Patent Publication Number: US-10770817-B2

Title: Terminal module

Description:
BACKGROUND 
     Field of the Invention 
     This specification relates to a terminal module. 
     Related Art 
     Japanese Unexamined Patent Publication No. 2008-204634 discloses a contact device for connecting a pair of terminals using a conductive coil spring between the terminals. The coil spring of Japanese Unexamined Patent Publication No. 2008-204634 is formed into a spring contact having an elliptical winding surface by inclining a wire made of a conductive spring material with respect to a winding axis and spirally winding the wire. Further, both end parts of the wire of the spring contact are joined into an annular shape, and the annular spring contact is fit in grooves in the outer peripheries of the terminals. 
     However, if the spring contact is used in an annular state, grooves are formed in cylindrical outer surfaces or cylindrical inner outer surfaces. Forming grooves increases cost. Further, since the spring contact is used in the annular state, miniaturization is difficult. Furthermore, if the spring contact is used in a straight state, the entire length of the spring contact becomes shorter when the wire is tilted and deformed. However, if the spring contact is used in the annular state, the entire length is maintained. Therefore, tensile stress acts on the wire and the wire easily is settled. Thus, the spring contact desirably is used in the straight state without being formed into an annular shape. However, if the straight spring contact is brought into contact with a surface of a busbar, it is difficult to ensure a contact pressure if the surface of the busbar is a smooth surface since the wire of the spring contact slides on the surface of the busbar. As a result, even if the wire having the same thickness is used, it is difficult to reduce contact resistance as compared to the case where the spring contact is used in the annular state. 
     SUMMARY 
     A terminal module disclosed by this specification includes an electrical contact member having a body configured to face a butting portion on a mating terminal, and an obliquely wound coil spring coiled by winding a conductive wire material a plurality of times. The coil spring is oriented such that a coil axis is parallel to the body of the electrical contact, and is configured to be sandwiched between the mating terminal and the electrical contact member to be tilted toward the coil axis when the mating terminal and the electrical contact member approach. At least one of a facing surface on the body of the electrical contact on which the obliquely wound coil spring slides and a contact surface on the butting portion of the mating terminal on which the obliquely wound coil spring slides is formed into an uneven surface for increasing frictional resistance during sliding. 
     According to this configuration, at least one of the contact surface and the facing surface is formed into an uneven surface, frictional resistance increases by the obliquely wound coil spring sliding on the uneven surface. Thus, the obliquely wound coil spring is less likely to be tilted toward the coil axis and a contact pressure increases, with the result that contact resistance is reduced. The conductive wire material of the obliquely wound coil spring may be thickened to increase the contact pressure, but this design is not a good idea for the following reasons. If the conductive wire material is thickened, the obliquely wound coil spring becomes larger. This is disadvantageous in miniaturizing the entire terminal module. In addition, the flexibility of the conductive wire material is reduced to make the obliquely wound coil spring easily settled. 
     In short, by adopting the above configuration, connection reliability equal to or more than that before can be obtained while the conductive wire material thinner than before is used. Further, by thinning the conductive wire material, flexibility increases, the settling of the obliquely wound coil spring is less likely to occur and the entire terminal module can be miniaturized. Further, since the obliquely wound coil spring need not be formed into an annular shape, the terminal module can be processed inexpensively. Furthermore, the obliquely wound coil spring is enabled to be naturally deflected and deformed. Therefore extra stress and the like do not act on the conductive wire material and an effect of making the obliquely wound coil spring less likely to be settled can be expected. 
     Both the facing surface and the contact surface may be formed into uneven surfaces. According to this configuration, the obliquely wound coil spring is less likely to be tilted with respect to the coil axis. Thus, the contact pressure increases and the contact resistance decreases. As a result larger current applications can be dealt with. 
     A holder may hold the electrical contact member and the obliquely wound coil spring, and the mating terminal may be insertable into the holder. According to this configuration, the configuration of the electrical contact member can be simplified as compared to the case where the obliquely wound coil spring is held by the electrical contact member. For example, the electrical contact member need not be provided with a hole or the like for fixing the obliquely wound coil spring. Thus, the processing cost of the electrical contact member is reduced and a conductor cross-sectional area of the electrical contact member is not reduced by the hole. 
     According to the terminal module disclosed by this specification, the obliquely wound coil spring is less likely to be tilted toward the coil axis and the contact pressure can be increased. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view of a terminal module. 
         FIG. 2  is a plan view of the terminal module. 
         FIG. 3  is an exploded perspective view of the terminal module. 
