Patent Publication Number: US-2015064989-A1

Title: Connection structure for screw clamp terminal

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to and incorporates by reference the entire contents of Japanese Patent Application No. 2013-181737 filed in Japan on Sep. 3, 2013. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a connection structure for a screw clamp terminal applied to, for example, an electrical junction box and fastened by a bolt to be electrically connected to a bus bar. 
     2. Description of the Related Art 
     A conventional connection structure for a screw clamp terminal is known, for example, in Japanese Patent Application Laid-open No. 2010-28919. 
     Specifically, in the connection structure for a screw clamp terminal according to this patent literature, as illustrated in  FIG. 6  and  FIG. 7 , a terminal  1  includes an electrical contact part  5  and a coupling section  6 . The electrical contact part  5  is bifurcated approximately in the shape of letter U to form a bolt shaft insertion section  5   a  into which a shaft  3   a  of a bolt  3  is inserted. The electrical contact part  5  is fastened by a head  3   b  of the bolt  3  and a nut  4  thereby to establish electrical connection with a bus bar  2 . The coupling section  6  stands upright in the shape of an arch formed by connecting the front ends of the bifurcated electrical contact part  5 . The coupling section  6  has an opening formed as a bolt head insertion section  6   a  into which the head  3   b  of the bolt  3  is inserted. The coupling section  6  couples the front ends of the bifurcated electrical contact part  5  with each other to prevent expansion deformation caused at the front end side of the electrical contact part  5  due to torque action during bolt fastening (hereinafter abbreviated as “expansion deformation based on fastening torque action”). 
     However, the conventional connection structure for a screw clamp terminal causes problems such as increasing the size of the terminal  1  because of the formation of the coupling section  6  and increasing the number of production processes because of the complicated shape. 
     In the conventional connection structure for a screw clamp terminal, the connection of the terminal  1  requires positioning using the coupling section  6 , for example, by providing a not-shown electrical junction box with a section for temporarily holding the terminal  1  with the coupling section  6  interposed in order to avoid connection failure between the terminal  1  and the bus bar  2  due to displacement based on the torque action during bolt fastening (hereinafter abbreviated as “connection failure based on the fastening torque action”). The connecting operation of the terminal  1  is thus cumbersome. 
     SUMMARY OF THE INVENTION 
     The present invention is devised in view of such technical problems and aims to provide a connection structure for a screw clamp terminal that can eliminate positioning of the terminal for connection while reducing size increase and cost increase of the terminal. 
     It is an object of the present invention to at least partially solve the problems in the conventional technology. 
     According to one aspect of the present invention, a connection structure for a screw clamp terminal having an electrical contact part through which a bolt insertion hole penetratingly formed communicating with outside through a notch, a shaft of a bolt being inserted into the bolt insertion hole through the notch, a head of the bolt fastening the electrical contact part to a member to be connected to establish electrical connection, the connection structure includes an engagement projection provided in an outer peripheral region of the bolt insertion hole, the engagement projection having a convex conical surface; and an engagement depression provided on an inner surface of the head of the bolt and disposed opposed to the engagement projection, the engagement depression having a concave conical surface corresponding to the convex conical surface and being capable of engaging with the engagement projection through the concave conical surface, wherein the engagement projection and the engagement depression are engaged with each other during fastening of the bolt. 
     According to another aspect of the present invention, a connection structure for a screw clamp terminal having an electrical contact part through which a bolt insertion hole penetratingly formed communicating with outside through a notch, a shaft of a bolt being inserted into the bolt insertion hole through the notch, a nut being screwed onto the shaft to fasten the electrical contact part to a member to be connected to establish electrical connection, the connection structure includes an engagement projection provided in an outer peripheral region of the bolt insertion hole, the engagement projection having a convex conical surface; and an engagement depression provided on an inner surface of the nut and disposed opposed to the engagement projection, the engagement depression having a concave conical surface corresponding to the convex conical surface and being capable of engaging with the engagement projection through the concave conical surface, wherein the engagement projection and the engagement depression are engaged with each other during fastening of the nut. 
     During bolt fastening, because of the engagement structure of the engagement projection formed on the outer surface of the terminal (electrical contact part) and the engagement depression formed on the inner surface of the bolt head, the head of the bolt allows the electrical contact part to be pulled toward the bolt center and pushed down so as to suppress enlargement of the notch as the bolt is fastened (advanced). 
     The connection structure is also applicable to a structure in which a terminal is fastened (connected) to a member to be connected by tightening a nut rather than a bolt. Also in this case, the same operation effects as in the bolt fastening described above are achieved. 
