Abstract:
A terminal fitting ( 10 ) includes a main body ( 20 ) to be coupled to a mating conductor, and a crimp contact section ( 30 ) rearward from the main body ( 20 ). The crimp contact section ( 30 ) is crimped on an end of a core wire ( 42 ) in a covered electrical cable ( 40 ) so as to surround the end. The core wire ( 42 ) includes a plurality of metallic strands ( 41 ) and is covered with a sheath ( 43 ) to form the covered electrical cable ( 40 ). Serrations ( 34 ) are provided on a contact surface of the crimp contact section ( 30 ) for surrounding the core wire ( 42 ). Each serration ( 34 ) is a polygonal shaped recess with which the core wire ( 42 ) engages upon crimping. Both diagonal corner portions ( 34 C) of each serration ( 34 ) are rounded. Thus, the whole periphery of an opening edge around the recess penetrates an oxide layer on a core wire.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to an insulation displacement terminal, a splicing terminal assembly, and a press-contact structure for an electric cable. 
         [0003]    2. Description of the Related Art 
         [0004]    Heretofore, for example an insulation displacement terminal has been utilized as a splicing terminal assembly for branching a branched line from a main line and connecting the branched line to the main line or a jointing terminal assembly for connecting a plurality of electrical cables (see, for example, JP HEI 10 (1998)-275639 A. 
         [0005]    The insulation displacement terminal is formed by pressing a metallic plate having high electrical conductivity. The insulation displacement terminal includes a press-contact blade provided with a press-contact groove. A covered electric cable in which a conductive core wire is covered with an insulation sheath is pushed into the press-contact groove. When the covered electric cable is pushed into the press-contact groove in the press-contact blade, the insulation sheath is broken by groove edges to expose the core wire. When the exposed core wire contacts with the groove edges, they are electrically connected. 
       SUMMARY OF THE INVENTION 
       [0006]    Currently, even in a field of a wire harness for a motor vehicle, an aluminium electric cable has been used in order to reduce a weight of the covered electric cable. The aluminium electric cable includes a core wire comprising a plurality of aluminium or aluminium alloy strands and an insulation sheath covering the core wire. On the other hand, in such a kind of aluminium electric cable, if the core wire is exposed to outside air, an oxide layer is likely to be generated on a surface of the core wirer. There is a possibility that the oxide layer will be generated on the surface of the core wire at a producing stage of the covered electric cable. 
         [0007]    Accordingly, in the case where the covered electric cable to be pushed into the insulation displacement terminal is the aluminium electric cable, when the core wire exposed by breaking, the insulation sheath contacts with groove edges of the press-contact groove, the core wire is electrically connected through the oxide layer on the core wire to the press-contact groove, so that an electrical resistance will be increased. 
         [0008]    In the case of another electric cable (for example, a copper electric cable) except the aluminium electric cable, there is a possibility that a few oxide layer will be generated on the surface of the core wire. Consequently, there is a problem that an electrical resistance will be increased in a press-contact portion between the core wire and the insulation displacement terminal, as is the case with the aluminium electric cable. 
         [0009]    In view of the above problems, an object of the present invention is to prevent a portion of a covered electric cable pressed onto the press-contact blade of the insulation displacement terminal from increasing an electrical resistance. 
         [0010]    An insulation displacement terminal of the present invention comprises: a press-contact blade; and a stripping section provided on at least one of groove edges of a press-contact groove in the press-contact blade. The press-contact blade includes the press-contact groove into which a covered electric cable covered with an insulation sheath around a conductive core wire can be pushed. When the covered electric cable is pushed into the press-contact groove, the insulation sheath is broken to expose the core wire, so that the exposed core wire is brought into press-contact with the groove edges of the press-contact groove and is electrically coupled to the groove edges. The stripping section is adapted to slide on a surface of the exposed core wire. 
         [0011]    A press-contact structure for an electric cable in accordance with the present invention is characterized in that a covered electric cable in which an insulation sheath covers an electrically conductive core wire is press-connected to the above insulation displacement terminal. 
