Patent Publication Number: US-9837745-B2

Title: Connector terminal with one or more top side contact portions and three linear bottom side contact portions

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a connector terminal, particularly to a connector terminal that, when being fitted with a counter connector terminal, which has a flat plate shape and has top and bottom surfaces, along a fitting axis so that its contact portions corresponding to the top and bottom surfaces of the counter connector terminal come into contact with the top and bottom surfaces, enables the electric connection with the counter connector terminal to be established. 
     In electric wiring using, for instance, a wire harness for vehicles, a connector has heretofore widely been used which establishes the electric connection when a plug terminal in a flat plate shape is inserted into a socket terminal in a box shape so that the plug terminal is sandwiched from top and bottom between a plurality of contact portions of the socket terminal. 
     For instance, JP 2013-98088 A discloses a connector terminal in which a socket terminal  1  has three elongate convex contact portions  2 A to  2 C formed on an inner facing contact surface  2  and one dome-shaped embossed contact  3 A formed on a resilient contact piece  3  and a flat plug terminal  4  is sandwiched between the elongate convex contact portions  2 A to  2 C and the dome-shaped embossed contact  3 A, as shown in  FIG. 11 . 
     As shown in  FIG. 12 , the three elongate convex contact portions  2 A to  2 C of the socket terminal  1  are disposed on the inner facing contact surface  2  so as to be located at three vertices of a triangle, and the dome-shaped embossed contact  3 A is located in a central portion of the triangle formed by the three elongate convex contact portions  2 A to  2 C and at a substantially equal distance from any of the three elongate convex contact portions  2 A to  2 C. 
     When the plug terminal  4  is fitted with the socket terminal  1 , the elongate convex contact portions  2 A to  2 C of the socket terminal  1  come into contact with a top surface  4 A of the plug terminal  4 , while the dome-shaped embossed contact  3 A of the socket terminal  1  comes into contact with a bottom surface  4 B of the plug terminal  4 , whereby the electric connection is established between the socket terminal  1  and the plug terminal  4 . 
     In the connector terminal described in JP 2013-98088 A and shown in  FIGS. 11 and 12 , when the socket terminal  1  and the plug terminal  4  are fitted with each other, the dome-shaped embossed contact  3 A formed on the resilient contact piece  3  of the socket terminal  1  comes into contact with the bottom surface  4 B of the plug terminal  4 , so that the plug terminal  4  is elastically pressed against the inner facing contact surface  2  of the socket terminal  1 , and accordingly, a load is exerted from the top surface  4 A of the plug terminal  4  to each of the three elongate convex contact portions  2 A to  2 C formed on the inner facing contact surface  2  of the socket terminal  1 . 
     When loads acting on the three elongate convex contact portions  2 A to  2 C are unequal, the contact resistance between each of the elongate convex contact portions  2 A to  2 C and the top surface  4 A of the plug terminal  4  varies, which may cause heat to be locally generated. 
     SUMMARY OF THE INVENTION 
     The present invention aims at removing the drawback described above and providing a connector terminal that can reduce the variance in contact resistance among a plurality of contact portions that make contact with a counter connector terminal in a flat plate shape, thereby preventing heat from being locally generated. 
     A connector terminal according to the present invention is one that, when being fitted along a fitting axis with a counter connector terminal in a flat plate shape having a top surface and a bottom surface such that its contact points separately corresponding to the top surface and the bottom surface of the counter connector terminal come into contact with the top surface and the bottom surface, establishes an electric connection with the counter connector terminal, and the connector terminal comprises: 
     one or more top side contact portions each of which makes contact with the top surface of the counter connector terminal; and 
     three bottom side contact portions each of which is linear, extends along the fitting axis, and makes contact with the bottom surface of the counter connector terminal, 
     wherein the three bottom side contact portions are arranged such that centers of the three bottom side contact portions form an isosceles triangle, and 
     wherein the one or more top side contact portions are, when viewed in a direction perpendicular to the top surface of the counter connector terminal in a fitted state, positioned in a straight line that lies between a base of the isosceles triangle and a vertex of the isosceles triangle facing the base and extends parallel to the base in such a manner that a ratio of a distance from the base to a distance from the vertex is 1:2. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a connector terminal according to Embodiment 1 and a counter connector terminal in the non-fitted state. 
