CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of German Patent Application No. 102018203800.7, filed on Mar. 13, 2018.
FIELD OF THE INVENTION
The present invention relates to a contact pin and, more particularly, to a contact pin for connecting an electrical conductor made of copper or a copper alloy and an electrical conductor made of aluminum or an aluminum alloy.
BACKGROUND
A contact pin is used to connect current conductors, such as a circuit board and a busbar for car batteries. The contact pin can be produced from wires which can be affixed to the circuit board by soldering or have a spring with which the contact pin can be pressed into the circuit board.
Contact pins made of a copper alloy have an appropriate solidity, deformability, and electrical conductivity. It is desirable to use current conductors made of a cheaper material with a lighter weight, such as aluminum or an aluminum alloy. Copper, however, has a much higher electrochemical potential than aluminum and, consequently, contact corrosion occurs when the copper and aluminum come into contact if an electrolyte such as condensed water is present. There is a need for an inexpensive, viable, and corrosion resistant connection between a copper-based current conductor and an aluminum-based current conductor.
SUMMARY
A contact pin for connecting a first electrical conductor made of copper or a copper alloy and a second electrical conductor made of aluminum or an aluminum alloy comprises a plug-in section, a connecting section, and a coating disposed at least on the connecting section. The plug-in section is adapted to couple to the first electrical conductor. The connecting section is adapted to connect to the second electrical conductor. The coating is corrosion-resistant and compatible with aluminum and copper.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example with reference to the accompanying Figures, of which:
FIG. 1 is a side view of a contact pin according to an embodiment;
FIG. 2 is a sectional side view of an arrangement according to an embodiment;
FIG. 3 is a sectional side view of an arrangement according to another embodiment;
FIG. 4 is a sectional side view of an arrangement according to another embodiment;
FIG. 5 is a sectional side view of an arrangement according to another embodiment; and
FIG. 6 is a sectional side view of an arrangement according to another embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENT(S)
Embodiments of the present invention will be described hereinafter in detail with reference to the attached drawings, wherein like reference numerals refer to the like elements. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that the disclosure will convey the concept of the invention to those skilled in the art.
A contact pin 1 according to an embodiment is shown in FIG. 1. The contact pin 1 extends along a longitudinal axis L and comprises a plug-in section 2 for coupling to a first electrical conductor made of copper or a copper alloy and a connecting section 4 for connecting to a second electrical conductor made of aluminum or an aluminum alloy. The connecting section 4 is disposed at a first free end 5 of the contact pin 1 and the plug-in section 2 is disposed at a second free end 5′ of the contact pin 1 opposite the first free end 5 along the longitudinal axis L.
The plug-in section 2, as shown in FIG. 1, is formed by a radially elastic resilient section 6 which enables elastic pressing into a receptacle of the first electrical conductor made of copper or a copper alloy. The resilient section 6 is broadened outwards substantially perpendicular to the longitudinal axis L and is elastically deformable inwards substantially perpendicular to the longitudinal axis L.
The connecting section 4, as shown in FIG. 1, is configured to be peg-shaped and is adapted to couple to an aluminum-based electrical conductor. The connecting section 4 extends along the longitudinal axis L up to the plug-in section 2 and has a constant outer shape 7 along the longitudinal axis L.
The contact pin 1 is formed from copper and/or a copper alloy. The elastic resilient section 6 in particular is made of a copper alloy, in order to enable elastic deformability for the pressing-in into the first electrical conductor made of copper or a copper alloy. In an embodiment, the resilient section 6 has a different material composition than a material composition of the rest of the contact pin 1.
As shown in FIG. 1, at least the connecting section 4 is coated with a coating 8 that is corrosion-resistant for aluminum and copper. The coating 8 prevents contact corrosion between the aluminum of the electrical conductor and the copper of the contact pin. Since the copper has a much higher electrochemical potential than aluminum, contact corrosion occurs when the two substances come into contact, if an electrolyte such as condensed water is present. The electrochemical potential of the coating 8 lies between the electrochemical potential of copper and of aluminum.
In an embodiment, the coating 8 is single-layered and consists of a tin-zinc alloy, with the percentage by weight of zinc being between approximately 5% and approximately 75%, and in an embodiment, is 20%. The coating 8 is galvanically deposited onto the connecting section 4 and is between approximately 0.5 and approximately 5 μm thick. In the embodiment shown in FIG. 1, the coating 8 that is corrosion-resistant for aluminum and copper is applied only on the connecting section 4. In another embodiment, the contact pin 1 can be completely coated with the corrosion-resistant coating 8. In an embodiment, the plug-in section 2 can be coated with a coating that is different from the coating 8. The plug-in section 2 can be tin-coated, for example, in order to guarantee a corrosion-resistant connection to the copper-based electrical conductor.