         [0012]    According to the above construction, since both groove edges of the press-contact groove breaks the insulation sheath when the covered electric cable is pushed into the press-contact groove in the press-contact blade, the core wire is exposed. Since the stripping section slides on the surface of the core wire, the oxide layer generated on the surface of the core wire is stripped and the emergent surface of the core wire contacts with the groove edges of the press-contact groove. Thus, an electrical resistance in the contact portion between the core wire and the press-contact blade (that is, the press-contact portion of the covered electric cable) is kept to be lower, thereby enhancing an electrical performance. 
         [0013]    The insulation displacement terminal may include the following structures. 
         [0014]    (1) When the insulation sheath is broken and then the stripping section slides on the surface of the exposed core wire, the stripping section strips a layer generated on the surface of the core wire, and an emergent surface on the core wire is brought into contact with the groove edges of the press-contact groove. 
         [0015]    (2) The stripping section is provided on only longitudinal areas on the groove edges of the press-contact groove at an upstream side in a pushing direction of the covered electric cable. 
         [0016]    In an initial pushing stage of the covered electric cable, the stripping section slides on the surface of the core wire to strip the oxide layer on the core wire. In a final pushing stage of the covered electric cable, the groove edges of the press-contact groove, on which the stripping section is not provided, slide on the surface of the core wire. Consequently, a pushing resistance in the final pushing stage is kept to be lower and a pushing force becomes small, as a whole. In the finishing stage of pushing, since the emergent surface on the core wire contacts with the areas of the groove edges on which the stripping section is not provided, it is possible to make a contact area great. 
         [0017]    (3) The stripping section is provided on longitudinal areas on the groove edges of the press-contact groove at an upstream side in a pushing direction of the covered electric cable and on inner longitudinal areas on the groove edges of the press-contact groove at a position corresponding to a finished pushing position of the covered electric cable. 
         [0018]    If a portion of the covered electric cable that is press-contacted with the insulation displacement terminal is located under a hard condition in which cooling and heating actions are repeated on account of a mounting position of a wire harness or the like, the core wire repeats contraction and expansion. In particular, when the core wire is contracted, a gap is caused between the core wire and the groove edges of the press-contact groove, thereby involving a possibility that another contact resistance may be generated. 
         [0019]    On the contrary, according to the above construction, the stripping section bites the surface of the core wire at the finished stage of pushing. Consequently, a contacting condition between the stripping section and the core wire can be maintained positively even at the contraction of the core wire, thereby preventing the contact resistance from being generated. 
         [0020]    (4) The stripping section is a stripping tooth section in which a plurality of teeth having sharply angled crest-like shape are juxtaposed in the pushing direction of the covered electric cable. Since a sharply angled distal end of each tooth that constitutes the stripping tooth section slides on the surface of the core wire in sequence, it is possible to effectively strip the oxide layer. 
         [0021]    (5) Each tooth that constitutes the stripping tooth section is formed into a crest-like shape having a gentle slope at an upstream side in the pushing direction of the covered electric cable and a steep slope at a downstream side in the pushing direction. Since the gentle slope of the crest-like shape of each stripping tooth section contacts with the covered electric cable in sequence when the cable is pushed into the press-contact groove, the pushing resistance is kept to be lower. After finishing the pushing step, since the steep slope of each stripping tooth section engages the cable, the cable hardly comes out of the press-contact groove. 
         [0022]    (6) The stripping section is provided with an originally cut surface to which a surface treatment of plating is not applied. The originally cut surface, to which the surface treatment of plating is not applied, is rough serrated surface. Since the rough serrated surface slide on the surface of the core wire in sequence, the oxide layer is stripped. 
         [0023]    Furthermore, the splicing terminal assembly and the press-contact structure for an electric cable may include the following structures. 
         [0024]    (7) A crimp terminal to be connected by crimping to an end of another covered electric cable in which an insulation sheath covers an electrically conductive core wire is connected to the above insulation displacement terminal to form the splicing terminal assembly. According to the splicing terminal assembly, in the case where a branched line is made from the main line, an intermediate position of the main line is press-contacted to the insulation displacement terminal. On the other hand, an end of the branched line can be crimped on the crimp terminal. 
         [0025]    (8) A covered electric cable in which an insulation sheath covers an electrically conductive core wire is press-connected to the above insulation displacement terminal in the splicing terminal assembly. 