         FIG. 2  is a perspective view showing a base member on which bottom side contact portions of the connector terminal according to Embodiment 1 are formed. 
         FIG. 3  is a perspective view showing a housing on which a top side contact portion of the connector terminal according to Embodiment 1 is formed. 
         FIG. 4  is a cutaway perspective view showing the inside of the housing used in the connector terminal according to Embodiment 1. 
         FIG. 5  is a cutaway perspective view showing an upper portion of the housing used in the connector terminal according to Embodiment 1. 
         FIG. 6  is a cutaway plan view showing the arrangement of the top side contact portion and bottom side contact portions of the connector terminal according to Embodiment 1. 
         FIG. 7  is a cutaway side view showing the internal structure of the connector terminal according to Embodiment 1. 
         FIG. 8  is a perspective view showing the connector terminal according to Embodiment 1 and the counter connector terminal in the fitted state. 
         FIG. 9  is a cutaway perspective view showing an upper portion of a connector terminal according to Embodiment 2. 
         FIG. 10  is a cutaway side view showing the internal structure of the connector terminal according to Embodiment 2. 
         FIG. 11  is a cross-sectional view schematically showing a conventional connector terminal in the fitted state. 
         FIG. 12  is a plan view schematically showing the conventional connector terminal. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention are described below based on the appended drawings. 
     Embodiment 1 
     As shown in  FIG. 1 , a connector terminal  11  according to Embodiment 1 of the invention is a socket terminal including a socket portion  12  in a box shape having formed therein a counter connector terminal accommodating portion S, and a counter connector terminal  21  is a plug terminal in a flat plate shape. When the counter connector terminal  21  is inserted into the counter connector terminal accommodating portion S of the socket portion  12  of the connector terminal  11  along a fitting axis C 1 , the connector terminal  11  and the counter connector terminal  21  are fitted with each other, thus establishing the electric connection. 
     The connector terminal  11  includes an electric wire holding portion  13  that is formed at the back end of the socket portion  12  along the fitting axis C 1  to be integral with the socket portion  12 . 
     The socket portion  12  includes a base member  14  integral with the electric wire holding portion  13  and a housing  15  retaining the base member  14  and covering the outer periphery of the base member  14 . The base member  14  and the housing  15  are each made of a conductive material such as a metal. The base member  14  has a flat plate shape. 
     The housing  15  includes a bottom plate portion  16 , a ceiling portion  17  facing the bottom plate portion  16  in parallel therewith, and a pair of lateral wall portions  18  each of which connects either lateral end of the bottom plate portion  16  to the corresponding lateral end of the ceiling portion  17 . The housing  15  is thus in a box shape which is open at the front and back ends in the direction of the fitting axis C 1 . The base member  14  is fixed to a surface of the bottom plate portion  16  of the housing  15  configured as above. 
     At the front end of the socket portion  12  opposite from the end at which the electric wire holding portion  13  is located, the open front end of the housing  15  constitutes an insertion port  19  for receiving the counter connector terminal  21 . 
     For ease of understanding, a plane along which the bottom plate portion  16  and ceiling portion  17  of the housing  15  extend is called “XY plane,” a plane along which the lateral wall portions  18  extend “YZ plane,” a direction in which the fitting axis C 1  extends from the socket portion  12  toward the electric wire holding portion  13  “+Y direction,” and a direction from the bottom plate portion  16  of the housing  15  toward the ceiling portion  17  thereof “+Z direction.” 