         FIG. 4  is a back view showing a state before the terminal module is connected to a mating terminal. 
         FIG. 5  is a section along A-A in  FIG. 4 . 
         FIG. 6  is a back view showing a state after the terminal module is connected to the mating terminal. 
         FIG. 7  is a section along B-B in  FIG. 6 . 
         FIG. 8  is a perspective view showing a state where an obliquely wound coil spring is disposed between a contact surface and a facing surface. 
         FIG. 9  is a perspective view showing a state where an obliquely wound coil spring is disposed between a contact surface and a facing surface in another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment is described with reference to  FIGS. 1 to 8 . A terminal module  10  of this embodiment is connected electrically to a mating terminal  80  by being butted against the mating terminal  80 . The terminal module  10  includes an electrical contact  20 , a holder  40  and an obliquely wound coil spring  60 . In the following description, an upper side in  FIG. 4  is referred to as an upper side and a lower side in  FIG. 4  (side of the mating terminal  80 ) is referred to as a lower side. Further, a left side in  FIG. 1  is referred to as a front side and a right side in  FIG. 1  (side of an externally connecting portion  21 ) is referred to as a rear side. 
     As shown in  FIGS. 1 and 3 , the electrical contact  20  is formed by press-working a metal plate material, such as copper alloy, and is substantially L-shaped. The electrical contact  20  has a facing surface  31  to be brought into contact with the obliquely wound coil spring  60 , and includes a body  30  configured to face a butting portion  82  of the mating terminal  80  and the externally connecting portion  21  rising up while being perpendicular to the body  30  and to be connected to an external circuit. The externally connecting portion  21  is provided with an elongated bolt hole  23 . As shown in  FIG. 8 , the facing surface  31  is formed into a twill knurled uneven surface. Such knurling is performed, for example, by press-working. 
     As shown in  FIGS. 3 and 5 , the body  30  is a flat plate and has a rectangular plan view shape with longer sides extending in a front-rear direction and shorter sides extending in a width direction. A dimension of the body portion  30  in the width direction is larger than that of the obliquely wound coil spring  60  in the width direction, and the body portion  30  is formed to have an equal width in the front-rear direction. The lower surface of the body  30  serves as the facing surface  31  described above. A locking hole  33  to be locked to a locking projection  53 A of a locking lance  53  to be described later is provided in a front part of the body  30 . The locking hole  33  is provided at a position near one widthwise end of the body  30 , and a through hole having a rectangular shape in a plan view. Further, a retaining portion  35  is provided on a rear part of the body  30 . The retaining portion  35  is formed by being cut and is deformed down at a widthwise central position. The lower end position of the retaining portion  35  is lower than a position where a holding shaft  55  to be described later is provided. A dimension of the body  30  in the front-rear direction is longer than a dimension of the obliquely wound coil spring  60  in an axial direction (front-rear direction), and the locking hole  33  and the retaining portion  35  are provided before and after a position to be brought into contact with the obliquely wound coil spring  60 . 
     The holder  40  is made of synthetic resin and, as shown in  FIGS. 3 and 5 , formed into a box shape as a whole by a front wall  41 , a locking portion  43  provided behind and adjacent to the front wall  41  and two holding walls  45  extending rearward from a rear end surface  43 A of the locking portion  43 . A front end part of the body  30  of the electrical contact  20  is in contact with the rear surface of the front wall  41 . The holding walls  45  extending in parallel are disposed at a predetermined interval from each other, and a lower opening open downward of a space between the holding walls  45  serves as an opening  47  into which the mating terminal  80  is inserted. An inner dimension between the holding walls  45  (width of the opening  47 ) is equal to or slightly larger than an outer dimension of the mating terminal  80  in the width direction. 
     Further, as shown in  FIGS. 3 and 5 , holding grooves  51  are provided in upper end parts of the holding walls  45  and are capable of holding the body  30  of the electrical contact  20  inserted therein. The holding groove  51  is provided by recessing the inner surface of the holding wall  45  outwardly in the width direction. Groove widths of the holding grooves  51  are equal to or slightly larger than a plate thickness of the body  30  of the electrical contact  20 . Further, upper wall parts of the holding grooves  51  project farther in than the inner surfaces of the holding walls  45  to suppress upward lifting of the electrical contact member  20 . 