         [0026]    (9) The covered electric cable is an aluminium electric cable in which an insulation sheath covers a core wire comprising a plurality of aluminium or aluminium alloy strands. This is particularly effective for the aluminium electric cable that is likely to generate an oxide layer on a surface of the core wire. 
         [0027]    According to the present invention, it is possible to prevent the portion of the covered electric cable press-contacted on the press-contact blade of the insulation displacement terminal to increase an electrical resistance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a perspective view of a first embodiment of a splicing terminal assembly in accordance with the present invention. 
           [0029]      FIG. 2  is a plan view of the splicing terminal assembly shown in  FIG. 1 , illustrating the splicing terminal assembly on which a copper electric cable are crimped. 
           [0030]      FIG. 3  is a plan view of the splicing terminal assembly shown in  FIG. 2 , illustrating the splicing terminal assembly equipped with the copper electric cable and mounted on a housing main body. 
           [0031]      FIG. 4  is a front elevation view of a first embodiment of an insulation displacement terminal in accordance with the present invention, illustrating an aluminum electric cable under a condition before being press-contacted with the insulation displacement terminal. 
           [0032]      FIG. 5  is a front elevation view of the insulation displacement terminal shown in  FIG. 4 , illustrating the aluminium electric cable under an initial press-contact condition. 
           [0033]      FIG. 6  is a front elevation view of the insulation displacement terminal shown in  FIG. 4 , illustrating the aluminium electric cable under a completed press-contact condition. 
           [0034]      FIG. 7  is a front elevation view of a part of a press-contact blade of the insulation displacement terminal in the first embodiment. 
           [0035]      FIG. 8  is an enlarged front elevation view of a stripping tooth section of the press-contact blade shown in  FIG. 7 . 
           [0036]      FIG. 9  is a front elevation view of a part of a press-contact blade of the insulation displacement terminal in a second embodiment. 
           [0037]      FIG. 10  is a front elevation view of a part of a press-contact blade of the insulation displacement terminal in a third embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    Referring now to the drawings, embodiments of a splicing terminal assembly in accordance with the present invention will be described below. 
       First Embodiment 
       [0039]      FIGS. 1 to 8  show a first embodiment of a splicing terminal assembly  20  in accordance with the present invention. 
         [0040]    The first embodiment illustrates a case where a main line such as an electrical power sourced line is branched into and connected to a signal line for an air bag system or the like. An insulation displacement terminal  30  according to the present invention is applied to a part of the splicing terminal assembly  20  suitable for branching connection. 
         [0041]    The main line uses an aluminium electric cable  10 . As shown in  FIG. 4 , the aluminium electric cable  10  includes a core wire  11  formed by a plurality of strands made of aluminium or aluminium alloy. The core wire  11  is covered with a synthetic resin insulation sheath  13 .  FIGS. 4 to 6  show schematically a cross section of the core wire  11  comprising a plurality of aluminium strands, as a whole. 
         [0042]    A branched line uses a copper electric cable  15 . As shown in  FIG. 2 , the copper electric cable  15  includes a core wire  16  formed by a plurality of copper alloy strands  17 . The core wire  16  is covered with a synthetic resin insulation sheath  18 . 
         [0043]    The splicing terminal assembly  20  is formed by pressing a metallic plate (for example, a copper or copper alloy plate) and is plated with tin (Sn). As shown in  FIGS. 1 and 2 , the insulation displacement terminal  30  and a crimp terminal  40  are laterally arranged and connected to each other. 
         [0044]    An end of the branched copper electric cable  15  is connected to the crimp terminal  40 . The crimp terminal  40  includes a wire barrel  41  and an insulation barrel  42  connected to the wire barrel  41  at a front side. 
         [0045]    The wire barrel  41  is caulked and pressed onto an end of the core wire  16  exposed by removing an insulation sheath  18  from the copper electric cable  15 . The wire barrel  41  includes a pair of wide barrel pieces  41 A that stand up from right and left edges of a bottom plate  43  to be opposed to each other. Both barrel pieces  41 A are confronted to each other so that the barrel pieces  41 A surround an outer periphery of the end of the core wire  16  at both sides, and are caulked onto the end in a so-called heart-like shape. 
