Abstract:
A terminal assembly includes a wire including a core made of metal and covered with a coating, a terminal including a wire connecting portion connected to an end portion of the wire, a sealing resin sealing the wire connecting portion, and a housing including a through hole with a front opening and a rear opening. The terminal is made of a different kind of metal from the core of the wire. The housing accommodates the terminal in the through hole. The wire connecting portion includes an exposed portion not covered with the sealing resin and unexposed portions covered with the sealing resin. The exposed portion is positioned between the unexposed portions in a front and rear direction, thereby protecting the wire connecting portion from electrolytic corrosion. The exposed portion is obtained after the sealing resin is worn by being rubbed against an inner wall of the through hole.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an anti-corrosion structure for a wire connecting portion. 
     2. Description of the Related Art 
     In recent years, aluminum wires have been used for weight saving and other purposes also in the field of automotive wiring harnesses and the like. An aluminum wire is, for example, structured by covering a core formed by twisting a plurality of aluminum strands with a coating. In the case of forming a wiring harness, the aluminum wire is connected to a wire connecting portion of a terminal. This wire connecting portion is specifically composed of a wire barrel portion to be crimped and connected to an end of the core exposed by stripping the coating at an end of the aluminum wire and an insulation barrel portion to be crimped and connected to an end of the remaining coating. 
     In electrically conductively connecting a wire to a terminal, if a core of the wire and the terminal are made of different types of metals, particularly if moisture is present in a contact part of the both, electrolytic corrosion is known to occur in which the both metals are dissolved in the form of ions into water and corrosion progresses by an electrochemical reaction. Since the terminal is generally made of copper alloy in view of a problem in strength and the like, electrolytic corrosion is certainly a problem if the aluminum wire is used as described above. 
     Accordingly, in a terminal disclosed in Japanese Unexamined Patent Publication No. 2003-297447 below, electrolytic corrosion is prevented by sealing a wire connecting portion by a sealing resin (anticorrosive) made of silicone rubber, chelating agent and the like. However, since such a sealing resin entirely covers the wire connecting portion, the wire connecting portion is formed to be one size larger. Thus, a stepped part is formed on the terminal to avoid the interference of the sealing resin with a housing, into which this terminal is to be mounted, and the interference of the sealing resin and the housing is avoided by this stepped part. 
     However, in the above configuration, the housing is open upward and the wire connecting portion can be arranged while being displaced upward, but the sealing resin interferes with the inner wall of a through hole provided in the housing if the wire connecting portion is displaced upward in the case of accommodating the terminal into the through hole. On the other hand, even if a clearance between the inner wall of the through hole and the sealing resin is enlarged by carving the inner wall of the through hole, there is a limit in terms of securing the strength of the housing. 
     SUMMARY OF INVENTION 
     The present invention was developed based on the situation as described above and an object thereof is to prevent electrolytic corrosion of a wire connecting portion while permitting the interference of a sealing resin and the inner wall of a through hole. 
     The terminal assembly according to the present invention includes a wire including a core made of metal and covered with a coating; a terminal made of a metal different from the core and including a wire connecting portion connected to an end of the wire; a sealing resin sealing the wire connecting portion; and a housing including a through hole with a front opening and a rear opening. The terminal is made of a different kind of metal from the core of the wire. The housing accommodates the terminal in the through hole. The wire connecting portion includes an exposed portion not covered with the sealing resin and unexposed portions covered with the sealing resin. The exposed portion is obtained after the sealing resin is rubbed against an inner wall of the through hole. The exposed portion is arranged in an intermediate part of the wire connecting portion excluding a front end part and a rear end part thereof. 
     If the wire connecting portion is partly exposed at the both front and rear end parts thereof due to the interference of the sealing resin with the inner wall of the through hole, interfaces between the sealing resin and the wire are exposed and water tends to enter the wire connecting portion through these interfaces. In this respect, according to the configuration of the present invention, a part (exposed portion) of the wire connecting portion is exposed in the intermediate part of the wire connecting portion and an interface between the sealing resin and the wire connecting portion is exposed at the exposed portion. However, since the sealing resin and the wire connecting portion are held in close contact with each other, water does not enter the wire connecting portion through this interface. Thus, electrolytic corrosion of the wire connecting portion can be prevented while the interference of the sealing resin and the inner wall of the through hole is permitted. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a section showing a state where a terminal in a first embodiment is inserted in a proper posture in a through hole when viewed sideways. 
         FIG. 2  is a section of the terminal in  FIG. 1  when viewed from above. 
         FIG. 3  is a section showing a state where a stepped part interferes with a sealing resin at an advanced position when viewed sideways. 