As shown in FIG. 2, an arrangement 10 using the contact pin 1 further comprises a first electrical conductor 14 made of copper or a copper alloy and a second electrical conductor 20 made of aluminum or an aluminum alloy. In an embodiment, the first electrical conductor 14 is a circuit board and the second electrical conductor 20 is a busbar. In an embodiment, the second electrical conductor 20 is produced by deep-drawing, extrusion, or stamping.
The contact pin 1, as shown in FIG. 2, is plugged with the plug-in section 2 into a receptacle 12 of the first electrical conductor 14. The receptacle 12 penetrates the first electrical conductor 14 along the longitudinal axis L. A width of the resilient section 6, in a non-plugged-in state, is larger than a width of the receptacle 12. When pressed-in, the resilient section 6 is radially deformed inwards perpendicular to the longitudinal axis L, so that high driving forces arise between the resilient section 6 and the receptacle 12. As a result, there arises a gas-tight zone and a low-impedance electrical connection between the contact pin 1 and the first electrical conductor 14.
The peg-shaped connecting section 4, as shown in FIG. 2, is introduced in a coupling section 16, which has the form of a socket 18, of the second electrical conductor 20. The connecting section 4 and the coupling section 16 are configured to be complementary so that a good fit and a good hold can be achieved between the two. The connecting section 4 has a constant outer shape 7 along the longitudinal axis L, while the socket 18 has an aperture 22 which extends along the longitudinal axis and which has a constant inner width 24 along the longitudinal axis. In an embodiment, the connecting section 4 and the coupling section 16 each have a cross-section that is constant along a plug-in direction E. In an embodiment, an inner cross-section of the coupling section 16 and an outer shape of the connecting section 4 are rotationally symmetrical. As a result, the plugging-together of the contact pin 1 and the second electrical conductor 20 is facilitated.
By virtue of the coating 8, a corrosion of the aluminum of the second electrical conductor 20 and of the copper of the contact pin 1 is prevented. As a result, a simple connection of the first electrical conductor 14 made of copper or a copper alloy and the second electrical conductor 20 made of aluminum or an aluminum alloy is possible with the contact pin 1. The coating 8 is optimized for a connection to the aluminum and to the copper.
As shown in FIG. 2, the connecting section 4 is introduced in a plug-in direction E, which runs parallel to the longitudinal axis L, into the aperture 22 of the second electrical conductor 20. This can be carried out by the application of force so that the contact pin 1 and the second electrical conductor 20 are pressed together. In order to further strengthen the cohesion, the coupling section 16 can be welded, soldered and/or crimped to the connecting section 4.
In various embodiments, the second electrical conductor 20 can connect to a current conductor, such as a busbar or an accumulator, for example. Depending on the application, the length of the second electrical conductor 20 can be adapted. The second electrical conductor 20 can, for example, have a closed pin-shaped free end which faces away from the coupling section 16 and which can be connected to the current conductor by pressing, soldering, or by some other method. Furthermore, the second electrical conductor 20 can be outwardly insulated by an electrically non-conductive casing in order to avoid short-circuiting.
As shown in FIG. 2, the second electrical conductor 20 has at its outer surface 26 a clamping zone 28 which is formed by an indentation 30. Through an action of mechanical force onto this clamping zone 28, the contact pin 1 and the second electrical 20 are squeezed together.
The electrical conductors 14, 20, as shown in FIG. 2, are spaced apart from one another in plug-in direction E. In order to avoid contact between the electrical conductors 14, 20, the arrangement 10 has a polymer-containing sealing body 31 between the two electrical conductors 14, 20. The sealing body 31 can be formed by capillary casting. The sealing body 31 prevents dirt and condensed water from ending up between the electrical conductors 14, 20. In an embodiment, the sealing body 31 is a sealing ring or a potting between the electrical conductors 14, 20 and is made of an insulating polymer.
In another embodiment of an arrangement 10 shown in FIG. 3, the connecting section 4 of the contact pin 1 has at least one shoulder 32 that protrudes laterally relative to the longitudinal axis L. As a result, when the second electrical conductor 20 and the contact pin 1 are squeezed together, at least one undercut 34 is formed in order to strengthen the connection between the contact pin 1 and the second electrical conductor 20 in a form-fitting manner.
In the unsqueezed state 36, shown in FIG. 3, the socket 18 has an aperture 22 with an unvarying inner width 24. The outer shape 7 of the connecting section 4 has, at its side facing away from the first electrical conductor 14, the shoulder 32 which protrudes laterally perpendicular to the longitudinal axis L and which can have a blade-shaped surface structure in order to support an ingress into the socket 18. The breadth of the shoulder 32 is designed to be complementary to the aperture 22 so that the connecting section 4 can be easily introduced into the socket 18. During the squeezing-together, the aperture 22 narrows until the inner surface of the aperture 22 lies against the outer shape 7 of the connecting section 4. A friction-locking connection arises and a form-fitting connection arises due to the shoulder 32 located in the formed undercut 34. The squeezed state 38 is shown with a solid line in FIG. 3 and the unsqueezed state 36 is depicted with a dashed line.