         [0046]    The insulation barrel  42  is caulked and pressed onto an end of the remained insulation sheath  18 . The insulation barrel  42  includes a pair of right and left barrel pieces  42 A provided on right and left side edges of the bottom plate  43  and projected upward to be shifted from each other in a back-and-forth direction. Each barrel piece  42 A is narrower and higher than each barrel piece  41 A. Projecting ends of both barrel pieces  42 A are overlapped on each other in the back-and-forth direction so that the both barrel pieces  42 A surround an outer periphery of an end of the insulation sheath  18  in the right and left direction to be caulked onto the end. 
         [0047]    The wire barrel  41  is provided on an inner part with a connecting section  44  that projects upright from an inner side of the bottom plate  43 . 
         [0048]    A mid position of the main line aluminium electric cable  10  in its longitudinal direction is connected to the insulation displacement terminal  30 . The terminal  30  includes a base plate  31  extending in a back-and-force direction and a pair of press-contact blades  32  each projecting upright from each of front and back ends of the base plate  31 . Each press-contact blade  32  is provided in a central part in its width direction with a press-contact groove  33  that is open at an upper edge. The press-contact groove  33  is provided on its upper end or its inlet port with a guide portion  35  that is tapered downward. A size in width of the press-contact groove  33  is set to be smaller than a diameter of the core wire  11  in the aluminium electric cable  10 . A size in depth of the press-contact groove  33  is set to be about 1.5 times the diameter of the aluminium electric cable  10 . 
         [0049]    The crimp terminal  40  and insulation displacement terminal  30  constructed above are arranged and spaced apart from each other by a given distance in a right and left direction. An elongated connecting plate  22  is bridged between a inner part of the connecting section  44  of the crimp terminal  40  and a left side lower end of the press-contact blade  32  at the inner part in the insulation displacement terminal  30 , thereby forming the splicing terminal assembly  20  in which the crimp terminal  40  and insulation displacement terminal  30  are integrated. 
         [0050]    As shown in  FIG. 3 , a housing  50  contains the splicing terminal assembly  20  constructed above. The housing  50  is made of synthetic resin. The housing  50  includes a housing main body  51 , a cover  52  mounted on an upper surface of the housing main body  51  at its side position, and a hinge  53  coupling the cover  52  to the housing main body  51 . 
         [0051]    The housing main body  51  on right and left sides with two mounting recesses  56  and  55 . The left side (a side provided with the hinge  53 ) mounting recess  55  is adapted to receive the crimp terminal  40  caulked and crimped on the end of the copper electric cable  15 . In particular, the crimp terminal  40  is positioned and fitted in the mounting recess  55  so that the terminal  40  cannot move in the back-and-forth direction. The left side mounting recess  55  is provided on its front side with a cable support section  57  that receives a lower surface of the copper electric cable  15  drawn out of the crimp terminal  40 . 
         [0052]    On the other hand, the right side mounting recess  56  receives a bottom part of the insulation displacement terminal  30 . Specifically, the bottom part of the insulation displacement terminal  30  is tightly fitted in the recess  56  so that the terminal  30  cannot move in the back-and-forth direction and in the right and left direction. The right side mounting recess  56  is provided on its front side and back side with cable support sections  58  that receive a lower surface of the aluminium electric cable  10  drown out of the front and back sides of the insulation displacement terminal  30 . 
         [0053]    The housing main body  51  is provided with a mounting groove in which a lower part of the connecting plate  22  is tightly fitted to interconnect the inner parts of the right and left mounting recesses  56  and  55  to each other. 
         [0054]    The cover  52  is attached to the upper surface of the housing  50  so that the cover  52  is turned inside out from the state shown in  FIG. 3 , while the hinge  53  is being bent rightward. The cover  52  is locked on a regular positioned by a locking mechanism (not shown). Although a part of the cover  52  is omitted in  FIG. 3 , the cover  52  is provided with a mounting recess  60  and a cable support section  61 . The mounting recess  60  is fitted on an upper surface side of the crimp terminal  40  caulked on the end of the copper electric cable  15 . The cable support section  61  clamps the upper surface of the copper electric cable  15  drawn out to the front side from the crimp terminal  40  between the section  61  of the cover  52  and the cable support section  57  of the housing main body  51 . 