         FIG. 4  is a section showing a state where the stepped part is in contact with an exposed portion at the advanced position when viewed sideways. 
         FIG. 5  is a section showing a state where the stepped part interferes with the sealing resin at a retracted position when viewed sideways. 
         FIG. 6  is a section showing a state where the stepped part is in contact with the exposed portion at the retracted position when viewed sideways. 
         FIG. 7  is a section showing the state where the stepped part interferes with the sealing resin at the advanced position when viewed from above. 
         FIG. 8  is a section showing the state where the stepped part is in contact with the exposed portion at the advanced position when viewed from above. 
         FIG. 9  is a section showing the state where the stepped part interferes with the sealing resin at the retracted position when viewed from above. 
         FIG. 10  is a section showing the state where the stepped part is in contact with the exposed portion at the retracted position when viewed from above. 
         FIG. 11  is a section showing a terminal in a second embodiment in a state where a stepped part interferes with a sealing resin when viewed sideways. 
         FIG. 12  is a section showing a state where the stepped part is in contact with an exposed portion when viewed sideways. 
         FIG. 13  is a section showing the state where the stepped part interferes with the sealing resin when viewed from above. 
         FIG. 14  is a section showing the state where the stepped part is in contact with the exposed portion when viewed from above. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     A first embodiment of the present invention is described in detail with reference to  FIGS. 1 to 10 . A terminal  10  in this embodiment is made of copper alloy and includes a terminal connecting portion  20  connectable to a male terminal (see  FIG. 11 ) and a wire connecting portion  30  formed behind this terminal connecting portion  20 . This terminal  10  is inserted and accommodated from behind into a through hole  41  formed to penetrate a housing  40  in forward and backward directions. A locking lance  42  extending forward in a cantilever manner is formed in the through hole  41 . This locking lance  42  is engaged with the terminal  10 , whereby the terminal  10  is held in the through hole  41  so as not to come out backward. 
     The terminal connecting portion  20  is in the form of a rectangular tube which is open forward and backward, and the male terminal is fittable thereinto through a front end opening thereof. Further, a resilient contact piece  21  is formed in the terminal connecting portion  20  by being folded backward from the front edge of the bottom wall of the terminal connecting portion  20 . This resilient contact piece  21  is resiliently deformable in a vertical direction, and resiliently comes into contact with the male terminal fitted into the terminal connecting portion  20 . In this way, the male terminal is sandwiched between the resilient contact piece  21  and the ceiling wall of the terminal connecting portion  20  and the terminal  10  and the male terminal are electrically conductively connected. 
     The terminal connecting portion  20  is formed with a lance hole (not shown) into which a projection (not shown) formed on the locking lance  32  is fitted for a locking purpose. Since the opening of this lance hole is one size larger than the projection, a clearance is formed between the edge of the opening and the projection. Thus, the terminal  10  is permitted to move in forward and backward directions by as much as the clearance. In this way, the terminal  10  is made loosely movable in forward and backward directions between an advanced position (position of the terminal  10  shown in  FIG. 3 ) and a retracted position (position of the terminal  10  shown in  FIG. 5 ). 
     The wire connecting portion  30  is connected to an end of an aluminum wire W formed by covering a core W 1  made of aluminum or aluminum alloy with an insulating coating. On the other hand, the terminal  10  is made of copper alloy. Thus, the connection of the core W 1  of the aluminum wire W and the wire connecting portion  30  is the connection of different types of metals having different ionization tendencies. This wire connecting portion  30  is composed of a wire barrel portion  31  to be crimped and connected to the core W 1  exposed by stripping the coating at an end of the aluminum wire W and an insulation barrel portion  32  to be crimped and connected to the remaining coating after stripping. 
     As shown in  FIG. 7 , the wire barrel portion  31  includes a pair of barrel pieces  31 A in the form of an open barrel and is crimped to pierce into the core W 1  while the both barrel pieces  31 A are wound around the core W 1  from both left and right sides. 
     On the other hand, as shown in  FIGS. 1 and 7 , the insulation barrel portion  32  is formed to be one size larger than the wire barrel portion  31 , wherein particularly a vertical dimension thereof is about twice as large as that of the wire barrel portion  31 . This insulation barrel portion  32  includes a pair of barrel pieces  32 A in the form of an open barrel and is crimped while the both barrel pieces  31 A are wound around the coating from both left and right sides at the end of the aluminum wire W. 
     A barrel accommodating portion  43  for accommodating the both barrel pieces  32 A of the insulation barrel portion  32  is formed in the through hole  41 . The barrel accommodating portion  43  is formed by radially widening a rear end opening side of the through hole  41  and a stepped part  44  is formed at the front end of this enlarged diameter portion  43 A. The stepped part  44  is arranged substantially in the center of the barrel accommodating portion  43  in forward and backward directions and formed over the entire circumference. 