     The counter connector terminal  21  is of a flat plate shape having a uniform thickness and extending along an XY plane. The counter connector terminal  21  includes a top surface  21 A extending along the XY plane and facing in the +Z direction and a bottom surface  21 B extending along the XY plane in parallel with the top surface  21 A and facing in the −Z direction. 
     As shown in  FIG. 2 , three bottom side contact portions  14 A to  14 C are formed on a surface of the base member  14  in a flat plate shape. The three bottom side contact portions  14 A to  14 C are linear contact portions projecting from the surface of the base member  14  in the +Z direction and extending along the Y direction, that is, the fitting axis C 1 , and are non-spring contact portions that make contact with the bottom surface  21 B of the counter connector terminal  21  in the fitted state. The bottom side contact portions  14 A to  14 C are arranged to form an isosceles triangle T in an XY plane with the center of the bottom side contact portion  14 A being set as a vertex A and a line segment connecting the centers of the remaining bottom side contact portions  14 B and  14 C being set as a base BC. 
     The base BC of the isosceles triangle T extends in the X direction, and a median AM connecting a midpoint M of the base BC to the vertex A of the isosceles triangle T extends in the Y direction. The isosceles triangle T is symmetrical with respect to a YZ plane passing through the median AM. The median AM of the isosceles triangle T is positioned in the same YZ plane as the YZ plane passing through the fitting axis C 1 , and the three bottom side contact portions  14 A to  14 C are arranged symmetrically with respect to the YZ plane passing through the fitting axis C 1 , i.e., a perpendicular plane that is perpendicular to the top surface  21 A of the counter connector terminal  21  in the fitted state and passes through the fitting axis C 1 . 
     The structure of the housing  15  is shown in  FIG. 3 . A pair of claws  16 A projecting in the +Z direction and being slightly bent toward the +Y direction are formed at the −Y direction-side end of the bottom plate portion  16  of the housing  15 , and a pair of openings  18 A lying adjacent to the bottom plate portion  16  and opening along the Y direction are separately formed in the pair of lateral wall portions  18  of the housing  15 . The pair of claws  16 A and the pair of openings  18 A serve to retain the base member  14  in the housing  15 . The base member  14  is fixed to the inside of the housing  15  as shown in  FIG. 1  with the −Y direction-side end of the base member  14  being caught on the pair of claws  16 A and both lateral edges of the base member  14  being inserted in the pair of openings  18 A. 
     A top side contact portion  15 A that makes contact with the top surface  21 A of the counter connector terminal  21  in the fitted state is formed in the housing  15 . 
       FIG. 4  is a drawing showing the inside of the housing  15  with a +X direction-side half of the ceiling portion  17  of the housing  15  and, of the pair of lateral wall portions  18 , a +X direction-side lateral wall portion  18  being removed, and  FIG. 5  is a drawing showing only a +Z direction-side portion of the housing  15  with a −Z direction-side half of the housing  15  being removed. As shown in  FIG. 4 , a −Y direction-side end of the ceiling portion  17  of the housing  15  is so bent back inwardly as to extend in the +Y direction, thus forming a plate spring  20  with a V-shaped bent portion at its middle section in the Y direction that projects in the −Z direction. The top side contact portion  15 A is formed of the bent portion of the plate spring  20  and, as shown in  FIG. 5 , constitutes a linear spring contact portion extending over the entire width of the plate spring  20  in the X direction and facing in the −Z direction. 
     The plate spring  20  is positioned symmetrically with respect to the YZ plane passing through the fitting axis C 1  and has a symmetrical shape. The top side contact portion  15 A formed of the bent portion of the plate spring  20  is also positioned symmetrically with respect to the YZ plane passing through the fitting axis C 1 , i.e., a perpendicular plane that is perpendicular to the top surface  21 A of the counter connector terminal  21  in the fitted state and passes through the fitting axis C 1 , as well as having a symmetrical shape. 