         [0055]    As shown in  FIG. 6 , the cover  52  is provided with a holding section  63  and a cable support section (not shown). The holding section  63  extends to reach the aluminium electric cable  10  inserted into a regular position (mentioned after) in the insulation displacement terminal  30  in a space between the front and back press-contact blades  32 , when the cover  52  is mounted on the housing main body  51  at a regular position, as shown by chain lines in  FIG. 6 . The cable support section (not shown) clamps an upper surface of the aluminium electric cable  10  drawn out of the front and back sides of the insulation displacement terminals  30  between the cable support section and the cable support section  58  of the housing main body  51 . 
         [0056]    The front and back press-contact blades  32  of the insulation displacement terminal  30  that constitutes the splicing terminal assembly  20  are provided with stripping tooth section  70  (corresponding to a stripping section in the present invention) that serves to strip an oxide layer formed on a surface of the core wire  11  in the aluminium electric cable  10 . 
         [0057]    Specifically, as shown in  FIG. 7 , the stripping tooth section  70  is provided on its upper half part (near the guide section  35 ) of each of right and left groove edges  34  on the press-contact groove  33  in each press-contact blade  32 . The stripping tooth section  70  includes a plurality of teeth  71  arranged in an upper and lower direction. Essentially, each tooth  71  is formed into a sharply angled crest-like shape. As shown in  FIG. 8 , an upper side gentle slope  72  of the tooth  71  has an slant angle α (alpha) of less than 45 degrees (for example, 30 degrees) with respect to a longitudinal direction of the press-contact groove  33  while a lower side steep slope  73  has an slant angle β (beta) of more than 45 degrees (for example, 60 degrees). 
         [0058]    Next, an operation of the splicing terminal assembly in the first embodiment will be described below. 
         [0059]    An example of a splicing work will be described as follow. Firstly, an end of the branched copper electric cable  15  is connected to the crimp terminal  40  of the splicing terminal assembly  20 . An end of the insulation sheath  18  is stripped from the copper electric cable  15  to expose a given length of an end of the core wire  16 . On the other hand, the splicing terminal assembly  20  is set on a crimp machine equipped with an anvil and a crimper. The end of the exposed core wire  16  is disposed on the wire barrel  41  of the crimp terminal  40  while an end of the remained insulation sheath  18  is disposed on the insulation barrel  42  of the terminal  40 . Both barrels  41  and  42  are clamped between the anvil and the crimper to be caulked. Thus, as shown in  FIG. 2 , the wire barrel  41  is caulked on the end of the core wire in a hear-like shape while the insulation barrel  42  is caulked on the end of the insulation sheath  18  so as to be overlapped in the back-and-forth direction. In other words, the crimp terminal  40  of the splicing terminal assembly  20  is connected to the branched copper electric cable  15 . 
         [0060]    As described above, the splicing terminal assembly  20  connected to the end of the copper electric cable  15 , as shown in  FIG. 3 , is mounted on the housing main body  51  of the housing  50  which is at an open position. Specifically, the bottom portion of the insulation displacement terminal  30  in the splicing terminal assembly  20  is tightly fitted into the right side mounting recess  56 , the lower portion of the connecting plate  22  is fitted into the mounting groove  59 , and the crimp terminal  40  caulked on the end of the copper electric cable  15  is attached to the left side mounting recess  55 . The copper electric cable  15  drawn out of the crimp terminal  40  is received in the cable support section  57 . 
         [0061]    Thus, although it is not described in detail, the splicing terminal assembly  20  connected to the end of the copper electric cable  15  is set on a lower die of the insulation displacement machine. Then, as shown by chain lines in  FIG. 3 , a mid portion of the main line aluminium electric cable  10  in the longitudinal direction is disposed above the insulation displacement terminal  30  in the splicing terminal assembly  20 . Thereafter, an upper die of the insulation displacement machine is moved down and a pushing section of the upper die pushes down the aluminium electric cable into a pace between both press-contact blades  32  and spaces outside the press-contact blades  32 , as shown by an arrow in  FIG. 4 . 