     The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a connection structure for a screw clamp terminal according to the present invention in a state before a terminal is slipped onto a bolt; 
         FIG. 2  is a cross-sectional view along line A-A in  FIG. 1 ; 
         FIG. 3  is a perspective view illustrating the connection structure for a screw clamp terminal according to the present invention in a state in which the terminal is fastened; 
         FIG. 4  is a cross-sectional view along line B-B in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view corresponding to  FIG. 4  illustrating a modification of the connection structure for a screw clamp terminal according to the present invention; 
         FIG. 6  is a perspective view illustrating a conventional connection structure for a screw clamp terminal in a state before a terminal is slipped onto a bolt; and 
         FIG. 7  is a cross-sectional view corresponding to  FIG. 4  illustrating a state in which the terminal is fastened. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of a connection structure for a screw clamp terminal according to the present invention will be described in details below with reference to the figures. In the present embodiment, the connection structure for a screw clamp terminal is applied to terminal connection in an electrical junction box (fuse box) by way of example. The configuration of the electrical junction box is well known per se, and a specific description of the electrical junction box will be omitted. 
     As illustrated in  FIG. 1  and  FIG. 2 , a housing  10  of an electrical junction box is formed of an insulative resin material. A nut  11  is buried in the housing  10  such that the front end thereof faces a surface  10   a  in a state in which movement in the Z-axis direction and rotation around the Z-axis in the figures are restricted, that is, in a fixed state. A plate-shaped bus bar  12  serving as a member to be connected is arranged on the surface  10   a  of the housing  10 . A hexagonal bolt (hereinafter simply referred to as “bolt”)  13  is screwed in the nut  11 . The bolt  13  has a shaft  13   a  inserted into a through hole  12   a  provided in the bus bar  12  to fasten the bus bar  12  and a terminal  20  connected thereto. 
     An electric wire  14  is crimped to a well-known electric wire connection part  21  provided at the rear end side of the terminal  20 . An electrical contact part  22  approximately in the shape of a letter C formed at the front end side of the terminal  20  is fastened to the bas bar  12  using the bolt  13  and the nut  11 , thereby establishing electrical connection with the bus bar  12 . The electrical contact part  22  has a bolt insertion hole  23  approximately at the center position thereof into which the shaft  13   a  of the bolt  13  can be inserted. The electrical contact part  22  has a notch  24  formed at the front end thereof so as to be cut along the longitudinal direction (the X-axis direction in the figures) of the terminal  20 . The notch  24  provides direct communicative connection between the bolt insertion hole  23  and the outside to allow the bolt insertion hole  23  to be slipped onto the shaft  13   a  from the outside. 
     In the outer peripheral region of the bolt insertion hole  23  in the electrical contact part  22 , an engagement projection  25  is provided, which is formed by deforming the hole edge of the bolt insertion hole  23  so as to push upward so that the hole edge of the bolt insertion hole  23  protrudes in the Z-axis positive direction in the figure. A convex conical surface  25   a  formed in a conical tapered shape is provided on the outer periphery of the engagement projection  25 . On the inner surface of a head  13   b  of the bolt  13  that is opposed to the engagement projection  25  during the fastening of the electrical contact part  22  with the bus bar  12 , an engagement depression  15  is provided, which has a concave conical surface  15   a  corresponding to the convex conical surface  25   a  and can be engaged with the engagement projection  25 . As described above in the connection structure for the terminal  20  in the present embodiment, the engagement depression  15  and the engagement projection  25  can be engaged with each other during the fastening of the terminal  20  (the electrical contact part  22 ) and the bus bar  12  by the bolt  13  (see  FIG. 4 ). 
     The connection procedure of the terminal  20  will be described below with reference to  FIG. 1  to  FIG. 4 , and characteristic effects of the present invention will also be described.  FIG. 1  and  FIG. 2  illustrate a state before the terminal  20  is connected to the bus bar  12 , and  FIG. 3  and  FIG. 4  illustrate a state after the terminal  20  is connected to the bus bar  12 . 
     Specifically, to connect the terminal  20  to the bus bar  12 , the terminal  20  having the electric wire  14  crimped thereto as described above is slipped along the longitudinal direction thereof (the X-axis direction in the figures) onto the shaft  13   a  of the bolt  13  inserted into the bus bar  12  disposed on the electrical junction box in advance and screwed into the nut  11  buried in the electrical junction box in advance. The shaft  13   a  is then engaged into the bolt insertion hole  23  through the notch  24 . 