     The wire connecting portion  30  includes a sealing resin  33  sealed by resin such as silicone rubber or chelating agent. The wire barrel portion  31  and the insulation barrel portion  32  are both embedded in a sealed state by the sealing resin  33 . Thus, water does not enter the wire connecting portion  30  and electrolytic corrosion can be prevented even if different types of metals are connected. Further, as shown in  FIGS. 1 and 2 , the sealing resin  33  is not in contact with the inner wall of the through hole  41  in the case of insertion in a proper posture into the through hole  41 . In this case, the inner wall of the through hole  41  and the sealing resin  33  do not slide against each other and the sealing resin  33  is not scraped. 
     However, the sealing resin  33  interferes with the inner wall of the through hole  41  due to loose movements of the terminal  10 A in forward and backward directions between the advanced position and the retracted position and due to vertical and lateral swinging movements of the aluminum wire W. As a result, the sealing resin  33  is gradually scraped due to repeated sliding movements against the inner wall of the through hole  41 . Thus, an exposed portion  34  which is exposed parts of the both barrel pieces  32 A comes to be arranged on outer peripheral surfaces  32 C formed between both front and rear end surfaces  32 F,  32 R of the both barrel pieces  32 A of the insulation barrel portion  32 . 
     Specifically, as shown in  FIG. 3 , the stepped part  44  comes into line contact with the sealing resin  33  and slides against it due to an upward swinging movement of the aluminum wire W at the advanced position. If the sealing resin  33  is scraped by the stepped part  44  at the advanced position, the stepped part  44  comes into contact with the exposed portion  34  arranged on the outer peripheral surfaces  32 C of the both barrel pieces  32 A as shown in  FIG. 4 . Here, although interfaces between the sealing resin  33  and the outer peripheral surfaces  32 C of the both barrel pieces  32 A are exposed at the exposed portion  34 , water does not enter the wire connecting portion  30  through these interfaces since the sealing resin  33  and the outer peripheral surfaces  32 C of the both barrel pieces  32 A are held in close contact at these interfaces. 
     Further, as shown in  FIG. 5 , the stepped part  44  comes into line contact with the sealing resin  33  and slides against it due to an upward swinging movement of the aluminum wire W at the retracted position. If the sealing resin  33  is scraped by the stepped part  44  at the retracted position, the interfaces between the sealing resin  33  and the outer peripheral surfaces  32 C of the both barrel pieces  32 A are exposed at the exposed portion  34  as shown in  FIG. 6 , but water does not enter the wire connecting portion  30  through these interfaces since the sealing resin  33  and the outer peripheral surfaces  32 C of the both barrel pieces  32 A are held in close contact at these interfaces. 
     Similarly,  FIGS. 7 and 8  show a case where the aluminum wire W is laterally swung at the advanced position. The configuration, function and effect of this case are not described since being the same as in the case where the aluminum wire W is swung upwardly. Further,  FIGS. 9 and 10  show a case where the aluminum wire W is laterally swung at the retracted position. The configuration, function and effect of this case are not described since being the same as in the case where the aluminum wire W is swung upwardly. 
     As described above, according to this embodiment, the interference of the stepped part  44  and the sealing resin  33  due to a swinging movement of the aluminum wire W is permitted. However, even if the sealing resin  33  is scraped to expose the exposed portion  34 , the exposed portion  34  is arranged between the front and rear end surfaces  32 F,  32 R of the both barrel pieces  32 A, i.e. on the outer peripheral surfaces  32 C. Thus, the entrance of water into the wire connecting portion  30  through the exposed portion  34  can be avoided. Therefore, electrolytic corrosion of the wire connecting portion  30  can be prevented. Further, when the terminal  10  is inserted in a proper posture into the through hole  41 , the interference of the sealing resin  33  with the barrel accommodating portion  43  can be avoided. Furthermore, since the stepped part  44  comes into line contact with the sealing resin  33 , an exposed area of the exposed portion  34  can be reduced. 
     Second Embodiment 
     Next, a second embodiment of the present invention is described with reference to  FIGS. 11 to 14 . In this embodiment, the terminal of the present invention is applied to a male terminal. A terminal  50  of this embodiment is connectable to a female terminal (see  FIG. 1 ). The terminal  50  includes a tab portion  51  to be fitted into the female terminal. The tab portion  51  is in the form of a flat plate. The other configuration, functions and effects are the same as in the first embodiment and not repeatedly described. 
