Patent Publication Number: US-2010120298-A1

Title: Terminal fitting a wire connection structure and a connecting method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a terminal fitting and a wire connection structure and to a connecting method therefor. 
     2. Description of the Related Art 
     Japanese Unexamined Patent Publication No. 2005-222815 discloses a structure for connecting a terminal fitting. The terminal fitting includes a wire barrel in the form of an open barrel, in which a pair of crimping pieces stand up from the opposite left and right edges of a bottom wall. The structure also includes a front end portion of a wire including a conductor formed by twisting a plurality of metal thin wires. In the wire barrel portion, the crimping pieces of the wire barrel surround and compress the conductor so that whereby the wire is electrically connected. In a connected state, a front end portion of the conductor projects forward from the front end of the wire barrel portion. 
     An oxide film will form if the conductor in the wire is made of aluminum. Thus, the wire barrel must be fastened more tightly to remove an oxide film. However, if the wire barrel portion is fastened more tightly, the metal thin wires constituting the conductor will loosen and deform during the crimping process. Some of the spread metal thin wires will bend toward a side opposite to the bottom wall. These bent-up metal thin wires may interfere with other members. 
     The present invention was developed to suppress or reduce the formation of a bent-up front end portion of a conductor projecting from a wire barrel portion. 
     SUMMARY OF THE INVENTION 
     The subject invention relates to a connection structure for a terminal fitting, with a wire barrel portion in the form of at least one open barrel, in which one or more, and, preferably a pair, of crimping pieces project from a base wall. The crimping pieces compress a conductor of a wire while at least partly surrounding the conductor in the wire barrel portion to electrically connect the conductor. A front end portion of the conductor projects forward from the front end of the wire barrel in a crimped state. One or more pressing portions are formed in or near one or more front end portions of one or more ceiling walls of the crimping pieces located at a side of the conductor substantially opposite to the base wall. The pressing portions are closer to the base wall than rear end areas of the crimping pieces. 
     The height of the front end portion of the conductor projecting from the front end of the wire barrel from the base wall is reduced due to the displacement of the conductor toward the base wall. Thus, even if the metal thin wires are deformed by the crimping, the height of the bent-up portions of the conductor will be reduced or suppressed. 
     The pressing portions at the front end of the upper walls of the crimping pieces are inclined to approach the base or bottom wall toward the front. As a result, the front end portion of the conductor also projects toward the base or bottom wall from the front end of the wire barrel. Thus, the height of the deformed front end portion of the conductor can be suppressed more effectively. 
     The angle of inclination of the pressing portions preferably is substantially constant over the entire lengths of the pressing portions. 
     Still further preferably, the pressing portions are formed into recesses by hammering parts of the upper walls of the crimping pieces except the opposite widthwise end portions toward the bottom wall, and the opposite widthwise end portions of the front end portions of the upper walls are formed into folded portions projecting toward a side opposite to the bottom wall. 
     If the front end portions of the upper walls of the crimping pieces are deformed over the entire widths to approach the bottom wall upon forming the pressing portions, side walls connecting the upper walls and the bottom wall are deformed outwardly in the width direction by as much as the approach amount of the upper walls toward the bottom wall and the wire barrel portion is widened. In contrast, the folded portions are formed at the opposite widthwise end portions of the upper walls in the present invention and only the parts between the folded portions are formed into the pressing portions by being deformed to approach the bottom wall. Thus, the side walls will not be displaced. 
     The pair of lateral crimping pieces preferably are laterally symmetric. 
     Preferably, one pressing portion is individually formed at each crimping piece of the plurality of crimping pieces. 
     Most preferably, the rear end areas of the crimping pieces behind or adjacent to the pressing portions are substantially parallel to the base wall. 
     The invention also relates to a terminal fitting comprising the above described connection structure and a terminal connecting portion substantially continuous thereto. 
     These and other objects, features and advantages of the present invention will become more apparent upon reading the following detailed description of preferred embodiments and accompanying drawings. It should be understood that even though embodiments are separately described, single features thereof may be combined to create additional embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of one embodiment. 
         FIG. 2  is a plan view of the embodiment. 
         FIG. 3  is a section along X-X of  FIG. 1  without any graphical representation of a conductor of a wire. 
         FIG. 4  is a partial enlarged section showing a state where pressing portions are pressing the conductor obliquely downward toward the front. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A conduction path in accordance with the invention is identified by the numeral  1  in  FIGS. 1 and 2 . The conduction path  1  is formed by connecting a front end portion (left end portion in  FIGS. 1 and 2 ) of a wire  10  with a crimping portion  22  (as a preferred connecting structure) formed at or near a rear end portion of a terminal fitting  20 . 