     The bolt  13  is tightened with a not-shown fastening tool such as an impact wrench, whereby the terminal  20  (the electrical contact part  22 ) and the bus bar  12  are fastened and connected with each other. Here, in the present embodiment, when the bolt  13  is tightened, the engagement depression  15  of the bolt  13  engages with the engagement projection  25  of the terminal  20 , and this engagement structure brings about a wedge effect to allow the terminal  20  (the electrical contact part  22 ) to be gradually pulled toward the center of the bolt  13 . This inevitably ensures connection with the bus bar  12  at an appropriate position even without positioning the terminal  20  as in the conventional example, thereby avoiding connection failure based on the fastening torque action. At the same time, the electrical contact part  22  is pushed down such that the head  13   b  of the bolt  13  suppresses enlargement of the notch  24  based on the wedge effect brought about by the engagement structure. Accordingly, expansion deformation of the electrical contact part  22  based on the fastening torque action, that is, enlargement deformation of the notch  24  as in the conventional example can also be suppressed. 
     As described above, in the connection structure for the terminal  20  according to the present embodiment, the engagement depression  15  of the bolt  13  is engaged with the engagement projection  25  of the terminal  20  during bolt fastening, so that connection failure based on the fastening torque action can be inevitably avoided, thereby achieving easy and reliable connection of the terminal  20 . 
     In the present embodiment, the wedge effect also inevitably suppresses enlargement deformation of the notch  24  caused by the torque action during bolt fastening, thereby avoiding connection failure, detachment, and other inconvenience of the terminal  20  due to enlargement deformation of the notch  24 . 
     Such a connection structure for the terminal  20  can be provided in such a simple configuration as merely providing the engagement projection  25  on the terminal  20  side and the engagement depression  15  on the bolt  13  side. Accordingly, the terminal  20  is unlikely to increase in size, and cost increase of the terminal  20  can be suppressed. 
       FIG. 5  illustrates a modification of the foregoing embodiment, in which the relation of arrangement between the bolt  13  and the nut  11  in the foregoing embodiment is reversed. In this modification, the configuration other than the relation of arrangement between the bolt  13  and the nut  11  is the same as the foregoing embodiment. The same configuration as the foregoing embodiment is therefore denoted with the same reference signs, and a specific description thereof will be omitted. 
     In this modification, the bolt  13  has its head  13   b  buried in the housing  10  of the electrical junction box and has the shaft  13   a  protruding from the surface  10   a  of the housing  10  toward the Z-axis positive direction in the figure and arranged so as to be inserted into the through hole  12   a  of the bus bar  12  arranged on the surface  10   a  of the housing  10 . The nut  11  is screwed onto the front end of the shaft  13   a . Also in this modification, the electrical contact part  22  of the terminal  20  having the electric wire  14  crimped thereto is slipped onto the shaft  13   a  exposed between the head  13   b  of the bolt  13  and the nut  11  through the notch  24 , in the same manner as in the foregoing embodiment. The nut  11  is fastened to electrically connect the terminal  20  (the electrical contact part  22 ) with the bus bar  12 . 
     Also in this modification, the electrical contact part  22  is pulled toward the center of the bolt  13  and pushed down so as to suppress enlargement of the notch  24  as the nut  11  is fastened (advanced) in the same manner as in the foregoing embodiment. As a result, the same operation effects as in the foregoing embodiment can be achieved. 
     The present invention is not limited to the configuration in the foregoing embodiment or other modifications. The configuration of details not directly pertinent to the configuration of the present invention, such as the configuration of details such as the terminal  20 , the bolt  13 , and the nut  11 , for example, the shape of the bolt insertion hole  23  and the notch  24 , as well as the parts directly pertinent to the configuration of the present invention, for example, such as the formation range of the engagement depression  15  and the engagement projection  25  and the angle of the conical surfaces  15   a ,  25   a  can be changed freely in accordance with the specifications or requirements of applications within a range that does not depart from the spirit of the invention. 
     According to the present invention, the terminal (electrical contact part) is pulled toward the bolt center as the bolt is fastened (advanced), so that connection at an appropriate position is inevitably ensured without performing positioning of the terminal. 
     Because of the engagement structure, the electrical contact part is also pushed down so as to suppress enlargement of the notch as the bolt is fastened (advanced), so that expansion deformation based on the fastening torque action on the electrical contact part, that is, enlargement deformation of the notch is suppressed, and connection failure, detachment, or other inconvenience of the terminal based on the deformation can be avoided. 
     The engagement structure can be provided in such a simple configuration as merely providing an engagement projection on the terminal side and an engagement depression on the bolt side, thereby suppressing not only size increase but also cost increase of the terminal. 
     Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.