Patent Publication Number: US-6341978-B1

Title: Press-connecting terminal

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a press-connecting terminal used in the wiring installed in a vehicle such as an automobile. More particularly, the present invention relates to press-connecting blades of the press-connecting terminal which can be electrically connected to an electric wire, connected to the press-connecting terminal, with a small electrical resistance. 
     The present application is based on Japanese Patent Application No. Hei. 11-322956, which is incorporated herein by reference. 
     2. Description of the Related Art 
     In automobiles having various electronic equipments mounted thereon, press-connecting terminals have been extensively used for connecting the electronic equipments together and for connecting wire harnesses together. 
     As shown in FIG. 6, a conventional press-connecting terminal  30  includes a connection portion  31  for connection to a mating male terminal (not shown), a press-connection portion  32  for being press-connected to an end portion of an electric wire  21 , and retaining piece portions  33  for press-holding the electric wire  2 . A resilient contact piece portion  35  for contact with the mating male terminal, inserted into the connection portion  31  through an insertion port  31   a  in a front end thereof, is provided within the connection portion  31 . A lance  36  for retaining the press-connecting terminal, inserted in a connector housing (not shown), against withdrawal, is formed on an upper surface of the connection portion  31 , and also a stabilizer  37  for limiting the inserting direction is formed on the upper surface of the connection portion  31 . 
     The press-connecting portion  32  includes two press-connecting blades  41  and  42 . 
     As shown in FIG. 9, the front press-connecting blade  41  is defined or formed by a pair of opposed projecting pieces  44  which are stamped respectively from opposed (right and left) side plates  39  of the press-connecting portion  32 , and then are bent inwardly. A press-connecting groove  45  is formed between the opposed projecting pieces  44 . The width of this press-connecting groove  45  is smaller than the diameter of a conductor  23  of the electric wire  21 . 
     As shown in FIG. 7, the rear press-connecting blade  42  is formed by stamping a relevant portion of a bottom wall  47  and then by bending it upwardly. This rear press-connecting blade  42  is spaced a predetermined distance from the front press-connecting blade  41 . As shown in FIG. 10, a press-connecting groove  49  is also formed in the press-connecting blade  42 , and the width of this press-connecting groove is equal to the width of the press-connecting groove  45 . 
     Next, the process of press-connecting the electric wire  21  will be described. 
     An end portion of the electric wire  21  is press-fitted into the press-connecting blades  41  and  42  from the upper side of the press-connecting portion  32  as indicated by arrow A in FIG.  6 . As a result, opposed side edges of each of the press-connecting grooves  45  and  49  cut a sheath  22  of the electric wire  21  to contact the conductor  23 , as shown in FIGS. 9 and 10. 
     Then, the electric wire  21  is fastened by the pair of retaining piece portions (barrel portion)  33  through the sheath  22  as shown in FIG. 8, thus completing the fixing of the electric wire  21  to the press-connecting terminal  30 . 
     In the above conventional press-connecting terminal  30 , however, the press-connecting portion  32  is mainly designed to merely firmly press-connect and hold the conductor  23 , and the area of contact of each press-connecting blade  41 ,  42  with the conductor  23  has often been inadequate. 
     Because of this inadequate contact area, an electrical resistance, developing between the conductor  23  and each press-connecting blade  41 ,  42 , increases to generate heat, so that those members around the press-connecting portion are subjected to deterioration, improper contact and so on, and this has resulted in a problem that the safety of the vehicle is affected. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to overcome the above problems of the conventional construction, and an object of the present invention is to provide a press-connecting terminal provided with press-connecting blades which can be electrically connected to an electric wire with a small electrical resistance. 
     To achieve the above object, according to the present invention, there is provided a press-connecting terminal which includes: 
     a base; 
     a connection portion, to which a connection terminal of a mating connector is electrically connectable, disposed on the base; and 
     a press-connecting portion, to which a conductor of an electric wire is electrically connectable, disposed on the base, the press-connecting portion including plural pairs of press-connecting blades, each pair of which have: 
     a pair of bladed, tapering guide surfaces which slant inwardly downwardly, and 
     a pair of opposed inner surfaces, between which a gap smaller than a diameter of the conductor of the electric wire is formed, and which downwardly extend respectively from the pair of tapering guide surfaces; 
     wherein when an electric wire is press-fitted into the gap, the conductor of the electric wire is electrically connected to and held by the plural pairs of press-connecting blades, and 
     wherein an effective total contact area of the opposed inner surfaces of the press-connecting blades with the conductor is set to a value equal to or greater than a cross-sectional area of the conductor. 
