Abstract:
A press-fit connector terminal includes: a terminal body having a length sufficient to pass through an electrically conductive through-hole formed through a circuit substrate; and a contact unit arranged around the terminal body so as to surround therewith about a central axis of the terminal body, the contact unit being formed capable of expanding/contracting in a radial direction around the central axis. The contact unit has rigidity lower than that of the terminal body, the terminal body is made of material with electrical conductivity greater than that of the contact unit; and when the terminal body and the contact unit are integrally inserted into the through-hole, a gap exists between the terminal body and the contact unit so that the contact unit is movable relative to the terminal body in the radial direction within the through-hole.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a press-fit connector terminal to be inserted into an electrically conductive through-hole formed through a circuit substrate, and more particularly to a press-fit connector terminal through which a large amount of current can pass. 
     Description of the Related Art 
     In these days, there is an increasing demand for a press-fit connector terminal through which a current in the range of about 60 to 80 A/pin can run. In order for a press-fit connector terminal to make it possible to allow a much current to run there-through, the press-fit connector terminal is necessary to have a large cross-section. That is, a press-fit connector terminal is necessary to be made of an electrically conductive sheet having an increased thickness. However, a press-fit connector terminal made of a sheet having an increased thickness is accompanied with a problem that since spring performance of a press-fit connector terminal is deteriorated, and hence, the press-fit connector terminal cannot avoid being solid, resulting in that when the press-fit connector terminal is inserted into a through-hole formed through a circuit substrate, it is afraid that the press-fit connector terminal may damage an inner surface of the through-hole and/or a circuit substrate. 
     For instance, Japanese Patent Application Laid-open on No. 2009-21016 discloses a press-fit terminal. A press-fit terminal having a relatively large thickness is illustrated in FIGS. 4 and 5 thereof. It is considered that when the press-fit terminal is inserted into a through-hole, elastic contact pieces defining the press-fit terminal contact with an inner surface of the through-hole, and act as a spring to the through-hole. 
     Furthermore, since an inner surface of the through-hole has a broad area where contact pressure is received from the elastic contact pieces, it is considered that it is possible to prevent the through-hole and a resin-embedded portion of the circuit substrate from being creep-deformed due to an elastic reaction force caused by the elastic contact pieces. 
     As mentioned above, if a press-fit connector terminal is designed to have an increased thickness in order to allow a large amount of current to run there-through, the press-fit connector terminal will be accompanied with a problem that since the spring performance thereof is deteriorated, and hence, the press-fit connector terminal cannot avoid from being solid, resulting in that when the press-fit connector terminal is inserted into a through-hole formed through a circuit substrate, it is afraid that the press-fit connector terminal may damage an inner surface of the through-hole and/or a circuit substrate. 
     Since the press-fit terminal suggested in  FIGS. 4 and 6  of the above-identified Publication does not have a floating structure, when the press-fit terminal is inserted into a through-hole, there occurs fluctuation in contact pressure exerted by the elastic contact pieces onto an inner surface of a through-hole, resulting in deterioration in stability in connection therebetween. 
     SUMMARY OF THE INVENTION 
     In view of the above-mentioned problems in the conventional press-fit connector terminals, an object of the present invention is to provide a press-fit connector terminal capable of allowing a relatively large amount of current to run there-through, not damaging a circuit substrate, and providing excellent stability in connection between itself and a through-hole. 
     A first aspect of the present invention provides a press-fit connector terminal, comprising: a terminal body having a length sufficient to pass through an electrically conductive through-hole formed through a circuit substrate; and a contact unit arranged around the terminal body so as to surround therewith about a central axis of the terminal body, the contact unit being formed capable of expanding/contracting in a radial direction around the central axis, wherein: the contact unit has rigidity lower than that of the terminal body; the terminal body is made of material with electrical conductivity greater than that of the contact unit; and when the terminal body and the contact unit are integrally inserted into the through-hole, a gap exists between the terminal body and the contact unit so that the contact unit is movable relative to the terminal body in the radial direction within the through-hole. 
     According to the above structure, the contact unit can have a function as acting as a press-fit terminal, ensuring that when the press-fit connector terminal is inserted into the through-hole of the circuit substrate, the press-fit connector terminal does not damage the circuit substrate and/or an inner surface of the through-hole, and further ensuring stable connection between the press-fit connector terminal and the through-hole. 