         [0062]    Thus, the aluminium electric cable  10  is pushed into the press-contact grooves  33  in the corresponding press-contact blades  32  of the insulation displacement terminal  30  at given two front and back side positions of the cable  10 . The aluminium electric cable  10  is pushed into the press-contact grooves  33  while the cable  10  is being guided by the guide portion  35 , and the insulation sheath  13  is broken by upper sharp distal ends  33 A of the press-contact grooves  33 . Thus, the exposed core wire  11  is pushed into the press-contact grooves  33  while the exposed core wire  11  is contacting with the groove edges  34  on the press-contact grooves  33 . 
         [0063]    In particular, in the aluminium electric cable  10 , the core wire  11  comprising the aluminium strands is likely to generate an oxide layer on the surface of the core wire  11 . There is a possibility of generating the oxide layer on the surface of the core wire  11  at the initial step of producing the aluminium electric cable  10 . Accordingly, if the groove edges  34  of the press-contact grooves  33  are smooth, the oxide layer on the surface of the exposed core wire  11  slides down on the groove edges  34  when the core wire  11  is pushed down in the press-contact grooves  33 . Consequently, there is a possibility that the oxide layer will remains on the surface of the core wire without being stripped. Then, the aluminium electric cable  10  and press-contact blades  32  may be connected to each other under a condition where the oxide layer is interposed between them, thereby increasing an electrical resistance. 
         [0064]    On the contrary, in the first embodiment, since the right and left groove edges  34  of the press-contact groove  33  of each press-contact blade  32  is provided on a substantially upper half part near the guide portion  35  with the stripping tooth section  70 , as shown in  FIG. 5 , the insulation sheath  13  of the aluminium electric cable  10  is broken to expose the core wire  11 , the exposed core wire  11  is pushed down into the press-contact grooves  33 , and the stripping tooth section  70  contacts with the surface of the core wire  11 . Specifically, the sharp distal end of each tooth  71  that constitutes the stripping tooth section  70  contacts with the surface of the core wire  11  in sequence, thereby stripping the oxide layer generated on the surface of the core wire  11 . 
         [0065]    As shown in  FIG. 6 , when the aluminium electric cable  10  is pushed down into the regular position in the press-contact grooves  33 , an emergent surface formed on the surface of the core wire  11  by stripping the oxide layer will contact with lower side smooth areas on both groove edges  34  of each press-contact groove  33 . 
         [0066]    After a regular press-contact work for the aluminium electric cable  10  has been finished, as described above, the upper die of the press-contact machine is retracted upward, and the cover is turned inside out while bending the hinge  53  so that the cover is mounted and locked on the housing main body  51 . In connection with this step, a holding portion  63  of the cover  52  moves to a position directly above the aluminium electric cable  10 , and the cable  10  is held at the regular press-contact position. Then, the housing  50  incorporated with the splicing terminal assembly  20  is taken from the press-contact machine. Thus, a work of connecting the branched copper electric cable  15  to the main line aluminium electric cable  10  has been completed. In this case, the emergent surface caused by removing the oxide layer from the surface of the core wire  11  at the portion of the aluminium electric cable  10  that is brought into press-contact with the insulation displacement terminal  30  contacts with the groove edges  34  of the press-contact grooves  33  of the insulation displacement terminal  30 , thereby decreasing an electrical resistance and enhancing an electrical performance. 
         [0067]    According to the first embodiment constructed above, in the insulation displacement terminal  30  with which the aluminium electric cable  10  is press-contacted, since the stripping tooth section  70  comprising a plurality of teeth  71  having sharply angled crest-like shapes are provided on both groove edges  34  of the press-contact grooves  33  in the press-contact blades  32 , the stripping tooth section  70  breaks the insulation sheath  13  while the aluminium electric cable  10  is pushed into the press-contact grooves  33  in the press-contact blades  32 , the stripping tooth section  70  slides on the exposed core wire  11 , so that the oxide layer generated on the surface of the core wire  11  is stripped. Consequently, the emergent surface on the core wire  11  contacts with the groove edges  34  of the press-contact grooves  33 . Thus, a contacting part between the core wire  11  and the press-contact blades  32  (that is, a press-contacted portion on the aluminium electric cable  10 ) will lower its electrical resistance and enhance an electrical performance. 
