present invention, undulations may be formed in the composite of solid wires and insulating cover extending in the longitudinal direction of the metal tube, which may be used to equalize the length of the composite with the metal tube or to brace the composite against the interior wall of the tube.  
           [0009]    If the hookup connection uses sheathed stranded hookup wires as electrical conductors to connect the sensor element directly to the plug contacts of the connecting plug, eliminating the interface between conductor and connecting cable described earlier, the insulating cover according to the present invention may be used here as well. The insulation may be stripped from the sections of the stranded wire extending in the area of the metal tube, since the PTFE sheathing of the stranded wires is not sufficiently heat-resistant. The stripped sections of the stranded wires are carried in the tunnels of the insulating cover being utilized, and are thus insulated from each other and from the metal tube. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a cross-sectional view of a longitudinal section of a detector having a hookup connection to a connecting plug.  
         [0011]    [0011]FIG. 2 is a perspective view of a detector end of the hookup connection.  
         [0012]    [0012]FIG. 3 is a cross-sectional view (top) and part of a top view (bottom) of an example embodiment of an insulating cover in the hookup connection illustrated in FIGS. 1 and 2.  
         [0013]    [0013]FIG. 4 is a cross-sectional view (top) and part of a top view (bottom) of another example embodiment of an insulating cover in the hookup connection illustrated in FIGS. 1 and 2.  
         [0014]    [0014]FIG. 5 is a cross-sectional view (top) and part of a top view (bottom) of another example embodiment of an insulating cover in the hookup connection illustrated in FIGS. 1 and 2.  
         [0015]    [0015]FIG. 6 is a cross-sectional view (top) and part of a top view (bottom) of another example embodiment of an insulating cover in the hookup connection illustrated in FIGS. 1 and 2. 
     
    
     DETAILED DESCRIPTION  
       [0016]    A detector  10  illustrated in FIG. 1 in a partial longitudinal section may be used, depending on the arrangement, as an exhaust gas temperature sensor for determining the exhaust gas temperature of an internal combustion engine or as a compact lambda probe for determining the oxygen content in the exhaust gas of the internal combustion engine.  
         [0017]    The detector  10  has a sensor element  12  positioned in a detector housing  11 . In FIG. 1 only the end of the sensor element inserted into an electric coupler  13  and in contact with a hookup connection  14  is illustrated. Hook-up connection  14  produces an electrical connection of detector  10  with a connecting plug. In the exemplary embodiment illustrated in FIGS. 1 and 2 for a detector  10  in the form of an exhaust gas temperature sensor, hookup connection  14  has two stranded wires  15  producing an electrical connection between electric coupler  13  in detector housing  11  and a connecting plug, and a metal tube  16  which is fixed at one end in detector housing  11  and receives the section of stranded wires  15  close to the detector. Each flexible stranded wire  15  includes a conductor  151  having a plurality of thin individual wires of a temperature-resistant material of low specific resistance little dependent on temperature, and of an insulating jacket  152  surrounding conductor  151 , made of plastic, for example PTFE. Stranded wires  15  are inserted into metal tube  16  at a free end, insulating jacket  152  being held in a sealing grommet  17  that is secured in metal tube  16  in the insertion area of metal tube  16 . In the section of stranded wire that extends between sealing grommet  17  and electrical coupler  13  in detector housing  11 , insulating jacket  152  is removed from stranded wires  15 , so that only bare conductors  151  extend in the hot zone of the internal combustion engine. At the end of metal tube  16  on the detector housing side, a limit stop  18  is positioned in metal tube  16 , through which conductors  151  pass. After conductors  151  pass through, the ends of conductors  151  make contact with electrical coupler  13  in detector housing  11 .  
