Patent Application
20190036238
This application claims priority from Japanese Patent Application No. 2017-145541 filed on Jul. 27, 2017, the entire contents of which are incorporated herein by reference.
The present invention relates to an electric wire with a terminal which includes an electric wire and a terminal fitting.
For example, in a wire harness routed in a vehicle, an electric wire with a terminal in which a terminal fitting made of copper or a copper alloy is crimp-connected with the electric wire (hereinafter, referred to as an “aluminum electric wire”.) including a core wire made of aluminum or an aluminum alloy is used for reduction in weight. Incidentally, in the electric wire with a terminal, there is a concern that water adhering between the core wire of the electric wire and the terminal fitting which are dissimilar metals becomes electrolyte so that galvanic corrosion (dissimilar-metal contact corrosion) occurs. Incidentally, as is well known, the galvanic corrosion occurs due to the difference of the standard electrode potential between the dissimilar metals, and as the difference is larger, the galvanic corrosion occurs more easily.
For this reason, a plated layer or an insulation film is formed in a surface of the crimp portion of the terminal fitting to the electric wire, so as to prevent the galvanic corrosion (see, for example, the patent document 1: JP-A-2012-94340, the patent document 2: JP-B-5196535, the patent document 3: JP-A-2012-69449, the patent document 4: JP-A-2013-149598, the patent document 5: JP-A-2013-127907, the patent document 6: JP-A-2013-218866, and the patent document 7: JP-A-2013-182861).
A plated layer containing tin is exemplified as the plated layer provided in the terminal fitting to prevent the galvanic corrosion between the core wire of the aluminum electric wire and the terminal fitting. One of the reasons is that the difference (a difference in a plated state) of the standard electrode potential between the tin configuring the plated layer and the aluminum alloy or the aluminum is smaller than the difference (a difference in a non-plated state) of the standard electrode potential between the copper or the copper alloy which is a general material of the terminal fitting and the aluminum or the aluminum alloy. In other words, compared to the former one (non-plated state), in the latter one (plated state), the galvanic corrosion can be prevented by an amount corresponding to the smallness of the difference of the standard electrode potential.
Incidentally, the standard electrode potential is a parameter regarding to an ionization tendency (ease of corrosion) of a material, and the ionization tendency is larger and the corrosion occurs more easily as the standard electrode potential is smaller. For example, the standard electrode potential can be defined as an electromotive force in a standard state of a battery obtained by combining the electrode of the material and a standard hydrogen electrode. For example, the standard electrode potential of the aluminum is appropriately −1.67 V, the standard electrode potential of the tin is appropriately −0.14 V, and the standard electrode potential of the copper is appropriately 0.52 V. The standard electrode potential of the aluminum alloy is different according to the composition, but generally is smaller than the above-described standard electrode potential of the tin and the copper. Similarly, the standard electrode potential of the copper alloy is different according to the composition, but generally is larger than the above-described standard electrode potential of the aluminum and the aluminum alloy.
Incidentally, in a case where the plated layer containing tin is provided in the terminal fitting, when a layer (for example, a copper foundation layer and a copper base material of the terminal fitting) containing copper or a copper alloy contacts with the plated layer, a copper-tin alloy may be formed between the layer containing copper or a copper alloy and the plated layer. In a case where the copper-tin alloy is grown to be exposed in the surface of the plated layer, the exposed copper-tin alloy contacts with the core wire of the aluminum electric wire. Herein, the standard electrode potential of the copper-tin alloy is different according to the composition, but generally is larger than the standard electrode potential of the tin (original plated layer). In other words, the difference (the copper-tin alloy is exposed) of the standard electrode potential between the copper-tin alloy and the core wire material of the aluminum electric wire is larger than the difference (the copper-tin alloy is not exposed) of the standard electrode potential between the tin and the core wire material. Accordingly, in a case where the copper-tin alloy is exposed in the surface of the plated layer as above, the galvanic corrosion occurs more easily compared to a case where there is no exposure. Such corrosion is desired to be prevented.
One or more embodiments provide an electric wire with a terminal which is excellent in corrosion resistance by preventing corrosion of a core wire of an aluminum electric wire.
In order to achieve the object described above, an electric wire with a terminal according to the invention is characterized by (1) to (4) below.
In an aspect (1), one or more embodiments provide an electric wire with a terminal including an electric wire including a core wire made of aluminum or an aluminum alloy and a terminal fitting including a barrel part crimp-connected with the core wire and a contact part connected with a counterpart terminal. The barrel part includes a first layer containing tin and a second layer containing copper or a copper alloy in this lamination order from a side closer to the core wire. The first layer is formed so that a distance between a surface of the first layer on a core wire side and a surface of the second layer on the core wire side in a laminating direction is larger than a thickness of a copper-tin alloy area formed by the tin contained in the first layer and the copper contained in the second layer in the laminating direction.