     In addition, the contact unit is movable relative to the terminal body within the through-hole. Thus, the contact unit and the terminal body can have a floating structure. This ensures that when the press-fit connector terminal is fit into the through-hole of the circuit substrate, even if the press-fit connector terminal and the through-hole axially deviate from each other, the floating structure absorbs the axial deviation to thereby equalize contact pressure between the contact unit and the inner surface of the through-hole, ensuring stable connection between the press-fit connector terminal and the through-hole. 
     A second aspect of the present invention provides, in addition to the first aspect, wherein the contact unit includes a plurality of contact pieces arranged around the terminal body to outwardly protrude. 
     A third aspect of the present invention provides, in addition to the first aspect, further comprising first and second binders surrounding the terminal body at distal and proximal ends of the contact unit, wherein: each of the first and second binders has a C-shaped cross-section; and the contact pieces are connected to the first and second binders. 
     A fourth aspect of the present invention provides, in addition to the third aspect, further comprising a cover situated adjacent to the first binder, wherein the cover covers a distal end of the terminal body. 
     A fifth aspect of the present invention provides, in addition to the fourth aspect, wherein the cover includes: a flat portion; and a plurality of extensions extending in a common direction from an outer periphery of the flat portion; one of the extensions is connected to the contact unit through the first binder; and the terminal body is bonded at a top surface thereof with a lower surface of the flat portion such that the contact unit is swingable relative to the terminal body around the top surface of the terminal body. 
     A sixth aspect of the present invention provides, in addition to the third aspect, further comprising: a support portion made of an electrically conductive material; and a connecting portion, wherein: the terminal body stands on an upper surface of the support portion; the connecting portion extends towards the support portion from the second binder; and the connecting portion is bonded to a side of the support portion such that there is a gap generated between the second binder and an upper surface of the support portion. 
     A seventh aspect of the present invention provides, in addition to the sixth aspect, wherein: an elastically deformable boundary portion is formed between the second binder and the connecting portion; and the boundary portion is positioned on a level with the gap. 
     An eighth aspect of the present invention provides, in addition to the sixth aspect, wherein the support portion is constituted of two electrically conductive sheets bonded to each other at an end thereof and overlapping one on another. 
     A ninth aspect of the present invention provides, in addition to the sixth aspect, wherein the terminal body and the support portion are made of a material having electrical conductivity of at least 99.9% IACS. 
     The advantages obtained by the aforementioned present invention will be described hereinbelow. 
     The press-fit connector terminal according to the present invention is able to allow a relatively large amount of current to run there-through, exert no damages to a circuit substrate, and provide stable connection between itself and a circuit substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the press-fit connector terminal according to the first embodiment of the present invention; 
         FIG. 2  is a perspective view of the press-fit connector terminal illustrated in  FIG. 1 ; 
         FIG. 3  is a front view of the press-fit connector terminal illustrated in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view taken along the line A-A shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view taken along the line B-B shown in  FIG. 3 ; 
         FIG. 6  is a cross-sectional view taken along the line C-C shown in  FIG. 3 ; 
         FIG. 7  is a broken perspective view of the press-fit connector terminal illustrated in FIG.  1 ; 
         FIG. 8  is a broken perspective view of the press-fit connector terminal illustrated in  FIG. 1 ; 
         FIG. 9  is a perspective view of a terminal module including the press-fit connector terminal illustrated in  FIG. 1 ; 
         FIG. 10  is a perspective view showing a step of connecting the terminal module illustrated in  FIG. 9  to a partially illustrated circuit substrate; 
         FIG. 11  is a perspective view illustrating the terminal module illustrated in  FIG. 9  having been connected to a partially illustrated circuit substrate; 
         FIG. 12  is a view seen in a direction indicated with an arrow D shown in  FIG. 11 ; 
         FIG. 13  is a partial cross-sectional view taken along the line E-E shown in  FIG. 12 ; 
         FIG. 14  is a partial cross-sectional view taken along the line F-F shown in  FIG. 12 ; 
         FIG. 15  illustrates the press-fit connector terminal illustrated in  FIG. 1  being a condition of floating; 
         FIG. 16  is a cross-sectional view taken along the line G-G shown in  FIG. 15 ; 
         FIG. 17  is a perspective view of the press-fit connector terminal according to the second embodiment of the present invention; 
         FIG. 18  is a perspective view of the press-fit connector terminal illustrated in  FIG. 17 ; 
         FIG. 19  is a right side view of the press-fit connector terminal illustrated in  FIG. 17 ; 
         FIG. 20  is a broken perspective view of the press-fit connector terminal illustrated in  FIG. 17 ; and 
         FIG. 21  is a broken perspective view of the press-fit connector terminal illustrated in  FIG. 17 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A press-fit connector terminal  100  according to the first embodiment of the present invention is explained hereinbelow with reference to  FIGS. 1 to 16 . In the specification, a direction indicated with an arrow X illustrated in  FIG. 1  indicates a left-right or a horizontal direction, a direction indicated with an arrow Y illustrated in  FIG. 1  indicates an up-down or a vertical direction, and a direction indicated with an arrow Z illustrated in  FIG. 1  indicates a front-rear direction. 