     The wire  10  is comprised of a conductor  11  formed by twisting a plurality of metal thin wires and an insulation coating  12  at least partly surrounding the conductor  11 . In the front end portion of the wire  10 , the insulation coating  12  is partly removed in preparation for connection with the terminal fitting  20 , whereby a front end portion of the conductor  11  is exposed. Copper or copper alloy, a material having higher rigidity than copper or copper alloy (e.g. aluminum or aluminum alloy) and/or a material having lower electrical conductivity than copper or copper alloy (e.g. aluminum or aluminum alloy) is or may be used as the material for the conductor  11 . 
     The terminal fitting  20  is a female terminal fitting formed by applying, bending, folding, and/or embossing and the like to a conductive (preferably metal) plate material punched or cut out into a specified shape, wherein a front end region serves as a terminal connecting portion  21  in the form of a rectangular tube and a rear end region serves as a crimping portion  22  in the form of at least one open barrel. The terminal connecting portion  21  is of the known form that functions as connection means with a narrow and long tab (not shown) formed on a mating male terminal. It should be understood, however, that the present invention is also applicable to male terminal fittings having a substantially tab-shaped terminal connection portion connectable to a mating female terminal. 
     The rear end of the terminal connecting portion  21  and the front end of the crimping portion  2  are coupled via at least one coupling portion  23 . The coupling portion  23  includes a lower or base plate and two laterally symmetrical side plates or projecting at an angle, preferably substantially at right angles from the lateral edges of the lower plate. Thus, an accommodation space  24  with a substantially open upper side is formed in the coupling portion  23 . 
     The crimping portion  22  includes at least one wire barrel  25  substantially continuous with the rear end of the coupling portion  23  and at least one insulation barrel  31  located behind the wire barrel  25 . The insulation barrel  31  is to be crimped, bent, or folded into connection with a part of the front end of the wire  10  where the insulation coating  12  at least partly surrounding the conductor  11  is provided or still remains. Upon the crimping operation, an automatic machine (not shown) called an applicator is used and the insulation barrel  31  is crimped, bent, or folded into connection with the wire  10  at the same time that the wire barrel  25  is crimped or bent or folded into connection with the conductor  11 . In the crimped state, the wire  10  is pressed over the entire circumference by the insulation barrel  31  and the wire  10  is fixed to the insulation barrel  31  by this pressing. 
     The wire barrel  25  includes a bottom or base wall  26  substantially continuous with the lower plate of the coupling portion  23  and a pair of laterally symmetrical crimping pieces  27  extending from the lateral edge(s) of the bottom wall  26 . This wire barrel  25  is to be crimped, bent, or folded into electrical connection with the front end of the conductor  11  partially exposed by removing the insulation coating  12  near the front of the wire  11 , so that the conductor  11  is fixed. Upon performing the crimping operation, the crimping portion  22  set in an anvil (not shown) of the automatic machine and the conductor  11  placed on the bottom wall  26 . A crimper (not shown) then is lowered to deform the crimping piece(s)  27  to wind them at least partly around the conductor  11  The bottom wall  26  and the pair of crimping pieces  27  are so crimped, bent, or folded so as to at least partly surround the conductor  11  while pressing it. 
     In the crimped state, the front end of the conductor  11  projects forward from the front end edge(s) of the crimping piece(s)  27  (wire barrel portion  25 ) and at least partly contained in the accommodation space  24  enclosed or defined by the lower or base plate and the opposite side plates of the coupling portion  23 . If the conductor  11  is made of aluminum or aluminum alloy, the wire barrel  25  is strongly fastened during the crimping operation to remove oxide films on the outer surfaces of the conductor (preferably of the metal thin wires). In this case, the metal thin wires of the conductor  11  may be loosened and front end portions of the loosened metal thin wires are or may be deformed to spread out in the accommodation space  24  before the wire barrel  24 . The accommodation space  24  is open upward, thus, some of the metal thin wires may be bent to be located above the wire barrel  25 . If a part above the accommodation space  24  serves as a space to arrange another member (e.g. a retainer for retaining the terminal fitting  20  by being engaged with the rear end edge of the terminal connecting portion  21  when the terminal fitting  20  is inserted into an unillustrated housing), the bent-up metal thin wires may interfere with the other member. Furthermore, the outwardly projecting part of the conductor may also interfere with an outside member such as a housing upon being inserted therein. 