       FIG. 11  shows a state where a stepped part  62  formed on the inner wall of a through hole  61  of a housing  60  interferes with a sealing resin  53  sealing a wire connecting portion  52  of the terminal  50  with resin due to an upward swinging movement of an aluminum wire W at an advanced position.  FIG. 12  shows a state where the stepped part  62  comes into line contact with an exposed portion  54  exposed on outer peripheral surfaces  52 C of both barrel pieces  52 A forming the wire connecting portion  52  due to sliding movements of the sealing resin  53  and the stepped part  62  against each other. 
       FIG. 13  shows a state where the stepped part  62  interferes with the sealing resin  53  due to a lateral swinging movement of the aluminum wire W at the advanced position.  FIG. 14  shows a state where the stepped part  62  comes into line contact with the exposed portion  54  exposed on the outer peripheral surfaces  52 C of the both barrel pieces  52 A due to sliding movements of the sealing resin  53  and the stepped part  62  against each other. 
     Also in this embodiment, interfaces between the sealing resin  53  and the outer peripheral surfaces  52 C of the both barrel pieces  52 A are exposed at the exposed portion  54 . However, water does not enter the wire connecting portion  52  through these interfaces since the sealing resin  53  and the outer peripheral surfaces  52 C of the both barrel pieces  52 A are held in close contact at these interfaces. Thus, electrolytic corrosion at the wire connecting portion  52  can be prevented. 
     Other Embodiments 
     The present invention is not limited to the above described and illustrated embodiments. For example, the following embodiments are also included in the technical scope of the present invention. 
     Although the stepped part comes into line contact with the outer peripheral surfaces of the both barrel pieces of the insulation barrel portion in the above embodiments, it may come into line contact with the outer peripheral surfaces of the both barrel pieces of the wire barrel portion according to the present invention. 
     Although the insulation barrel portion is in the form of an open barrel including the pair of barrel pieces in the above embodiments, it may be in the form of a closed barrel having a cylindrical shape according to the present invention. 
     Although the stepped part is formed in the barrel accommodating portion for accommodating the insulation barrel portion in the above embodiments, it may be formed in the inner wall of the through hole accommodating the wire barrel portion according to the present invention. 
     Although the sealing resin does not come into contact with the inner wall of the through hole when the terminal is inserted in a proper posture into the through hole in the above embodiments, it may be more or less pressed into the through hole according to the present invention. 
     Although the wire connecting portion is crimped and connected to the core made of aluminum in the above embodiments, soldering may be applied to the core and then the wire connecting portion may be crimped and connected to this soldered core according to the present invention. 
     Although a combination of aluminum and copper alloy is illustrated as a combination of different types of metals in the above embodiments, another combination may be adopted according to the present invention. 
     The wire may have an exposed end portion not covered with the coating and a coating portion covered with the coating. The wire connecting portion may include a wire barrel portion and an insulation barrel portion. The wire barrel portion may be crimped onto the exposed end portion. The insulation barrel portion may include a barrel piece crimped onto the coated portion. The exposed portion of the wire connecting portion may be located at an outer peripheral surface of the barrel piece. The outer peripheral surface may be located between edges of the barrel piece in the front and rear direction. According to such a configuration, an interface between the sealing resin and the outer peripheral surface of the barrel piece is exposed at the exposed portion exposed on the outer peripheral surface of the barrel. However, since the sealing resin and the outer peripheral surface of the barrel piece are held in close contact with each other, water does not enter the wire connecting portion through this interface. 
     The through hole may include a barrel accommodating portion in which the barrel piece is accommodated. The barrel accommodating portion includes an enlarged diameter portion at a position close to the rear opening of the housing and a small diameter portion on a front side of the enlarged diameter portion. The enlarged diameter portion has a larger diameter than the small diameter portion so that a stepped part is provided therebetween. The stepped part is located at a position corresponding to the exposed portion of the wire connecting portion. According to such a configuration, an exposed area of the exposed portion can be reduced since the stepped part comes into line contact with the sealing resin. 
     An inner wall of the barrel accommodating portion may be in non-contact with the sealing resin when the terminal is in an original position in the through hole. According to such a configuration, the interference of the sealing resin with the inner wall of the through hole can be avoided when the terminal is inserted in the proper posture into the through hole. 
     The core of the wire may be made of one of aluminum or aluminum alloy and the terminal may be made of copper alloy. According to such a configuration, the occurrence of electrolytic corrosion can be prevented effectively even in the case of using an aluminum wire having a high possibility of electrolytic corrosion. 
     According to the present invention, it is possible to prevent electrolytic corrosion of a wire connecting portion while permitting the interference of a sealing resin and the inner wall of a through hole.