     As illustrated in  FIGS. 1 to 3 and 10 , the press-fit connector terminal  100  according to the first embodiment of the present invention includes a pin section  10 , a terminal body  11 , a contact unit  30 , and a cover  34 . 
     The pin section  10  is fabricated by steps of punching a metal sheet having electrical conductivity into a predetermined shape, and pressing the punched metal sheet, including collapsing and bending steps. The pin section  10  includes a support portion  12  comprised of a metal sheet folded into a U-shape, an elbow portion  14  continuous to a lower surface of the support portion  12 , and a flat connection portion  13  backwardly extending from the elbow portion  14 . A bonding wire (not illustrated) is connected at an end thereof to the flat connection portion  13 . 
     The terminal body  11  stands on an upper surface of the support portion  12 . As illustrated in  FIG. 4 , the terminal body  11  includes a cylindrical portion and an upper portion  11   b  formed continuous to the cylindrical portion and having a shape of a truncated cone. 
     The terminal body  11  is designed to have a length sufficient to pass through an electrically conductive through-hole  301  (see  FIG. 10 ) formed through a circuit substrate  300 . 
     The contact unit  30  is arranged around the terminal body. The contact unit  30  is able to elastically contact with an inner surface  302  (see  FIG. 10 ) of the through-hole  301 . 
     The contact unit  30  and the pin section  10  are made of a material having electrical conductivity and acting as a spring to a greater degree than the terminal body  11 . 
     The pin section  10  and the terminal body  11  are made of a material having a higher electrical conductivity than the same of the contact unit  30 . 
     The pin section  10  and the terminal body  11  can be made of any material. For instance, the pin section  10  and the terminal body  11  are made preferably of copper, particularly pure copper, having electrical conductivity of 99.9% IACS or greater. 
     The terminal body  11  and the contact unit  30  are designed to have such a size that when the press-fit connector terminal  100  is fit into the through-hole  301 , between the terminal body  11  and the contact unit  30  is generated a gap S sufficient for the contact unit  30  to be able to come close to and go away from the said terminal body  11 . 
     The contact unit  30  is connected to the terminal body  11  such that when the press-fit connector terminal  100  is fit into the through-hole  301 , the contact unit  30  is movable relative to the terminal body  11 , as later explained in detail. 
     The contact unit  30  is fabricated by bending a single metal sheet having elasticity. The contact unit  30  is comprised of a plurality of contact pieces  31  arranged around the terminal body  11  or an imaginary center line  30   c  of the contact unit  30 . Each of the contact pieces  31  is bent by an obtuse angle or outwardly protrudes at a center thereof in a length-wise direction thereof. Each of the contact pieces  31  is elastically deformable, specifically elastically expandable and shrinkable, relative to the terminal body  11  or the imaginary center line  30   c.    
     The press-fit connector terminal  100  further includes first and second C-shaped binders  32  and  33  surrounding the terminal body at distal (upper) and proximal (lower) ends of the contact unit  30 . The contact pieces  31  are connected at upper and lower ends thereof to the first and second binders  32  and  33 . 
     The cover  34  is situated above the first binder  32  to cover the upper portion  11   b  of the terminal body  11  therewith. 