     As shown in  FIG. 6 , when viewed in the Z direction, that is, a direction perpendicular to the top surface  21 A of the counter connector terminal  21  in the fitted state, the top side contact portion  15 A is positioned on a straight line SL that lies between the vertex A and the base BC of the isosceles triangle T, which is formed with the centers of the three bottom side contact portions  14 A to  14 C, and extends parallel to the base BC in such a manner that the ratio of a distance L 2  from the base BC to a distance L 1  from the vertex A is 1:2. 
       FIG. 7  is a drawing showing the positional relationship between the top side contact portion  15 A of the housing  15  and the bottom side contact portions  14 A to  14 C of the base member  14  fixed in the housing  15  with the +X direction-side half of the ceiling portion  17  of the housing  15  and, of the pair of lateral wall portions  18 , the +X direction-side lateral wall portion  18  being removed similarly to  FIG. 4 . The top side contact portion  15 A and the bottom side contact portions  14 A to  14 C are arranged so that the distance L 1  in the Y direction from the vertex A in the center of the bottom side contact portion  14 A to the top side contact portion  15 A is twice as long as the distance L 2  in the Y direction from the base BC formed with the centers of the bottom side contact portions  14 B and  14 C to the top side contact portion  15 A. 
     Next, the function of the connector terminal  11  in a fitting process is described. As shown in  FIG. 8 , when the counter connector terminal  21  is inserted into the counter connector terminal accommodating portion S through the insertion port  19  of the socket portion  12  of the connector terminal  11 , the plate spring  20  of the housing  15  is pressed by the counter connector terminal  21  and thereby elastically deforms, and the top side contact portion  15 A that is linear and extends in the X direction as shown in  FIG. 5  comes into contact with the top surface  21 A of the counter connector terminal  21 , while the bottom side contact portions  14 A to  14 C that are arranged on the base member  14 , are linear, and extend in the Y direction as shown in  FIG. 2  come into contact with the bottom surface  21 B of the counter connector terminal  21 . 
     At this time, the insertion of the counter connector terminal  21  causes the plate spring  20  to elastically deform, whereby a contact force N 1  is exerted in the −Z direction from the top side contact portion  15 A of the housing  15  to the top surface  21 A of the counter connector terminal  21 . Since the counter connector terminal  21  receives the contact force N 1  from the top side contact portion  15 A, a load acts on each of the three bottom side contact portions  14 A to  14 C through the bottom surface  21 B of the counter connector terminal  21  in the −Z direction. 
     As described above, the top side contact portion  15 A is positioned symmetrically with respect to the YZ plane passing through the fitting axis C 1  and has a symmetrical shape, as well as being positioned on the straight line SL that lies between the vertex A and base BC of the isosceles triangle T, which is formed with the centers of the three bottom side contact portions  14 A to  14 C, and extends parallel to the base BC in such a manner that the ratio of the distance L 2  from the base BC to the distance L 1  from the vertex A is 1:2 when viewed in the Z direction. 
     Accordingly, assuming that the contact force N 1  is exerted from the center of the top side contact portion  15 A extending in the X direction to the top surface  21 A of the counter connector terminal  21  in a concentrated manner, the contact force N 1  acts on a point that internally divides the median AM, which connects the midpoint M of the base BC to the vertex A of the isosceles triangle T, in such a manner that the distance L 1  from the vertex A is twice as long as the distance L 2  from the midpoint M (i.e., L 1 :L 2 =2:1). As a result, a load with a magnitude of N 1 /3 acts on the center of the bottom side contact portion  14 A on the vertex A side of the isosceles triangle T, while loads with a magnitude of 2×N 1 /3 in total act on the centers of the bottom side contact portions  14 B and  14 C at the base BC side, thereby achieving the balance of forces and the balance of moments. In addition, since the bottom side contact portions  14 B and  14 C are arranged symmetrically with respect to the YZ plane passing through the fitting axis C 1 , a load with a magnitude of N 1 /3 acts on each of the centers of the bottom side contact portions  14 B and  14 C. 