     As shown in  FIG. 3 , the locking portion  43  includes the locking lance  53  extending in a short side direction of the body  30  of the electrical contact  20 . The locking lance  53  is cantilevered from one end toward the other end of the locking portion  43  in the width direction and is resiliently deformable in a vertical direction. Further, a deflection space is provided below the locking lance  53  of the locking portion  43 . Since the locking lance  53  extends in the width direction in this way, a dimension of the locking lance  53  in the front-rear direction can be reduced. Further, the upper surface of the locking lance  53  is substantially flush with lower inner wall parts of the holding grooves  51  and can horizontally hold the body  30  of the electrical contact  20 . Further, a locking projection  53 A lockable to the locking hole  33   o  projects up on the other end side (free end side) of the locking lance  53 . The locking projection  53 A of the locking lance  53  is fit into the locking hole  33  so that the body  30  of the electrical contact member  20  is locked in the holder  40 . 
     As shown in  FIG. 5 , the rear end surface  43 A of the locking portion  43  is parallel to the retaining portion  35  of the electrical contact  20  locked in the holder  40  and located on a side opposite to the retaining portion  35  across the obliquely wound coil spring  60 . As shown in  FIGS. 3 and 5 , the cylindrical holding shaft  55  projects rearward from the rear end surface  43 A of the locking portion  43 . The holding shaft  55  is inserted into the obliquely wound coil spring  60  and holds the obliquely wound coil spring  60  at a position between the facing surface  31  of the electrical contact  20  and a contact surface  81  of the mating terminal  80  to be described later. The rear end of the holding shaft  55  is located at the same position as those of the holding walls  45 , and such a clearance that the obliquely wound coil spring  60  does not fall therethrough is defined between the retaining portion  35  and the holding shaft  55 . 
     As shown in  FIGS. 3 to 5 , the obliquely wound coil spring  60  is formed by spirally winding a conductive wire material  61  with respect to a coil axis P, and is straight along the coil axis P. The inclination of the conductive wire material  61  of the obliquely wound coil spring  60  with respect to the coil axis P is set within 90° (tilted in one direction) when viewed laterally. Further, similarly to general coil springs, an angle to the coil axis P differs at each half turn position, but all of the turns are inclined in the same direction with respect to the coil axis P. An end surface (surface viewed from front or behind) of the obliquely wound coil spring  60  is somewhat elliptical. If a load is applied to sandwich the obliquely wound coil spring  60  from both sides in a minor axis direction, each turn of the conductive wire material  61  is tilted farther toward the coil axis P and is deformed to reduce a height (dimension in a direction perpendicular to the coil axis P) of the obliquely wound coil spring  60 . Note that the obliquely wound coil spring  60  has a nonlinear region where a spring load hardly changes even if a displacement amount of the obliquely wound coil spring  60  (spring height displacement amount) is changed. 
     As shown in  FIGS. 3 and 5 , the obliquely wound coil spring  60  is arranged in such an orientation that the coil axis P thereof is parallel to and along the facing surface  31 . The holding shaft  55  is inserted into the obliquely wound coil spring  60  so that the minor axis direction viewed from the axial direction of the coil axis P is the vertical direction, one end of this holding shaft  55  is coupled to the rear end surface  43 A of the locking portion  43 , and the retaining portion  35  is disposed on the other end. Thus, the obliquely wound coil spring  60  is held so not to come off the holding shaft  55 . 
     A dimension of the obliquely wound coil spring  60  in the front-rear direction in a natural state is shorter than that of the holding shaft  55  in the front-rear direction. Further, the obliquely wound coil spring  60  is tilted toward the coil axis P (to reduce the angle with respect to the coil axis P) by being vertically sandwiched at the time of connection to the mating terminal  80 . Thus, a dimension in the minor axis direction viewed from the axial direction of the coil axis P is reduced and the dimension in the front-rear direction also is reduced due to a narrowed pitch in the front-rear direction 
     The mating terminal  80  is made of conductive metal and is formed into a substantially L shape by bending a flat conductive metal plate extending straight substantially at a right angle, as shown in  FIGS. 4 and 5 . The upper surface of the butting portion  82  of the mating terminal  80  facing the facing surface  31  of the electrical contact  20  serves as the contact surface  81 . A dimension of the butting portion  82  in the front-rear direction is equal to that of the holding shaft  55  in the front-rear direction and is longer than the dimension of the obliquely wound coil spring  60  in the front-rear direction in the natural state. Further, a dimension of the butting portion  82  in the width direction is larger than an outer diameter of the obliquely wound coil spring  60 . As shown in  FIG. 8 , the contact surface  81  of the butting portion  82  is formed into a twill knurled uneven surface. Such knurling is performed, for example, by press-working. 