     As illustrated in  FIGS. 1 to 4 , the cover  34  includes a flat portion  34   a  extending in parallel with a flat top surface  11   a  of the upper portion  11   b  of the terminal body  11 , and a plurality of extensions  34   b  downwardly extending from an outer periphery of the flat portion  34   a  towards the first binder  32  such that the extensions  34   b  surround the upper portion  11   b  of the terminal body  11 . The extensions  34   b  spread like a skirt and are equally spaced away from one another. One of the extensions  34   b  is connected to the first binder  32 . 
     The press-fit connector terminal  100  illustrated in  FIGS. 1 and 2  is fabricated by inserting the terminal body  11  into the contact unit  30 , as illustrated in  FIGS. 7 and 8 , and then, the cover  34  is welded at a lower surface of the flat portion  34   a  to the flat top surface  11   a  of the upper portion  11   b  of the terminal body  11  in an welding area W, as illustrated in  FIG. 4 . In the press-fit connector terminal  100 , a center line  11   c  of the terminal body  11  and the imaginary center line  30   c  of the contact unit  30  are coincident with each other. As illustrated in  FIGS. 3 and 4 , an upper surface of the support portion  12  and a lower surface of the second binder  33  are spaced away from each other. 
     The terminal body  11  and the cover  34  may be joined to each other by caulking in place of the above-mentioned welding. 
     As illustrated in  FIG. 9 , a terminal module  50  is completed by fixing the support portion  12  and the elbow portions  14  of a plurality of the press-fit connector terminals  100  into a constant posture by means of a base  40  made of an electrically insulative resin. The terminal module  50  is fabricated by forming the base  40  integrally with the press-fit connector terminals  100 . As an alternative, the base  40  may be fabricated separately from the press-fit connector terminals  100 . 
     In the press-fit connector terminals  100 , since the pin section  10  and the terminal body  11  are made of a material having higher electrical conductivity than the same of the contact unit  30 , the press-fit connector terminal  100  is able to allow a relatively large of amount of a current to run there-through. Furthermore, the contact unit  30  is made of an electrically conductive material acting as a spring to a greater degree than the pin section  10  and the terminal body  11 . Specifically, the contact pieces  31  defining the contact unit  30  are designed to be elastically expandable and shrinkable relative to the terminal body  11  or the imaginary center line  30   c , and accordingly, the contact unit  30  has a function as acting as a press-fit terminal, ensuring that when the press-fit connector terminal  100  is inserted into the through-hole  301  of the circuit substrate  300 , as illustrated in  FIG. 10 , the press-fit connector terminal  100  does not damage the circuit substrate  300  and/or the inner surface  302  of the through-hole  301 , and further ensuring stable connection between the press-fit connector terminal  100  and the through-hole  301 . 
     As illustrated in  FIGS. 11 to 14 , the terminal body  11  and the contact pieces  31  of the contact unit  30  are designed to have such a size that when the press-fit connector terminal  100  is fit into the through-hole  301 , between the terminal body  11  and the contact pieces  31  is generated a gap S sufficient for the contact pieces  31  to be able to come close to and go away from the terminal body  11 , and the terminal body  11  and the contact unit  30  are joined to each other at the welded area W situated above the circuit substrate  300 . That is, the cover  34  is joined to the upper portion  11   b  of the terminal body  11  passing through the through-hole  301  and protruding beyond the circuit substrate  300 . Thus, as illustrated in  FIGS. 15 and 16 , the extensions  34   b  of the contact unit  30  are swingable relative to the terminal body  11  around the welded area W. Namely, the contact unit  30  defines an elastically deformable floating structure movable relative to the terminal body  11 . 
     Accordingly, when the press-fit connector terminal  100  is inserted into the through-hole  301 , even if the press-fit connector terminal  100  and the through-hole  301  of the circuit substrate  300  axially deviate from each other, the extensions  34   b  of the contact unit  30  swing around the welded area W relative to the terminal body  11  to thereby absorb the axial deviation of the press-fit connector terminal  100  from the through-hole  301 , as illustrated in  FIGS. 15 and 16 . Thus, contact pressure between the contact pieces  31  of the contact unit  30  and the inner surface  302  of the through-hole  301  is uniformized, ensuring stable connection between the press-fit connector terminal  100  and the through-hole  301 . 