     Thus, loads are equally exerted from the bottom surface  21 B of the counter connector terminal  21  to the three bottom side contact portions  14 A to  14 C, which can reduce the variance in contact resistance among the bottom side contact portions  14 A to  14 C that make contact with the bottom surface  21 B of the counter connector terminal  21  in a flat plate shape, thereby preventing heat from being locally generated. 
     In contrast, in the conventional connector terminal shown in  FIG. 12 , although the centers of the three elongate convex contact portions  2 A to  2 C are arranged to form an isosceles triangle, a distance L 3  from the center of the elongate convex contact portion  2 A at a vertex D of the isosceles triangle to the center G of the dome-shaped embossed contact  3 A is substantially equal to a distance L 4  from a midpoint H between the centers of the elongate convex contact portions  2 B and  2 C at both ends of the base EF of the isosceles triangle to the center G of the dome-shaped embossed contact  3 A. Therefore, when a contact force N 2  is exerted from the center G of the dome-shaped embossed contact  3 A to the plug terminal, a load with a magnitude of N 2 /2 acts on the center of the elongate convex contact portion  2 A at the vertex D, while a load with a magnitude of N 2 /4 acts on each of the centers of the elongate convex contact portions  2 B and  2 C at both ends of the base EF. Thus, loads unequally act on the three elongate convex contact portions  2 A to  2 C, whereby the contact resistance of each of the elongate convex contact portions  2 A to  2 C varies, which may cause heat to be locally generated. 
     Embodiment 2 
     While in Embodiment 1 above, the housing  15  has the top side contact portion  15 A extending over the entire width of the plate spring  20  in the X direction, the invention is not limited thereto. For example, as in a connector terminal  31  shown in  FIGS. 9 and 10 , a pair of top side contact portions  35 A may be disposed at the same distance in the +X and −X directions from the YZ plane passing through the fitting axis C 1 . Those top side contact portions  35 A are arranged symmetrically with respect to the YZ plane passing through the fitting axis C 1  and have a symmetrical shape. 
     The connector terminal  31  includes a socket portion  32  and an electric wire holding portion  33  integral with the socket portion  32 . The socket portion  32  includes a bottom plate portion  34 , a ceiling portion  35  facing the bottom plate portion  34  in parallel therewith, and a pair of lateral wall portions  36  each of which connects either lateral end of the bottom plate portion  34  to the corresponding lateral end of the ceiling portion  35 . 
     The ceiling portion  35  is divided at its center portion along the fitting axis C 1  into two upper plate portions  37 , and a pair of spring portions  38  having a cantilever shape are formed which is bent at the −Y direction-side end of the upper plate portions  37  toward the inside of the socket portion  32  and extend in the +Y direction. The top side contact portions  35 A are separately disposed at the tip ends of the spring portions  38 . The pair of spring portions  38  are the same in size and spring constant. 
     Three bottom side contact portions  34 A to  34 C are formed on the bottom plate portion  34  of the socket member  32 . As with the bottom side contact portions  14 A to  14 C in Embodiment 1, the bottom side contact portions  34 A to  34 C are linear and non-spring contact portions projecting from a surface of the bottom plate portion  34  in the +Z direction and extending along the Y direction, that is, the fitting axis C 1 , and are arranged to form an isosceles triangle in an XY plane with the center of the bottom side contact portion  34 A being set as a vertex A and a line segment connecting the centers of the remaining bottom side contact portions  34 B and  34 C being set as a base BC. 
     The pair of top side contact portions  35 A are, when viewed in the Z direction, positioned on a straight line that lies between the vertex A and base BC of the isosceles triangle, which is formed with the centers of the three bottom side contact portions  34 A to  34 C, and extends parallel to the base BC in such a manner that the ratio of a distance L 2  from the base BC to a distance L 1  from the vertex A is 1:2. 