     In the press-connecting terminal of the above construction, the functions of the press-connecting blades to press-contact and hold the conductor, as well as the electrical connection of the press-connecting blades to the conductor, can be suitably achieved. Accordingly, those members around the press-connecting portion are prevented from being subjected to deterioration, improper contact and so on by heat produced by the electrical resistance developing between the conductor and each press-connecting blade, and therefore the safety of the vehicle is positively prevented from being affected. 
     In the press-connecting terminal of the above construction, the effective total contact area is such a total of areas that the conductor of the electric wire contacts with the opposed inner surfaces of the press-connecting blades. 
     Therefore, a necessary width of each of the opposed inner surfaces of the press-connecting blades, a necessary size of the gap, and the necessary number of the press-connecting blades may be determined on the basis of the cross-sectional area of the conductor of the electric wire. 
     In other words, the effective total contact area may be set on the basis of at least one of the width of each of the opposed inner surfaces, the size of the gap, and the number of the opposed inner surfaces, with respect to the conductor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing an important portion of a press-connecting terminal of the present invention; 
     FIG. 2 is a view similar to FIG. 1, but showing an electric wire press-fitted in the press-connecting terminal; 
     FIG. 3 is a plan view of the press-connecting terminal of FIG. 2; 
     FIG. 4 is a cross-sectional view taken along the line IV—IV of FIG. 3; 
     FIG. 5 is a perspective view of a press-connecting blade in FIG. 4; 
     FIG. 6 is a perspective view showing an important portion of a conventional press-connecting terminal; 
     FIG. 7 is a plan view of the terminal of FIG. 6; 
     FIG. 8 is a perspective view, showing a condition in which an electric wire is press-fitted in the press-connecting terminal of FIG. 6; 
     FIG. 9 is a cross-sectional view taken along the line IX—IX of FIG. 8; and 
     FIG. 10 is a cross-sectional view taken along the line X—X of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     One preferred embodiment of a press-connecting terminal of the present invention will now be described in detail with reference to FIGS. 1 to  5 . 
     As shown in FIGS. 1 to  3 , the press-connecting terminal  1  of this embodiment is formed by bending an electrically-conductive sheet  2 . This press-connecting terminal  1  broadly includes a connection portion  3  and a press-connecting portion  4 , both of which are disposed on the base of the press-connecting terminal  1 . A male terminal (not shown) in a mating connector can be electrically connected to the connection portion  3 , and an insertion port  5  for receiving the mating male terminal is formed in a front end of the connection portion  3 . A resilient contact piece portion  6  for resiliently contacting with the male terminal in the mating connector is provided within an internal space of the connection portion  3  communicating with the insertion port  5 . 
     The press-connecting portion  4  includes a barrel portion  8 , having a pair of retaining piece portions  8   a  and  8   b  for press-holding the electric wire  7  through a sheath  7   a  thereof in intersecting relation to an axis (centerline) of the electric wire  7 , and three press-connecting blades  9  each for cutting the sheath  7   a  of the electric wire  7  to press-contact and hold a conductor  7   b  of the electric wire in a direction, intersecting the axis of the electric wire, to be electrically connected to the conductor  7   b.    
     The pair of retaining piece portions  8   a  an  8   b  of the barrel portion  8  are formed by stamping part of opposed side plates  2   a  of the metal sheet  2 . The press-connecting blades  9  are formed by cutting part of the side plates  2   a  and then by bending these stamped portions inwardly from stamped openings  2   b.    
     As shown in FIG. 4, each of the press-connecting blades  9  has a pair of bladed, tapering guide surfaces  9   a  which are formed at an upper end portion thereof, and are slanting downwardly toward the axis of the electric wire  7 . The bladed, tapering guide surface  9   a  has an edge  9   b  formed along its slanting surface by cutting. 
