Abstract:
A method of fixing a flexible electrical conductor, in which a plurality of flat conductors in which their connecting ends to be connected to another circuit are exposed are integrally covered with a resin-made cladding member, to a fixing portion for connection to the other circuit, comprises the steps of: placing the cladding member on this side of the connecting ends on the fixing portion; and welding together the cladding member on this side of the connecting ends and the fixing portion so as to fix the flexible electrical conductor to the fixing portion. As a result, even if an external force is applied to the flexible electrical conductor, the force is not applied directly to a connecting portion for connecting the connecting ends to connecting ends of the other circuit, thereby improving the electrical reliability in the connection.

Description:
This is a division of application Ser. No. 09/106,044, filed Jun. 29, 1998, U.S. Pat. No. 6,156,138 which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a method of and a structure for fixing a flexible electrical conductor, in which a plurality of electrical conductors are covered with a resin-made cladding member, to a fixing portion for connection to another circuit. 
     FIGS. 1 and 2 respectively show connecting portions  1  and  3  of flat electric wires (flexible electrical conductors) disclosed in Japanese Utility Model Application Laid-Open No. 30723/1991, as well as a flexible electrical conductor  5  connected to the connecting portion  1  or  3 . 
     In the connecting portion  1  shown in FIG. 1, a step portion  7  is formed at a distal end portion, and connecting terminals  9  are exposed on this step portion  7 . A pair of positioning holes  11  are formed at a distal end portion of the step portion  7 . Meanwhile, the flexible electrical conductor  5  connected to this connecting portion  1  is covered with a cladding member  15  in which distal end portions of three flat conductors  13  are exposed. A pair of through holes  17  are formed in an end portion of the cladding member  15 . A pair of fixing pins  21  of a fixing cover  19  are inserted in the through holes  17 . 
     In a case where the flat conductors  13  of the flexible electrical conductor  5  are connected to the connecting terminals  9 , the flexible electrical conductor  5  is placed on the step portion  7 , and after the flat conductors  13  are superposed on the connecting terminals  9 , the fixing pins  21  of the fixing cover  19  are inserted into the through holes  17  and the positioning holes  11 . Next, distal end portions of the fixing pins  21  which passed through the positioning holes  11  and projected to the reverse side are caulked by heating. Consequently, the flexible electrical conductor  5  is nipped by the fixing cover  19  and the step portion  7 , thereby allowing the flat conductors  13  to be electrically connected to the connecting terminals  9 . 
     On the other hand, in the connecting portion  3  shown in FIG. 2, a pair of fixing pins  23  are provided projectingly on a distal end portion of the step portion  7 . When the flexible electrical conductor  5  is placed on the step portion  7 , the fixing pins  23  are inserted into the through holes  17 , and after a fixing cover  25  is placed on top of the flexible electrical conductor  5 , the fixing pins  23  are inserted into a pair of positioning pins  27  in the fixing cover  25 . Next, distal end portions of the fixing pins  23  which projected from the positioning holes  27  of the fixing cover  25  are caulked by heating. Consequently, the flexible electrical conductor  5  is nipped by the fixing cover  25  and the step portion  7 , thereby allowing the flat conductors  13  to be electrically connected to the connecting terminals  9 . 
     In the case where the flexible electrical conductor  5  is connected to the aforementioned connecting portion  1  or  3 , the cladding member  15  is nipped by the fixing cover  19  or  15  and the step portion  7  in which the longitudinal offset is prevented by the fixing pins  21  or  23 , and the flat conductors  13  are electrically connected to the connecting terminals  9 . 
     In the connecting portion  1  or  3 , the positioning of the flat conductors  13  and the connecting conductors is effected by inserting the fixing pins  21  or  23  into the through holes  17 . 
     However, there is a problem in that, in the aforementioned connecting portion  1  or  3 , if the caulked portions of the fixing pins  21  or  23  become loose, play occurs between the fixing cover  19  or  25  and the step portion  7 , and the state of close contact deteriorates, with the result that the electrical reliability in the connection declines. 
     In addition, if a force moving in the axial direction away from the connecting portion  1  or  3  is applied to the flexible electrical conductor  5 , that force is concentrated on the fixing pins  21  or  23 , the force is applied locally to the cladding member  15 . For this reason, there is a possibility that the cladding member breaks. Further, if the force moving in the axial direction away from the connecting portion  1  or  3  is applied, the force is applied directly to the connecting portion  1  or  3 , so that there is a possibility that the flat conductors  13  and the connecting terminals  9  may offset from each other. As a result, the reliability in electrical connection declines. 