     The terminal module  10  is configured as described above and an assembling method thereof is described. First, the obliquely wound coil spring  60  is inserted into a rear opening between the holding walls  45  of the holder  40 . When the holding shaft  55  is inserted into the obliquely wound coil spring  60  and the obliquely wound coil spring  60  is pushed forward, an end part of the obliquely wound coil spring  60  contacts the rear end surface  43 A of the locking portion  43  to stop any further forward pushing of the obliquely wound coil spring  60 . 
     With the holding shaft  55  inserted in the obliquely wound coil spring  60 , the electrical contact member  20  is inserted into the holding grooves  51  from behind. When the front end of the body  30  is inserted into the holding grooves  51 , the body  30  is pushed forward and the front end of the body  30  reaches the locking portion  43 , the locking lance  53  is deformed resiliently down. When the locking hole  33  is at a position above the locking projection  53 A, the locking lance  53  resiliently returns, the locking projection  53 A of the locking lance  53  is locked into the locking hole  33  and the electrical contact member  20  is locked in the holder  40 . At this time, since the retaining portion  35  is located on the side opposite to the rear end surface  43 A of the locking portion  43  across the obliquely wound coil spring  60  and almost no clearance is formed between the retaining portion  35  and the rear end of the holding shaft portion  55 , a state where the holding shaft  55  is inserted in the obliquely wound coil spring  60  is held. Further, the upper surface of the locking lance  53  is covered by the electrical contact  20 . Thus, the locking lance  53  is not exposed to outside and unintended unlocking can be suppressed. 
     By inserting the holding shaft  55  in the holder  40  into the obliquely wound coil spring  60 , thereafter inserting the electrical contact  20  into the holder  40  and fitting and locking the locking projection  53 A of the locking lance  53  into the locking hole  33  of the electrical contact member  20  in this way, the electrical contact  20  is locked in the holder  40 . When the electrical contact  20  is locked, the obliquely wound coil spring  60  is positioned by the rear end surface  43 A of the locking portion  43  and the retaining portion  35  and retained with respect to the holding shaft  55 . The terminal module  10  is assembled merely by an assembling operation without using welding or the like, as just described. Thus, the terminal module  10  is manufactured easily. Further, each component can be exchanged even if a trouble caused by aged deterioration during use occurs. Thus, cost for a repair can be reduced. Additionally, the simple structure of mounting the straight obliquely wound coil spring  60  on the outer periphery of the holding shaft  55  is conducive to miniaturization of the terminal module  1 . Further, since it is not necessary to cut a groove or the like for holding the obliquely wound coil spring  60 , processing cost can be reduced. 
     In the assembled terminal module  10 , the inner peripheral surface of the obliquely wound coil spring  60  is supported in contact with the outer peripheral surface of the holding shaft  55 , as shown in  FIGS. 4 and 5  in a state before the mating terminal  80  contacts the obliquely wound coil spring  60 . Since the holding shaft portion  55  is substantially parallel to the facing surface  31  of the electrical contact member  20 , the coil axis P of the obliquely wound coil spring  60  also is substantially parallel to the facing surface  31  of the electrical contact  20 . 
     Subsequently, as the terminal module  10  and the mating terminal  80  are brought closer, the contact surface  81  of the mating terminal  80  contacts a lower end part (lower end part in the minor axis direction) of the outer periphery of the obliquely wound coil spring  60 , and an upper end part (upper end part in the minor axis direction) of the outer periphery of the obliquely wound coil spring  60  contacts the facing surface  31  of the electrical contact  20 . As the obliquely wound coil spring  60  is sandwiched between the contact surface  81  and the facing surface  31 , the conductive wire material  61  is deflected and deformed to be tilted toward the coil axis P while sliding on the contact surface  81  and the facing surface  31 . 
     At this time, the contact surface  81  and the facing surface  31  are formed into twill knurled uneven surfaces, as shown in  FIG. 8  in this embodiment. Thus, frictional resistance between the conductive wire material  61  and the contact surface  81  and between the conductive wire material  61  and the facing surface  31  increases as compared to the case where the contact surface  81  and the facing surface  31  are not formed into uneven surfaces. Since the conductive wire material  61  needs to slide against this frictional resistance, a stronger force is necessary to slide as compared to the case where the contact surface  81  and the facing surface  31  are not formed into uneven surfaces. Specifically, since a stronger force is necessary in both a direction along the contact surface  81  and a direction along the facing surface  31  (i.e. front-rear direction), a stronger force is necessary in both a direction perpendicular to the facing surface  81  and a direction perpendicular to the facing surface  31  (i.e. vertical direction) by that much. As a result, a large contact pressure is generated in the vertical direction between the contact surface  81  and the conductive wire material  61  and between the facing surface  31  and the conductive wire material  61 . Thus, contact resistance can be reduced. 