     The press-connecting blade  9  has a pair of opposed inner surfaces  9   c  and  9   c  which extend downwardly toward a bottom wall  2   c  respectively from the bladed, tapering guide surfaces  9   a,  with a gap G formed therebetween, the gap G being smaller than the diameter d of the conductor  7   b.    
     When the electric wire  7  is press-fitted into each press-connecting blade  9  in a direction of arrow A as shown in FIGS. 1 and 4, the edges  9   b  cut the sheath  7   a  of the electric wire  7 , while gradually compressing and deforming the outer diameter of the electric wire  7  by the pair of bladed, tapering guide surfaces  9   a.  When the electric wire  7  is further press-fitted, the edges  9   b  completely cut the sheath  7   a.    
     The gap G is thus smaller than the diameter d of the conductor  7   b  (i.e., G&lt;d), and in this case, the conductor  7   b,  comprising a stranded wire comprised of thin wires twisted together, is deformed into a vertically-spread shape by the downwardly-extending inner surfaces  9   c,  as shown in FIG.  4 . The conductor  7   b  is exposed through cut portions of the sheath  7   a,  and directly contacts the downwardly-extending inner surfaces  9   c.    
     As shown in FIGS. 4 and 5, each press-connecting blade  9  is formed by stamping part of the side plates  2   a  and then by bending these stamped portions inwardly. Therefore, a width W of each downwardly-extending inner surface  9   c  for contact with the conductor  7   b  is equal to the thickness of the side plate  2   a.    
     Therefore, the area S of contact of each downwardly-extending inner surface  9   c  with the conductor  7   b  is expressed by S=W×L (L: a length of contact of the downwardly-extending inner surface with the conductor). 
     The press-connecting terminal  1  of this embodiment has the three pairs of downwardly-extending inner surfaces  9   c,  and each pair of inner surfaces  9   c  contact the opposite sides of the conductor  7   b,  respectively. Therefore, the total contact area S T  of the downwardly-extending inner surfaces  9   c  is expressed by S T =2n×W×L (n: the number of press-connecting blades). 
     Therefore, in the press-connecting terminal  1  of this embodiment, on the basis of the width W of each downwardly-extending inner surface  9   c,  the gap G and the number n of the press-connecting blades, the substantial total area S T  of contact of the downwardly-extending inner surfaces  9   c  with the conductor  7   b  is set to a value greater than or equal to the cross-sectional area πd 2 /4 of the conductor  7   b.  With this construction, an electrical resistance, developing between the conductor  7   b  and each press-connecting blade  9 , can be greatly reduced, so that the good electrically-connected condition can be maintained. 
     The angle and length of inclination of the bladed, tapering guide surfaces  9   a,  the length of the edges  9   b  and the gap G between each pair of downwardly-extending inner surfaces  9   c  can be changed in accordance with the outer diameter of the electric wire  7  and the diameter d of the conductor  7   b  so that the functions of the press-connecting blades  9  to deform, cut, press-contact and hold the electric wire  7 , as well as the electrical connection of the press-connecting blades to the electric wire, can be suitably adjusted. 
     As described above, in the press-connecting terminal of the present invention, the press-connecting blade has the pair of opposed inner surfaces extending downwardly respectively from the pair of bladed, tapering guide surfaces which are slanting inwardly downwardly, and the gap, formed between the pair of downwardly-extending inner surfaces, is smaller than the diameter of the conductor of the electric wire. On the basis of at least one of the width of each of the downwardly-extending inner surfaces, the size of the gap, and the number of the downwardly-extending inner surfaces, the effective total area of contact of the downwardly-extending inner surfaces with the conductor is set to a value not smaller than the cross-sectional area of the conductor. 
     Therefore, the functions of the press-connecting blades to press-contact and hold the conductor, as well as the electrical connection of the press-connecting blades to the conductor, can be suitably achieved. Therefore, those members around the press-connecting portion are prevented from being subjected to deterioration, improper contact and so on by heat produced by the electrical resistance developing between the conductor and each press-connecting blade, and therefore the safety of the vehicle is positively prevented from being affected.