     Furthermore, there is a problem in that when the flexible electrical conductor  5  is connected to the connecting portion  1  or  3 , the fixing cover  19  or  25  is required, so that the number of component parts used increases, resulting in higher cost. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a method of and a structure for fixing a flexible electrical conductor which make it possible to prevent the deterioration of the state of close contact between the electrical conductor and connecting terminals of another circuit, which make it possible to prevent an external force, if applied, from being applied directly to the portion connected to a connecting portion of another circuit, and which make it possible to reduce the number of component parts used. 
     To this end, in accordance with a first aspect of the present invention, there is provided a method of fixing a flexible electrical conductor, in which a plurality of flat conductors in which their connecting ends to be connected to another circuit are exposed are integrally covered with a resin-made cladding member, to a fixing portion for connection to the other circuit, comprising the steps of: placing the cladding member on this side of the connecting ends on the fixing portion; and welding together the cladding member on this side of the connecting ends and the fixing portion so as to fix the flexible electrical conductor to the fixing portion. 
     In accordance with the first aspect of the invention, after the cladding member on this side of the connecting ends of the flexible electrical conductor is placed on the fixing portion, the cladding member on this side of the connecting ends and the fixing portion are welded together. As a result, the flexible electrical conductor is fixed to the fixing portion. In this case, since the cladding member on this side of the connecting ends is welded to the fixing portion, an external force applied to the flexible electrical conductor is not transmitted directly to the connecting ends and the connecting portion, with the result that the connecting ends and the connecting ends of another circuit are prevented from offsetting from each other. 
     In accordance with a second aspect of the present invention, in the method of fixing a flexible electrical conductor according to the first aspect of the invention, in which the cladding member on this side of the connecting ends is placed on the fixing portion in close contact therewith, ultrasonic vibrations are applied to the cladding member on this side of the connecting ends and the fixing portion so as to effect welding. 
     In accordance with the second aspect of the invention, in the state in which the cladding member on this side of the connecting ends is placed on the fixing portion in close contact therewith, ultrasonic vibrations are applied to the cladding member on this side of the connecting ends and the fixing portion. Consequently, the cladding member and the fixing portion are welded together, thereby allowing the flexible electrical conductor to be fixed to the fixing portion. 
     In accordance with a third aspect of the present invention, in the method of fixing a flexible electrical conductor according to the first or second aspect of the invention, an irregular surface portion is provided on the fixing portion along a direction perpendicular to a longitudinal direction of the flat conductors. 
     In accordance with the third aspect of the invention, the cladding member on this side of the connecting ends is placed on the irregular surface portion provided on the fixing portion along a direction perpendicular to the longitudinal direction of the flat conductors, and this irregular surface portion and the cladding member are welded together. In this case, by virtue of the provision of the irregular surface portion on the fixing portion, the area of contact between the cladding member and the fixing portion becomes large. 
     In accordance with a fourth aspect of the present invention, in the method of fixing a flexible electrical conductor according to any one of the first to third aspects of the invention, in state in which the plurality of flat conductors which are elongated are arranged planarly substantially planarly at predetermined intervals, the flexible electrical conductor is covered with the resin-made cladding member. 
     In accordance with the fourth aspect of the invention, since the resinous cladding member which covers the plurality of flat conductors arranged planarly substantially in parallel at predetermined intervals is welded to the fixing portion, the flexible electrical conductor is fixed to the fixing portion. In this case, even if an external force is applied to the flexible electrical conductor along its longitudinal direction, the external force is applied to the overall welded portion of the welded cladding member, and the force is not applied directly to the connecting portion correcting the conductors and the other circuit. 
     In accordance with a fifth aspect of the present invention, there is provided a structure for fixing a flexible electrical conductor, in which a plurality of flat conductors in which their connecting ends to be connected to another circuit are exposed are integrally covered with a resin-made cladding member, to a fixing portion for connection to the other circuit, wherein the cladding member on this side of the connecting ends is welded to the fixing portion. 
     In accordance with the fifth aspect of the invention, the cladding member on this side of the connecting ends is welded to the fixing portion so as to fix the flexible electrical conductor to the fixing portion. 
     In accordance with a sixth aspect of the present invention, in the structure for fixing a flexible electrical conductor according to the fifth aspect of the invention, an irregular surface portion is provided on the fixing portion. 
     In accordance with the sixth aspect of the invention, since the irregular surface portion is provided on the fixing portion, the welding area between the cladding member on this side of the connecting ends and the fixing portion becomes large. 