     Thereafter, as shown in  FIGS. 6 and 7 , the obliquely wound coil spring  60  is sandwiched in the vertical direction between the contact surface  81  of the mating terminal  80  and the facing surface  31  of the electrical contact member  20 . In this way, the mating terminal  80  and the electrical contact  20  are connected electrically via the obliquely wound coil spring  60 . In this state, the electrical contact  20  and the mating terminal  80  are in contact with the obliquely wound coil spring  60  at many points. The many contact points can be ensured and the contact resistance can be reduced. Further end parts of the obliquely wound coil spring  60  are not fixed. Thus, the dimension of the obliquely wound coil spring  60  in the front-rear direction becomes shorter than that before connection to the mating terminal  80  and the settling of the obliquely wound coil spring  60  due to plastic deformation or the like is less likely to occur by the obliquely wound coil spring  60  being deflected and deformed in a state close to a natural state. 
     As described above, at least one of the facing surface  31  and the contact surface  82  is formed into an uneven surface in this embodiment, and the obliquely wound coil spring  60  slides on the uneven surface to increase the frictional resistance. Therefore, the obliquely wound coil spring  60  is less likely to be tilted toward the coil axis P and the contact pressure increases. Accordingly, the contact resistance easily is reduced. The conductive wire material  61  of the obliquely wound coil spring  60  may be thickened only to increase the contact pressure, but this cannot be said to be a good idea for the following reasons. If the conductive wire material  61  is thickened, the obliquely wound coil spring  60  becomes larger. This is disadvantageous in miniaturizing the entire terminal module  10 . In addition, the flexibility of the conductive wire material  61  is reduced to make the obliquely wound coil spring  60  easily settled. 
     In short, by adopting the above configuration, connection reliability equal to or more than that before can be obtained while the conductive wire material  61  thinner than before is used. Further, by thinning the conductive wire material  61 , flexibility increases, the settling of the obliquely wound coil spring  60  is less likely to occur and the entire terminal module  10  can be miniaturized. Further, since the obliquely wound coil spring  60  need not be formed into an annular shape, the terminal module  10  can be processed inexpensively. Furthermore, the obliquely wound coil spring  60  can be deflected and deformed naturally. Therefore extra stress and the like do not act on the conductive wire material  61  and an effect of making the obliquely wound coil spring less likely to be settled can be expected. 
     Both the facing surface  31  and the contact surface  81  may be formed into uneven surfaces. According to this configuration, the obliquely wound coil spring  60  is less likely to be tilted with respect to the coil axis P. Thus, the contact pressure increases and the contact resistance decreases so that larger current applications can be dealt with. 
     The holder  40  holds the electrical contact  20  and the obliquely wound coil spring  60  and into which the mating terminal  80  is insertable. Accordingly, the configuration of the electrical contact  20  can be simplified as compared to the case where the obliquely wound coil spring  60  is held by the electrical contact  20 . For example, since the electrical contact member  20  need not be provided with a hole or the like for fixing the obliquely wound coil spring  60 , the processing cost of the electrical contact  20  is reduced and a conductor cross-sectional area of the electrical contact  20  is not reduced by the hole or the like. 
     The invention is not limited to the above described and illustrated embodiment. For example, the following various modes are also included. 
     Although the facing surface  31  and the contact surface  81  are both formed into uneven surfaces in the above embodiment, only the contact surface  81  may be formed into an uneven surface, as shown in  FIG. 9 . 
     Although the obliquely wound coil spring  60  is held by the holder  40  made of synthetic resin in the above embodiment, the obliquely wound coil spring  60  may be held by assembling a resin component capable of accommodating the obliquely wound coil spring  60  with the body  30 . In this case, a housing made of resin for holding the electrical contact member  20  may be prepared separately and formed with an opening through which the mating terminal  80  is inserted. 
     Although the twill knurled surface is illustrated as an example of the uneven surface in the above embodiment, serration other than a twill pattern may be provided or roughening may be performed by matting. 
     LIST OF REFERENCE SIGNS 
     
         
           10  . . . terminal module 
           20  . . . electrical contact member 
           30  . . . body portion 
           31  . . . facing surface 
           40  . . . holder 
           60  . . . obliquely wound coil spring 
           61  . . . conductive wire material 
           80  . . . mating terminal 
           81  . . . contact surface 
           82  . . . butting portion 
         P . . . coil axis