In an arrangement 10 according to another embodiment, as shown in FIG. 4, the contact pin 1 has a second radially elastic resilient section 40 which forms the connecting section 4. The coating 8 is applied in three layers 42, 44, 46. The first layer 42 consists of nickel and is applied on the outer surface of the connecting section 4. The second layer 44 consists of zinc and the third layer 46 consists of tin.
The nickel from the first layer 42 connects to the copper of the contact pin 1 and serves as a diffusion-blocking layer. The first layer 42 prevents an interdiffusion between the copper atoms and the atoms of the coating 8 or aluminum of the second electrical conductor 20. The formation of intermetallic Cu—Al compounds with high electrical resistances is inhibited by the diffusion-blocking layer. The tin from the third layer 46 contacts the aluminum of the second electrical conductor 20. As a result, there occurs at least a partial interdiffusion between the atoms of the two materials, and the connection between the second electrical conductor 20 and the contact pin 1 is strengthened.
The second resilient section 40 is plugged into the aperture 22 of the second electrical conductor 20, as shown in FIG. 4. Due to the press-connection between the contact pin 1 and the second electrical conductor 20, a clamping zone 28, as shown in FIG. 2, is not required. The second electrical conductor 20 therefore has a constant breadth.
An arrangement 10 according to another embodiment is shown in FIG. 5. The first free end 5 of the connecting section 4 is substantially bent back by 180° and forms an aperture 22 between the free end 5 of the connecting section 4 and an end of the connecting section 4 adjacent the plug-in section 2. The connecting section 4 is deformed in a hook-shaped manner in a non-clamped state 48. A peg-shaped coupling section 16 of the second electrical conductor 20 can be plugged through into the aperture 22 so that the coupling section 16 is arranged substantially parallel to the first electrical conductor 14. In order to strengthen the connection between the connecting section 4 and the coupling section 16, the free end 5, in a clamped state 50, is bent inwards to that end of the connecting section 4 which is adjacent the plug-in section 2. In the clamped state 50, the aluminum-based second electrical conductor 20 is connected to the contact pin 1 in a friction-locking manner. The embodiment of FIG. 5 makes it possible to contact a current conductor parallel to the plane of the first electrical conductor 14 and is advantageous when there is limited space.
An arrangement 10 according to another embodiment is shown in FIG. 6. The contact pin 1, as shown in the embodiment of FIG. 4, has a first radially elastic resilient section 6 for elastically pressing into the receptacle 12 of the first electrical conductor 14 and a second radially elastic resilient section 40 for elastically pressing into an aperture 22 of the second electrical conductor 20. The electrical conductors 14, 20 are configured here as flat conductors or busbars. The receptacle 12 penetrates the copper-based first electrical conductor 14 along the longitudinal axis L of the contact pin 1. The contact pin 1 is plugged into the receptacle 12 against the plug-in direction E by its plug-in section 2. The second radially elastic resilient section 40 forms the connecting section 4 and is plugged into the aperture 22 which penetrates the second electrical conductor 20 along the plug-in direction E.
The connecting section 4, as shown in FIG. 6, has a three-layered coating 8. The first layer 42 consists of nickel and is applied directly onto the connecting section 4. The second layer 44 consists of zinc and the third layer 46 consists of tin. The third layer 46 of the contact pin 1 points outwards and thus contacts the aluminum of the second electrical conductor 20.
A width of the resilient sections 40, 6, in the non-plugged-in state, is larger than a width of the aperture 22 or receptacle 12. When plugged into the aperture 22 or receptacle 12, the resilient sections 40, 6 deform radially inwards perpendicular to the longitudinal axis L, so that high driving forces come into being between the resilient sections 6, 40 and the receptacle 12 or aperture 22. This leads to a gas-tight zone and a low-impedance electrical connection between the contact pin 1 and the electrical conductors 14, 20.
In an embodiment, the coating 8 can be up to 5 μm thick, and the individual layers 42, 44, 46 can have different thickness. In another embodiment, the individual layers 42, 44, 46 can have a same thickness. As a result, the coating 8, depending on the use, can be optimized for the connection between the first electrical conductor 14 and the second electrical conductor 20. With the coating 8, contact corrosion can be prevented from occurring between the copper of the contact pin 1 and the aluminum of the second electrical conductor aluminum alloy 20. With the arrangement 10 shown in FIG. 6, it is possible to create a simple connection between two flat conductors or busbars, with one flat conductor consisting of copper or a copper alloy and the other flat conductor consisting of aluminum or an aluminum alloy.
Patent Grant
11121495