         [0068]    In the first embodiment, the stripping tooth section  70  are formed only a substantially half area at the inlet port in the groove edges  34  of the press-contact grooves  33 . Accordingly, at the initial step of pushing the aluminium electric cable  10 , the stripping tooth section  70  slide on the surface of the core wire  11  to strip the oxide layer. At the final step of pushing the cable  10 , the area of the groove edges  34  having no stripping tooth section  70  slides on the surface of the core wire  11 . Thus, a pushing resistance at the final pushing step is kept to be small, thereby decreasing the pushing force, as a whole. At the finished step of pushing the cable  10 , since the emergent surface of the core wire  11  contacts with the area of the groove edges  34  of the press-contact grooves  33  having no stripping tooth section  70 , it is possible to increase the contact area, thereby enhancing reliability in electrical connection. 
         [0069]    The stripping tooth  70  includes the tooth  71  having the sharply angled crest-like shape. A plurality of teeth  71  are arranged in a pushing direction (in an upper and lower direction) of the aluminium electric cable  10 . In each tooth  71  of the stripping tooth section  70 , a front side (upstream side in the pushing direction of the cable  10 ) slope  72  is gentle and an inner side (downstream side) slope  73  is steep. 
         [0070]    Accordingly, when the exposed core wire  11  in the aluminium electric cable  10  is pushed down along the press-contact grooves  33 , the sharply angled crest-like distal end of each tooth  71  that constitutes the stripping tooth section  70  slides on the surface of the core wire  11  in sequence, so that the oxide layer generated on the surface of the core wire  11  is positively stripped. 
         [0071]    When the exposed core wire  11  in the aluminium electric cable  10  is pushed down along the press-contact grooves  33 , the gentle slope  72  of the sharply angled crest-like distal end of each tooth  71  slides on the surface of the core wire  11  in sequence, so that the pushing resistance is kept to be lower, and after finishing the pushing step, the core wire  11  contacts with the steep slope  73 , so that the core wire  11  is hardly drawn out of the press-contact grooves  33 . 
       Second Embodiment 
       [0072]    A second embodiment of the splicing terminal assembly  20  in accordance with the present invention will be described below by referring to  FIG. 9 . 
         [0073]    As described in the first embodiment, the splicing terminal assembly  20  is used for the main line aluminium electric cable  10 , and the copper electric cable  15  is branched from the main line aluminium electric cable  10  through the splicing terminal assembly  20 . In particular, if a portion of the aluminium electric cable  10  that is press-contacted with the insulation displacement terminal in the splicing terminal assembly  20  is located under a hard condition in which cooling and heating actions are repeated at a mounting position of a wire harness, the core wire  11  of the aluminium electric cable  10  repeats contraction and expansion. In particular, when the core wire  11  is contracted, a gap is caused between the core wire  11  and the groove edges  34  of the press-contact grooves  33 , thereby involving a possibility that another contact resistance may be generated. 
         [0074]    In view of the above problem, the second embodiment further improves the splicing terminal assembly  20 . As shown in  FIG. 9 , the right and left groove edges  34  of the press-contact grooves  33  of each press-contact blade  32  of the insulation displacement terminal  30  are provided on substantially whole lengths with the stripping tooth section  70 . The stripping tooth section  70  includes a plurality of teeth  71  that have sharply angled crest-like shape with the gentle slopes  72  at the upstream side and the steep slopes  73  at the downstream side, as is the case with the first embodiment. 
         [0075]    According to the above structure, while the exposed core wire  11  in the aluminium electric cable  10  is being pushed down along the groove edges  34  to the regular position in the press-contact grooves  33 , the stripping tooth section  70  continues to slide on the surface of the core wire  11 . In particular, in the upper side area of the press-contact grooves  33 , the stripping tooth section  70  strips the oxide layer on the surface of the core wire  11 . In the lower area including the regular pushing position, the stripping tooth section  70  rather bites the emergent surface of the core wire  11 . 