     Second Embodiment 
     A press-fit connector terminal  200  according to the second embodiment of the present invention is explained hereinbelow with reference to  FIGS. 17 to 21 . 
     Parts or elements that correspond to those of the press-fit connector terminal  100  illustrated in  FIGS. 1 to 16  have been provided with the same reference numerals, operate in the same manner as corresponding parts or elements in the press-fit connector terminal  100 , unless explicitly explained hereinbelow, and are not explained. 
     As illustrated in  FIGS. 17 and 18 , the press-fit connector terminal  200  includes a cover  35  having a shaped of a truncated cone. The cover  35  is continuous to and located on the first binder  32 . The cover  35  is formed at a top end thereof with a through-hole  36  extending in a direction of an imaginary center line  30   c.    
     The press-fit connector terminal  200  further includes a T-shaped connecting portion  37  extending towards a pin section  20  from a part of the second binder  33 , that is, extending in a direction opposite to a direction in which the contact pieces  31  extend from the second binder  33  towards the first binder  32 . 
     As illustrated in  FIGS. 19 and 20 , a terminal body  21  stands on an upper surface of the support portion  12  of the pin section  20 . The terminal body  21  includes a cylindrical portion and an upper portion  21   b  formed continuous to the cylindrical portion and having a shape of a truncated cone. The upper portion  21   b  has a flat top surface  21   a.    
     The terminal body  21  is designed to have a length (a length between an upper surface of the support portion  12  and the flat top surface  21   a ) smaller than a length of a contact unit  30 A in a direction of the imaginary center line  30   c  (or a distance between the first and second binders  32  and  33 ). 
     As illustrated in  FIGS. 20 and 21 , the press-fit connector terminal  200  is completed by inserting the terminal body  21  of the pin section  20  into the contact unit  30 A, and welding the connecting portion  37  onto a side of the support portion  12 . As illustrated in  FIG. 19 , there is a gap between an upper surface of the support portion  12  and a lower surface of the second binder  33 . The terminal body  21  and the cover  35  may be joined to each other by caulking in place of the above-mentioned welding. 
     As illustrated in  FIGS. 17 to 19 , there is formed the gap S in the contact unit  30 A between the terminal body  21  and the contact pieces  31 . After the press-fit connector terminal  200  has been inserted into the through-hole  301 , the gap S is maintained to exist between the terminal body  21  and the contact pieces  31  such that the contact pieces  31  are able to be deformed towards and away from the terminal body  21 . 
     As illustrated in  FIG. 19 , there is further formed a space R between the flat top surface  21   a  of the terminal body  2   i  and a lower surface of the cover  35 . Similarly to the contact unit  30  illustrated in  FIG. 1 , the contact unit  30 A has a press-fit function. 
     As illustrated in  FIG. 18 , the press-fit connector terminal  200  includes an elastically deformable boundary portion  38  formed between the second binder  33  and the connecting portion  38 . As illustrated in  FIG. 19 , the boundary portion  38  is positioned on a level with the gap S. 
     Thus, the contact unit  30 A can be elastically deformed around the boundary portion  38 . In other words, the contact unit  30 A is able to swing around the boundary portion  38  in a thickness-wise direction of the boundary portion  38 . Thus, the contact unit  30 A has a floating in structure, similarly to the contact unit  30  of the press-fit connector terminal  100  illustrated in  FIG. 1 . 
     It should be noted that the press-fit connector terminals  100  and  200  having been described with reference to  FIGS. 1 to 21  are just examples of the present invention. It is to be understood that the subject matter encompassed by way of the present invention is not to be limited to the press-fit connector terminals  100  and  200  as specific embodiments. On the contrary, it is intended for the subject matter of the present invention to include all alternatives, modifications and equivalents as can be included within the spirit and scope of the following claims. 
     INDUSTRIAL APPLICABILITY 
     The press-fit connector terminal according to the present invention can be broadly employed in fields such as an electric/electronic industry and an automobile industry, as a connector to be inserted into a through-hole of a circuit substrate through which a large amount of current runs. 
     The entire disclosure of Japanese Patent Application No. 2014-245219 filed on Dec. 3, 2014 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.