         [0018]    To insulate conductors  151  electrically from each other and from metal tube  16 , an insulating cover  20  is inserted into metal tube  16 , and conductors  151  are each drawn through one of two tunnels formed in insulating cover  20  and extending for its entire length (FIG. 2). As FIG. 1 illustrates, insulating cover  20  extends from sealing grommet  17  to limit stop  18 , having its particular end faces in contact with these components. In FIG. 2, for the sake of clarity, insulating cover  20  is illustrated with conductors  151  which are enclosed in tunnels  21  pulled part of the way out of metal tube  16 . FIG. 3 again illustrates insulating cover  20  which is visible in FIG. 2, in cross-section (above) and partial top view (below). Insulating cover  20  is formed by a long, thin, flexible strip  22  of an electrically insulating material. Long flexible strip  22  has a middle zone  221  extending the entire length of the strip, and two edge zones  222  adjacent thereto, also extending the entire length of the strip. To form described tunnels  21 , edge zones  222  are turned up onto middle zone  221  so that one edge zone  222  has its free end arranged on middle zone  221  and the other edge zone  222  has its free end arranged on the free end of the edge zone  222  which is turned up onto middle zone  221 . Edge zones  222  are joined with middle zone  221  along a line  23 , which extends at a slight distance from longitudinal edges  223  of edge zones  222  and is indicated in FIG. 3 with a dashed line. It is also possible for the two edge zones  222  to be folded over onto middle zone  221  such that their free ends are arranged on middle zone  221  with their longitudinal edges  223  butting together. In this case, a linear connection  23  is made between each edge zone  222  and middle zone  221 , close to the abutting longitudinal edges  223  of edge zones  222 . For strip  22 , a layer of a textile fabric such as glass silk may be used, which is resistant to high temperatures and has good insulating properties. Such a layer of textile fabric is highly flexible, so that even flattening of metal tube  16 , as illustrated in FIG. 2, as well as extremely small bending of metal tube  16 , is possible. Because of the possibility of flattening and bending metal tube  16 , installation space available for detector  10  may be used optimally. When strip  22  is in the form of a flexible textile fabric, linear connection  23  between edge zones  222  and middle zones  221  is produced by sewing turned-up edge zones  222  onto middle zone  221 .  
         [0019]    If detector  10  is configured as a compact lambda probe, a hookup connection  14  may be necessary in which an electrical connection may be established between coupler  13  in detector housing  10  and the connecting plug using four or five stranded wires  15 , depending on the configuration of the lambda probe. For these cases, insulating cover  20  is merely modified so that it is able to contain the four or five stripped electrical conductors  151 . The remainder of the configuration of hookup connection  14  remains unchanged. FIGS. 4 and 6 illustrate two example embodiments in which insulating cover  20  is implemented with four parallel tunnels  21 .  
         [0020]    In the exemplary embodiment illustrated in FIG. 4, five long, thin, flexible strips  22  of an electrically insulating material are placed one on top of the other and are joined together along a line  23  extending near their longitudinal edges  223 . Subsequent strip  22  which is placed on top of preceding strip  22  has a greater width than the latter, and strips  22  are placed on top of each other such that their longitudinal edges  223  are flush with each other. In this manner the desired tunnels  21  form between strips  22 , the number of tunnels  21  being one less than the number of stacked strips  22 . Thus with the four tunnels  21  desired, as in this case, five strips  22  may be processed in the manner described. Flexible layers of textile fabric of a high-temperature-resistant textile fabric such as glass silk may be used as strips  22 . The linear connections  23  are implemented with sewn seams.  
         [0021]    In the exemplary embodiment illustrated in FIG. 6, to produce the four tunnels  21  in insulating cover  20 , two wide strips  22 , for example layers of textile fabric, may be placed on top of one another and joined together along a plurality of lines  23  extending at lateral intervals from each other. Linear connections  23  are again produced by appropriately sewing the two strips  22 . To obtain four parallel tunnels  21 , a total of five seams or linear connections  23  are necessary. The sections of strips  22  remaining between linear connections  23  are arranged loosely one on top of the other, and may be expanded into a tunnel  21  as each conductor  151  is inserted.  
         [0022]    If tunnels  21  with greater cross-sectional clearance are needed, then one strip  22  may be sewn onto the other strip  22 —as illustrated in FIG. 6—such that the width of the sections of one strip  22  remaining between linear connections  23  is somewhat greater than the lateral spacing of linear connections  23 . As a result, the wave-shaped bulges visible in the cross-sectional view in FIG. 6 form in the strip  22  having the greater width. Together with the other strips  22  which close them, they surround tunnels  21 .  
         [0023]    The implementation of insulating cover  20  with a total of five tunnels  21 , each to receive one conductor  151 , as illustrated in FIG. 5, like insulating cover  20  illustrated in FIG. 6, is made from two wide strips  22  of electrically insulating material. Corresponding to the number of five desired tunnels  21 , the two strips  22  are joined together along a total of six lines  23  extending parallel to each other at the same lateral distance from each other along the entire length of the strip.