     The wire barrel  25  is formed with one or more pressing portions  29  as means for preventing the front end of the conductor  11 , and specifically the metal thin wires of the conductor  11 , from being bent toward the upper side. The pressing portions  29  are formed at or on one or more upper walls  28  of the crimping pieces  27  to be located at a side of the conductor  11  substantially opposite to the bottom wall  26  in the crimped state CS. The pressing portions  29  are formed by hammering after the wire barrel portion  25  is crimped or bent or folded into connection with the conductor  11 . 
     In the crimped state CS, the left and right crimping pieces  27  are laterally symmetric and one pressing portion  29  is formed at each crimping piece  27 . The left and right pressing portions  29  are laterally symmetric. The pressing portions  29  are formed from substantially central positions of the crimping pieces  27  to the front ends of the crimping pieces  27  substantially in forward and backward directions FBD (longitudinal direction of the wire  10 ) and are inclined with respect to the bottom wall  26  to be sloped downward or inward toward the front. This angle of inclination is substantially constant over the entire lengths of the pressing portions  29 . Areas REA of the upper walls  28  of the crimping pieces  27  behind or adjacent to the pressing portions  29  are substantially parallel to the bottom wall  26 . The pressing portions  29  are formed substantially only in central parts of the crimping pieces  27  in a width direction WD. 
     The left and right edges of the upper wall  28  of each crimping piece  27  define folds  30  at the left and right sides of the pressing portion  29 . The folds  30  are such that folded parts face and project upward or outward or away from the conductor  11 . The heights of the upper end edges of the folds  30  are substantially constant. Although the folds  30  are arranged at four positions spaced apart in the width direction WD, the inner two (i.e. standing end edge portions of the both crimping pieces  27 ) folds  30  are held in contact and press each other in the width direction WD. 
     According to this embodiment, the pressing portions  29  are closer to the bottom wall  26  than the rear end areas REA of the crimping pieces  27  are formed at the front ends of the upper walls  28  of the crimping pieces  27  located at the side of the conductor  11  substantially opposite to the bottom wall  26 . The conductor  11  is displaced or deformed toward the bottom wall  26  by the pressing portions  29  at the front ends of the upper walls  28  of the crimping pieces  27  Thus, the height of the front end of the conductor  11 , projecting from the front end of the wire barrel  25 , is suppressed (e.g. as compared to a portion of the conductor  11  corresponding to the upper walls  28 , see e.g.  FIG. 4 ). Therefore, even if the front end portion of the conductor  11  is bent up toward the side opposite to the bottom wall  26 , the height of the bent-up part is suppressed. 
     The pressing portions  29  are inclined to approach the bottom wall  26  toward the front. Thus, the front end portion of the conductor  11  also obliquely projects downward toward the front from the wire barrel  25  to approach the bottom wall  26  as can be seen from  FIG. 4 . Thus, the height of the front end of the conductor  11  can be suppressed more effectively. 
     The pressing portions  29  are formed into recesses or channels by hammering parts of the upper walls  28  of the crimping pieces  27 , excluding the opposite widthwise end portions toward the bottom wall  26 , and the widthwise ends of the front ends of the upper walls  28  define folds  30  projecting away from the bottom wall  26 . The technical significance of this construction is as follows. If the front end portions of the upper walls  28  of the crimping pieces  27  are deformed over the entire widths to approach the bottom wall  26  upon forming the pressing portions  29 , the side walls connecting the upper walls  28  and the bottom wall  26  may be deformed outwardly in the width direction WD by as much as the approach amount of the upper walls  28  toward the bottom wall  26  and the wire barrel portion  25  may be widened. In contrast, in this embodiment, the folds  30  preferably are formed at the opposite widthwise ends of the upper walls  28  and/or only the parts between the folds portions  30  preferably are formed into the pressing portions  29  by being deformed to approach the bottom wall  26 . Thus, it is not necessary to displace the side walls connecting the upper walls  28  and the bottom wall  26  outwardly in the width direction, wherefore the widening of the wire barrel portion  25  can be avoided. 
     The present invention is not limited to the above described and illustrated embodiment. For example, the following embodiments are also included in the technical scope of the present invention. 
     Although the pressing portions have substantially flat inclined surfaces in the above embodiments, they may have curved surfaces. 
     Although the pressing portions are inclined to approach the bottom wall toward the front in the above embodiment, they may be in the form of such steps as to approach the bottom wall. 
     Although the pressing portions are formed by locally recessing the upper walls of the crimping pieces in the width direction in the above embodiment, they may be formed to approach the bottom wall over the entire widths of the upper walls of the crimping pieces. 
     Although the pressing portions are formed after the wire barrel portion is crimped into connection with the conductor in the above embodiment, they may be formed before the conductor is connected by crimping or may be formed simultaneously with the crimping operation.