     While in Embodiment 1 above, the housing  15  having the top side contact portion  15 A and the base member  14  having the three bottom side contact portions  14 A to  14 C are separate components, in the connector terminal  31  of Embodiment 2 shown in  FIGS. 9 and 10 , the pair of top side contact portions  35 A and the three bottom side contact portions  34 A to  34 C are disposed at the socket portion  32  formed as a single component. 
     In a fitting process, the insertion of the counter connector terminal  21  causes the pair of spring portions  38  to elastically deform, whereby contact forces of the same magnitude are exerted in the −Z direction from both top side contact portions  35 A to the top surface  21 A of the counter connector terminal  21 , and the resultant force of the two contact forces acts on the middle position between the pair of top side contact portions  35 A, i.e., near the fitting axis C 1  in the X direction. Therefore, loads are equally exerted to the three bottom side contact portions  34 A to  34 C, which can reduce the variance in contact resistance, thereby preventing heat from being locally generated. 
     In addition, since the pair of top side contact portions  35 A are disposed at the same distance in the +X and −X directions from the YZ plane passing through the fitting axis C 1 , when a moment in the XY plane acts on the counter connector terminal  21  fitted with the connector terminal  31 , a frictional force is exerted from each of the pair of top side contact portions  35 A, which is effective at minimizing displacement of the counter connector terminal  21  in a rotational direction in the XY plane. 
     Also when a moment about the fitting axis C 1  acts on the counter connector terminal  21  fitted with the connector terminal  31 , in addition to contact forces exerted from the pair of top side contact portions  35 A to the counter connector terminal  21  upon fitting of the counter connector terminal  21 , a normal force having a magnitude corresponding to the moment is generated from one of the top side contact portions  35 A to the counter connector terminal  21 , so that the displacement of the counter connector terminal  21  in a rotational direction in the XZ plane can be minimized. 
     With a longer distance between the YZ plane passing through the fitting axis C 1  and each of the top side contact portions  35 A, the configuration more effectively works against a moment exerted to the counter connector terminal  21 , thereby minimizing displacement of the counter connector terminal  21  in a rotational direction. 
     It should be noted that three or more top side contact portions may be provided as long as they are, when viewed in the Z direction, positioned on the straight line that lies between the vertex A and base BC of the isosceles triangle, which is formed with the centers of the three bottom side contact portions  34 A to  34 C, and extends parallel to the base BC in such a manner that the ratio of the distance L 2  from the base BC to the distance L 1  from the vertex A is 1:2. Even when, for instance, an external force acts due to vibration or other factors, the provision of two or more top side contact portions serves to minimize displacement of the counter connector terminal  21  relative to the connector terminal  11  whereby the top and bottom side contact portions are prevented from being worn away. 
     In addition, even with merely a single top side contact portion which is positioned on the straight line that lies between the vertex A and base BC of the isosceles triangle to be parallel to the base BC in such a manner that the ratio of the distance L 2  from the base BC to the distance L 1  from the vertex A is 1:2 and also positioned in the YZ plane passing through the fitting axis C 1 , it is possible to reduce the variance in contact resistance by equalizing loads exerted to the three bottom side contact portions  34 A to  34 C, thereby preventing heat from being locally generated. 
     For Embodiment 1 above, the configuration may also be employed in which the base member  14  and the housing  15  are integral with each other and the top side contact portion  15 A and the three bottom side contact portions  14 A to  14 C are disposed at the socket portion  12  which is a single component. 
     Aside from that, while the three bottom side contact portions  14 A to  14 C in Embodiment 1 and the three bottom side contact portions  34 A to  34 C in Embodiment 2 are constituted of non-spring contact portions, the contact portions  14 A to  14 C and  34 A to  34 C may be spring contact portions as with the top side contact portions  15 A and  35 A.