In an aspect (2), the contact part includes a third layer containing tin and the second layer in this lamination order from a side closer to the counterpart terminal. The third layer is formed so that a distance between a surface of the third layer on a counterpart terminal side and a surface of the second layer on the counterpart terminal side in the laminating direction is smaller than the distance between the surface of the first layer on the core wire side and the surface of the second layer on the core wire side in the laminating direction.
In an aspect (3), the electric wire with the terminal further includes a connection part which connects the barrel part and the contact part. The connection part includes the first layer and the second layer similarly to the lamination order of the barrel part.
In an aspect (4), an outer circumferential surface of the core wire is covered with the barrel part to be separated from the outside. The terminal fitting is connected with the core wire so that a tip end of the core wire is exposed from the barrel part and extends to the connection part.
According to the aspect (1), the barrel part crimp-connected with the core wire of the aluminum electric wire includes the first layer containing tin and the second layer containing copper or a copper alloy in an order closer to the core wire. Further, as for the layer structure in the laminating direction, the first layer is formed such that the distance between the surface of the first layer on the core wire side and the surface of the second layer on the core wire side in the laminating direction is larger than the thickness of the copper-tin alloy area, which is formed by the tin contained in the first layer and the copper contained in the second layer, in the laminating direction. For this reason, the copper-tin alloy is not exposed in the surface of the first layer, and the galvanic corrosion between the copper-tin alloy and the core wire of the aluminum electric wire can be prevented.
Therefore, the electric wire with a terminal having this configuration can prevent the corrosion of the core wire of the aluminum electric wire and is excellent in the corrosion resistance compared to a case where the first layer does not have the above-described configuration and the copper-tin alloy is exposed on the surface of the first layer.
According to the aspect (2), the contact part connected with the counterpart terminal includes the third layer containing tin. However, the third layer is formed such that the distance between the surface of the third layer on the counterpart terminal side and the surface of the second layer on the counterpart terminal side in the laminating direction is smaller than the distance of the first layer. In other words, the thickness of the third layer in the laminating direction is smaller than the thickness of the first layer in the laminating direction. The reason is that when the thickness of the plated layer provided in the contact part is excessively large, a contact pressure between the counterpart terminal and the contact part may be enlarged so that both terminals are hardly connected. Accordingly, the electric wire with a terminal having this configuration can achieve both a connectivity between the terminal fitting (connection part) and the counterpart terminal and the prevention of the corrosion of the aluminum electric wire in the terminal fitting (barrel part) as described above.
According to the aspect (3), in the connection part which connects the barrel part and the contact part, the first layer and the second layer are provided similarly to the barrel part. Therefore, for example, even in a case where the terminal fitting is attached such that the tip end of the core wire of the aluminum electric wire is exposed from the barrel part to extend to the connection part (see following description), the corrosion of the core wire exposed from the barrel part can be prevented by preventing the exposure of the copper-tin alloy similarly to the above.
According to the aspect (4), the tip end of the core wire of the aluminum electric wire is exposed from the barrel part to extend to the connection part. For this reason, even when that the core wire is corroded, the tip end which is exposed from the barrel part is corroded more preferentially than the portion covered with the barrel part. At that time, the corrosion of the portion covered with the barrel part is delayed by the amount of the core wire exposed from the barrel part. In other words, the core wire exposed from the barrel part is corroded sacrificially, so that it can be prevented that the contact place (the core wire inside the barrel part), which is important in functioning as the electric wire with a terminal, between the barrel part and the core wire is corroded. Incidentally, the improvement of the corrosion resistance of the electric wire with a terminal can contribute to the miniaturization of the terminal and the thinning of the core wire.
According to one or more embodiments, the electric wire with a terminal can be provided which is excellent in the corrosion resistance by preventing the corrosion of the core wire of the aluminum electric wire.
By reading through the following described a mode to carry out the invention (hereinafter, referred to as an “embodiment”) with reference to the accompanying drawings, details of the invention will be further clarified.
Hereinafter, an embodiment according to the invention will be described with reference to the drawing.
As illustrated in
The electric wire 10 is an insulated electric wire including the core wires 11 and a sheath 12 which covers the core wire 11 and is made of a resin. The core wire 11 is made of aluminum or an aluminum alloy, and is formed by twisting a plurality of strands. When the core wire 11 of the electric wire 10 is made of aluminum or an aluminum alloy, the terminal fitting 20 is reduced in weight, and the wire harness including the terminal fitting 20 is also reduced in weight. The terminal fitting 20 reduced in weight is properly used particularly in a vehicle, which uses frequently the wire harness, such as an electric automobile or a hybrid automobile.
The terminal fitting 20 includes a contact part 31 to be connected with a counterpart terminal on a front side, and a barrel part 41 to be connected with the core wire 11 of the electric wire 10 on a rear side. The contact part 31 and the barrel part 41 are connected with each other by a connection part 35.