     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view illustrating a conventional method of and a structure for fixing a flexible electrical conductor; 
     FIG. 2 is a perspective view illustrating a another conventional method of and a structure for fixing a flexible electrical conductor; 
     FIGS.  3 ( a ) and  3 ( b ) are diagrams illustrating a first embodiment of a method of fixing a flexible electrical conductor in accordance with the present invention, in which 
     FIG.  3 ( a ) is a perspective view of the flexible electrical conductor and a fixing portion, and FIG.  3 ( b ) is a cross-sectional view thereof; 
     FIG. 4 is an exploded perspective view illustrating a fixing portion and a flexible electrical conductor which is fixed to the fixing portion in a second embodiment of the method of fixing a flexible electrical conductor in accordance with the present invention; 
     FIG. 5 is a plan view illustrating the fixing portion and the flexible electrical conductor which is fixed to the fixing portion in accordance with the second embodiment; and 
     FIG. 6 is a cross-sectional view illustrating the fixing portion and the flexible electrical conductor which is fixed to the fixing portion in accordance with the second embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the accompanying drawings, a description will be given of embodiments of the structure for a method of fixing a flexible electrical conductor in accordance with the present invention. 
     First Embodiment 
     FIGS.  3 ( a ) and  1 ( b ) show a flexible electrical conductor  29  and a fixing portion  31  made of PBT (polybutylene terephtalate) or the like in accordance with a first embodiment. FIG.  3 ( a ) is a perspective view of the flexible electrical conductor  29  and the fixing portion  31  to which this flexible electrical conductor  29  is fixed, while FIG.  3 ( b ) is a cross-sectional view illustrating a state in which the flexible electrical conductor  29  is welded to the fixing portion  31 . 
     As shown in FIGS.  3 ( a ) and  3 ( b ), the flexible electrical conductor  29  is arranged such that three elongated flat conductors  33  are arranged planarly substantially parallel to each other at predetermined intervals, and are covered with a resin-made cladding member  35 . Distal end portions of the flat conductors  33  are exposed to form connecting terminals  37 . These connecting terminals  37  are connected to connecting terminals  39  of another circuit. The cladding member  35  on this side of the connecting terminals  37  is formed as a welding portion  41  which is welded to the fixing portion  31 . 
     The fixing portion  31  has an irregular surface portion  43  in which a serrated formation is arranged along a direction perpendicular to the longitudinal direction of the flat conductors  33  (the axial direction of the fixing portion  31 ). This irregular surface portion  43  is comprised of four angular edges  45  and notches  47  provided between adjacent ones of the angular edges  45  and on outer sides of the outermost angular edges  45 . In the state in which the welding portion  41  is welded onto the fixing portion  31 , the flat conductors  33  are superposed on the connecting terminals  39  of the other circuit in contact therewith, and are electrically connected thereto. 
     Next, a description will be given a method of fixing the flexible electrical conductor  29  to the fixing portion  31 . 
     First, after the welding portion  41  on this side of the connecting terminals  37  is placed on the fixing portion  31 , the welding portion  41  and the fixing portion  31  are welded to each other. In this case, in which the edges  45  of the irregular surface portion  43  abut against the cladding member  35  between the flat conductors  33 , the welding portion  41  and the fixing portion  31  are welded to each other by applying heat or ultrasonic vibrations to the fixing portion  31  and the cladding member  35 . In this case, since the welding portion  41  is welded in close contact with the irregular surface portion  43 , the welding portion  41  also assumes a serrated form. Thus the flexible electrical conductor is fixed to the fixing portion  31 . In this state, the connecting terminals  37  are superposed in close contact with the connecting terminals  39  of the other circuit, and are electrically connected thereto. 
     In accordance with this embodiment, since the welding portion  41  is welded directly to the fixing portion  31 , the connecting terminals  37  and the connecting terminals  39  of the other circuit are superposed on top of each other in close contact. In addition, an external force applied to the flexible electrical conductor  29  is not transmitted to the portion connecting the connecting terminals  37  and the connecting terminals  39  of the other circuit. Further, since the external force applied to the flexible electrical conductor is not applied locally to the cladding member  35 , the cladding member does not break. Accordingly, it is possible to improve the electrical reliability in t he connection. 
     Further, since the welding portion  41  of the cladding member  35  is welded directly to the fixing portion  31 , the state of close contact between the connecting terminals  37  and the connecting terminals  39  of the other circuit does not deteriorate. 
     Furthermore, in this embodiment, since the fixing portion  31  is provided with the irregular surface portion  43 , and the cladding member  35  is welded directly to this irregular surface portion  43 , it is possible to secure a large welded area without enlarging the width of the fixing portion  31 . Therefore, the welding portion  41  can be fixed more firmly to the fixing portion  31 . 