         [0076]    Accordingly, in the case where the aluminium electric cable  10  is disposed at the finished press-contact position, even if the press-contacted portions of the cable  10  are cooled and contracted, the stripping tooth section  70  bites the surface of the core wire  11 , so that a contact condition between the core wire  11  and the groove edges  34  of the press-contact grooves  33  is maintained, thereby preventing the contact resistance from being generated. 
       Third Embodiment 
       [0077]      FIG. 10  shows a third embodiment of the splicing terminal assembly in accordance with the present invention. Generally, the insulation displacement terminal  30  is formed by cutting and bending a copper or copper alloy plate into a given shape by a press machine. Then, the terminal  30  is dipped in molten tin (Sn) to plate the terminal  30 . 
         [0078]    In the third embodiment, an approximately half area  80  of the right and left groove edges  34  of the press-contact grooves  33  in the press-contact blades  32  near the guide portion  35  is masked before plating. Accordingly, the groove edges  34  on the area  80  are left as originally cut surfaces. In result, stripping portions  81  are provided with relatively rough surfaces. 
         [0079]    According to the third embodiment, when the insulation sheath  13  of the aluminium electric cable  10  is broken by the press-contact grooves  33  in the press-contact blades  32  to expose the core wire  11  and the exposed core wire  11  is pushed down into the grooves  33 , firstly both side stripping portions  81  slide on the surface of the core wire  11 . Specifically, when the rough surfaces of the stripping portions  81  slide on the surface of the core wire  11  in sequence, the oxide layer generated on the surface of the core wire  11  is stripped. 
         [0080]    Secondly, when the aluminium electric cable  10  is pushed down into the regular position in the press-contact grooves  33 , the emergent surface formed by stripping the oxide layer on the surface of the core wire  11  is pushed onto and contacted with the lower side Sn-plated area on both groove edges  34  of the press-contact grooves  33 . At this time, aluminium Al on the emergent surface and plating tin (Sn) are alloyed and the core wire  11  and groove edges  34  in the press-contact grooves  33  are brought into contact with each other. Consequently, the contacting portion between the core wire  11  and the press-contact blades  32  (that is, press-contacted portion of the aluminium electric cable  10 ) will lower the electrical resistance, thereby enhancing an electrical performance. 
       The Other Embodiments 
       [0081]    It should be noted that the present invention is not limited to the above embodiments described above and illustrated in the drawings. For example the following embodiments will fall within a technical scope of the present invention. 
         [0082]    (1) Although the stripping tooth section or the stripping section comprising the original rough cut surfaces is provided on both groove edges of the press-contact groove in the above embodiments, the stripping tooth section or the stripping section may be provided on only either of the groove edges. 
         [0083]    (2) The crest-like shape of each tooth that constitutes the stripping section may be any type shape such as upper and lower sides slopes having the same slant angle, and upper side slant surface and lower side horizontal surface. 
         [0084]    (3) The stripping tooth section may be provided with a plurality of teeth that are juxtaposed and spaced apart from one another by a given distance. 
         [0085]    (4) The insulation displacement terminal may be provided with two front and rear press-contact blades that are shifted in a right and left direction. The insulation displacement terminal may include a single press-contact blade or more than three press-contact blades. 
         [0086]    (5) The insulation displacement terminal may be provided instead of a crimp section (barrel) of a male terminal or a female terminal to be connected to an end of a covered electric cable at a rear side from a connecting section to be connected to a mating terminal. 
         [0087]    (6) The splicing terminal assembly may be provided with two insulation displacement terminals juxtaposed laterally and connected to each other. 
         [0088]    (7) The present invention can be applied to a joint terminal in which a plurality of insulation displacement terminals are juxtaposed laterally and connected to one another. 
         [0089]    (8) Although the aluminium electric cable is exemplified as the covered electric cable to be connected to the insulation displacement terminal in the above embodiments, the other electric cables such as a copper electric cable may be utilized. 
         [0090]    (9) The original cut rough surfaces of the groove edges that are not plated in the third embodiment may be formed on inner longitudinal areas in the groove edges of the press-contact grooves.