After punched by the press processing, as illustrated in
As illustrated in
The barrel part 41 is performed to the above-described surface treatment, and as illustrated in
When the tin-plated layer 21d has such a thickness, it is prevented that the copper-tin alloy area 21e is exposed in the surface of the tin-plated layer 21d. Herein, the standard electrode potential of the copper-tin alloy is different according to the composition, but generally is larger than the standard electrode potential of the tin (original tin-plated layer 21d). That is, the difference (the copper-tin alloy area 21e is exposed) of the standard electrode potential between the copper-tin alloy and the aluminum material of the core wire 11 is larger than the difference (the copper-tin alloy area 21e is not exposed) of the standard electrode potential between the tin and the aluminum material of the core wire 11. Accordingly, compare to a case where there is an exposure, the galvanic corrosion between the core wire 11 of the electric wire 10 and the copper-tin alloy area 21e is prevented by preventing the exposure of the copper-tin alloy area 21e.
On the other hand, as illustrated in
As described above, in the terminal fitting 20 of this embodiment, the surface treatment performed on the barrel part 41 and the surface treatment performed on the contact part 31 are different from each other in terms of the thickness of the tin-plated layer 21d in the laminating direction.
The connection part 35 is also performed to the surface treatment similarly to the barrel part 41, and the connection part 35 has a sectional structure similar to
After the surface treatment is performed as described above, the contact part 31 is formed in a cylindrical shape having an open tip end part as illustrated in
The barrel part 41 is electrically connected to the end part of the electric wire 10 to be crimped. The barrel part 41 includes a pair of crimp pieces 42. In each of the crimp pieces 42, the front side is formed a conductor crimp part 45, and the rear side is formed a sheath crimp part 46. In addition, in the crimp piece 42, a portion between the conductor crimp part 45 and the sheath crimp part 46 is formed a connecting part 47. In the barrel part 41, an upper surface as one surface is formed a placing surface 41a on which the end part of the electric wire 10 is arranged. The crimp piece 42 is bent to enclose the end part of the electric wire 10 in a state where the end part of the electric wire 10 is arranged in the placing surface 41a. Therefore, in the crimp pieces 42, the respective end parts are caulked to be overlapped with each other and are crimped to the end part of the electric wire 10.
When the barrel part 41 is crimped to the end part of the electric wire 10, as illustrated in
A following method is exemplified as a method that allows the tip end 11a of the core wire 11 to be exposed from the barrel part 41. For example, a method is exemplified in which the tip end 11a of the core wire 11 is arranged in the area between the barrel part 41 and the contact part 31 before the barrel part 41 is crimped to the core wire 11, and then the barrel part 41 is crimped to the core wire 11. Further, for example, a method is exemplified in which the tip end of the core wire 11 is positioned to be covered with the barrel part 41 before the barrel part 41 is crimped to the core wire 11, and in the process to crimp the barrel part 41 to the core wire 11, the core wire 11 is deformed to be exposed from the barrel part 41 (extrudes from the barrel part 41). Among these methods, in the latter method, the core wire 11 and the barrel part 41 slide in a close contact state when the core wire 11 extrudes from the barrel part 41. Thus, there is a merit that the electrical connection between the core wire 11 and the barrel part 41 can be made more firmly.
A pressure protrusion part 51 (protrusion part), a front protrusion part 52 (protrusion part), and a rear protrusion part 53 (protrusion part) are formed in the barrel part 41. The pressure protrusion part 51 is provided substantially in the center of the barrel part 41 in a width direction, and is formed along a longitudinal direction of the electric wire 10. The front protrusion part 52 is provided on the front side of the barrel part 41, and the rear protrusion part 53 is provided on the rear side of the barrel part 41. Both the front protrusion part 52 and the rear protrusion part 53 are formed along the width direction of the barrel part 41. All of the pressure protrusion part 51, the front protrusion part 52, and the rear protrusion part 53 protrude to the inside which is the electric wire 10 side from the placing surface 41a on which the end part of the electric wire 10 is placed. Further, in the barrel part 41, a serration 55 including a plurality of hole parts is formed in the inner surface which is the placing surface 41a.
When the crimp piece 42 of the barrel part 41 is crimped to the end part of the electric wire 10, as illustrated in
When the crimp piece 42 is crimped to the electric wire 10, the serration 55 formed in the placing surface 41a of the barrel part 41 bites into the core wire 11. Therefore, an oxide film of the surface of the core wire 11 is removed to obtain an excellent conductive state between the electric wire 10 and the terminal fitting 20.