     That is, although if the fixing portion  31  is planar, an area for welding the welding portion  41  of the cladding member  35  is required by the portion of the widthwise length of the flexible electrical conductor  29 , the width of the fixing portion  31  can be made shorter than the width of the flexible electrical conductor  29  by providing the irregular surface portion  43 . 
     Further, since the irregular surface portion  43  is provided along the widthwise direction of the fixing portion  31 , even if an external force is applied in the widthwise direction, the flexible electrical conductor  29  is difficult to be offset in the widthwise direction, so that the connecting terminals  37  are not offset from the connecting terminals  39  of the other circuit. 
     Further, since it is unnecessary to fix the flexible electrical conductor  29  by means of a fixing plate in the conventional manner, the number of component parts used can be reduced, thereby making it possible to lower the manufacturing cost. 
     Second Embodiment 
     Next, a description will be given of a second embodiment. This second embodiment is a fixing method which is used in fixing a terminal portion of a flexible electrical conductor  49  arranged between a steering wheel and a steering shaft of an automobile to a cable reel (not shown). FIG. 4 is a exploded perspective view illustrating a terminal fixing member  51  for fixing terminals of the cable reel as well as the flexible electrical conductor  49  which is fixed to the terminal fixing member  51 . 
     As shown in FIG. 3, the terminal fixing member  51  is formed in an arcuate shape in terms of its overall configuration, and a retaining portion  53  for retaining connecting terminals (not shown) of another circuit is provided at a distal end portion thereof. The retaining portion  53  has three rectangular hole portions  55  formed in such a manner as to penetrate the terminal fixing member  51  from its obverse side to its reverse side. The connecting terminals  37  of the flexible electrical conductor  49  are placed on these hole portions  55 . A fixing portion  57  for fixing the flexible electrical conductor  49  is formed on this side of the retaining portion  53 . 
     The fixing portion  57  has an irregular surface portion  61  formed on a planar upper surface  59 . The irregular surface portion  61  is comprised of a pair of angular projections  63  provided on transverse opposite sides of the fixing portion  57  in such a manner as to project from the upper surface  59 , as well as a pair of notched projections  65  arranged at equal intervals between the pair of angular projections  63  and each having a substantially M-shaped outer configuration in terms of its cross section. The two projecting edges of each of the pair of notched projections  65  are also formed as a pair of angular projections  63 , and recessed portions  67  are formed on transverse opposite sides of the fixing portion  57  and between adjacent ones of all the angular projections  63 . Furthermore, as shown in FIGS. 5 and 6, the welding portion  41  of the flexible electrical conductor  49  is welded to the irregular surface portion  61 . In this case, as shown in FIG. 5, the welding portion  41  is welded to the fixing portion  57  by thermal welding or ultrasonic vibration welding such that the angular projections  63  are respectively positioned at portions of the cladding member  35  that are located between the flat conductors  33  and on outer sides of the outermost flat conductors  33 . 
     It should be noted that, in FIG. 4, reference numeral  69  denotes a cover for covering the retaining portion  53  and the fixing portion  57 . This cover  69  does not serve to fix the flexible electrical conductor  49  to the fixing portion  57 , but merely covers the retaining portion  53  and the fixing portion  57  from the outside. 
     To fix the flexible electrical conductor  49  to the fixing portion  57 , the welding portion  41  of the flexible electrical conductor  49  is first placed on the fixing portion  57 . In this state, the exposed connecting terminals  37  are located above the hole portions  55  of the retaining portion  53 . Next, by applying heat or ultrasonic vibrations to the irregular surface portion  61  and the welding portion  41 , the welding portion  41  is welded to the fixing portion  57 , as shown in FIG.  6 . As a result, the flexible electrical conductor  49  is fixed to the fixing portion  57 . 
     In accordance with this embodiment, since the fixing portion  57  is welded directly to the welding portion  41 , an external force applied to the flexible electrical conductor  49  is not transmitted directly to the connecting portion for connecting the connecting terminals  37  and the connecting terminals of the other circuit. Consequently, it is possible to improve the electrical reliability in the connection. 
     In addition, since it is unnecessary to fix the flexible electrical conductor  49  by means of a fixing plate in the conventional manner, the number of component parts used can be reduced, thereby making it possible to lower the manufacturing cost. 
     It should be noted that in a case where the welding portion  41  and the fixing portion  57  are welded together, the welding portion  41  and the fixing portion  57  may be welded together by a method other than welding by using heat or welding by using ultrasonic vibrations. 
     While there has been described in connection with the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the invention.