Herein, as illustrated in
As described above, in the electric wire with a terminal 1 according to this embodiment, the barrel part 41 crimp-connected with the core wire 11 of the electric wire 10 includes the tin-plated layer 21d and the foundation layer 21c of the copper in an order closer to the core wire 11. Further, as for the layer structure in the laminating direction, the tin-plated layer 21d is formed such that the distance between the surface of the tin-plated layer 21d on the core wire 11 side and the surface of the foundation layer 21c on the core wire 11 side in the laminating direction is larger than the thickness of the copper-tin alloy area 21e, which is formed by the tin contained in the tin-plated layer 21d and the copper contained in the foundation layer 21c, in the laminating direction. For this reason, the copper-tin alloy is not exposed in the surface of the tin-plated layer 21d, and the galvanic corrosion between the copper-tin alloy and the core wire 11 can be prevented.
The contact part 31 connected with the counterpart terminal includes the tin-plated layer 21d of which the thickness in the laminating direction is smaller than that of the tin-plated layer 21d in the barrel part 41. Therefore, it can be prevented that the contact pressure of the counterpart terminal and the contact part 31 of the terminal fitting 20 is excessively high, and the counterpart terminal is hardly connected with the terminal fitting 20.
The tin-plated layer 21d similar to the barrel part 41 is provided in the connection part 35 which connects the barrel part 41 and the contact part 31. Therefore, even in a case where the terminal fitting 20 is attached such that the tip end 11a of the core wire 11 is exposed from the barrel part 41 to extend to the connection part 35, the galvanic corrosion of the core wire 11 can be prevented similarly to the above.
The tip end 11a of the core wire 11 is exposed from the barrel part 41 to extend to the connection part 35. Thus, when the above-described galvanic corrosion occurs so that the core wire 11 is corroded, the tip end 11a which is exposed from the barrel part 41 is corroded more preferentially than the portion covered with the barrel part 41. Further, the corrosion progresses gradually from the tip end 11a of the core wire 11. Thus, the corrosion of the portion covered with the barrel part 41 is delayed by the length of the core wire 11 exposed from the barrel part 41. In other words, the core wire 11 exposed from the barrel part 41 is corroded sacrificially, so that it can be prevented that the contact place (the core wire 11 inside the barrel part 41), which is important in functioning as the electric wire with a terminal 1, between the barrel part 41 and the core wire 11 is corroded.
Incidentally, the invention is not limited to the above-described embodiment, and various modifications may be adopted within the scope of the invention. For example, the invention is not limited to the above-described embodiment, and may be modified or improved appropriately. In addition, material, shape, size, number, location or the like of each component in the above-described embodiments are arbitrary and not limited as long as they can attain the invention.
For example, various protrusion parts (the pressure protrusion part 51, the front protrusion part 52, and the rear protrusion part 53) are formed in the barrel part 41 in the embodiment. However, the terminal fitting according to the invention may not be such a protrusion part. The same applies to the serration 55.
In the barrel part 41 in the above-described embodiment, the nickel layer 21b and the foundation layer 21c are held between the base material layer 21a and the tin-plated layer 21d. However, the tin-plated layer 21d may be directly provided in the base material layer 21a.
Herein, the features of the above-described embodiments of an electric wire with a terminal according to the invention will be simply summarized as the following [1] to [4].
[1] An electric wire with a terminal (1) comprising:
an electric wire (10) including a core wire (11) made of aluminum or an aluminum alloy; and
a terminal fitting (20) including a barrel part (41) crimp-connected with the core wire and a contact part (31) connected with a counterpart terminal,
wherein the barrel part includes a first layer (21d) containing tin and a second layer (21c) containing copper or a copper alloy in this lamination order from a side closer to the core wire, and
wherein the first layer is formed so that a distance (a) between a surface of the first layer on the core wire side and a surface of the second layer on a core wire side in a laminating direction is larger than a thickness (b) of a copper-tin alloy area (21e) formed by the tin contained in the first layer and the copper contained in the second layer in the laminating direction.
[2] The electric wire with the terminal according to [1],
wherein the contact part (31) includes a third layer (21d) containing tin and the second layer in this lamination order from a side closer to the counterpart terminal, and
wherein the third layer is formed so that a distance (c) between a surface of the third layer on a counterpart terminal side and a surface of the second layer on the counterpart terminal side in the laminating direction is smaller than the distance (a) between the surface of the first layer on the core wire side and the surface of the second layer on the core wire side in the laminating direction.
[3] The electric wire with the terminal according to [1] or [2], further comprising:
a connection part (35) which connects the barrel part and the contact part,
wherein the connection part includes the first layer and the second layer similarly to the lamination order of the barrel part.
[4] The electric wire with the terminal according to [3],
wherein an outer circumferential surface of the core wire is covered with the barrel part (41) to be separated from an outside, and
wherein the terminal fitting is connected with the core wire so that a tip end (11a) of the core wire is exposed from the barrel part and extends to the connection part (35).
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-145541 | Jul 2017 | JP | national |
