EP1759439B1 - Electrical contact connection and method for creating one such contact connection - Google Patents

Abstract

In order to make it possible to produce a secure and permanent contact connection between an electrical conductor made from a soft material, in particular an aluminum conductor, and a contact element made from a harder material, the conductor is encapsulated at least partially in a contact region by an electrically conductive material. The electrically conductive material is harder than the soft material of the conductor. The electrically conductive material is applied with the aid of a thermal spraying process, with the result that there is a pressure-free electrical connection between the soft material and the sprayed-on material. Electrical contact is made with the contact element indirectly via the sprayed-on material. The thermal encapsulation by the spraying in the contact region makes it possible for a reliable electrical contact to be made even in the case of soft materials having a tendency towards cold flow.

Description

The invention relates to an electrical contact connection between an electrical conductor made of a soft material, in particular an aluminum conductor, and a contact element according to the preamble of claim 1. The invention further relates to a method for forming such a contact connection according to the preamble of claim 8.

Such a contact connection is known from GB 755 272 A refer to. In this known contact connection, an aluminum conductor is inserted with its end in an aluminum sleeve, and inserted together with this in a crimp sleeve of a contact element and connected thereto by crimping.

In an electrical contact connection between a soft material, such as aluminum, magnesium or alloys thereof, with a harder material has the problem that the soft material evades the pressure under pressure during a time, so that the electrical contact connection is weakened and can come to contact problems. This property of soft materials to yield under pressure is commonly referred to as material flow or cold flow.

Due to this cold flow, there are considerable problems to ensure long-term stable, secure contact connections between a soft and a hard material.

The present invention has for its object to provide a secure electrical contact connection between a soft, prone to cold flow material and another contact element.

The object is achieved by an electrical contact connection with the features of claim 1. Thereafter, it is provided that an electrical conductor of a soft, prone to cold flow material in its contact region at least partially by means of a spraying process with a compared to the soft material of the conductor harder, electrically conductive material is encapsulated. The electrical contact with a contact element via the sprayed material.

The spraying of a harder material onto the electrical conductor has the decisive advantage that an intimate and pressure-free connection between the soft material of the conductor and the harder sprayed-on material is formed by the injection method. By spraying, at least some of the sprayed hard particles deposited in the near-surface region in or on the soft material, so that a cohesive and thus permanent connection between the soft and the hard material is formed. The electrical connection to the contact element via the sprayed hard material, so that there is a Hart-Hartverbindung between two not or only slightly prone to cold flow materials. The electrical contacting of the conductor with the contact element therefore takes place only indirectly via the sprayed-on material.

In particular, a thermal spraying process, such as hot gas spraying or, preferably, flame spraying, is suitable as the spraying process. Alternatively, the material may also be conveyed via a cold process, e.g. be applied with the so-called cold gas spraying. In contrast to the thermal spraying process, the particles to be scrubbed are not melted or fused. For the desired intimate connection and good adhesion between the soft material and the sprayed-on material, it is crucial that thermal and / or kinetic energy of the sprayed-on particles permanently anchor them in the soft material.

The electrical conductor used is preferably an aluminum conductor, in particular consisting of a plurality of individual conductors or strands. Soft material is to be understood here in particular as conducting materials from the elements of the third row of the Periodic Table, in particular aluminum, aluminum alloys or magnesium alloys. Hard material is understood to mean, in particular, conductive materials of elements of the fourth row of the periodic table, for example copper, nickel, iron, chromium and alloys for this purpose, in particular chromium-nickel alloys.

According to an expedient embodiment, the conductor in the contact region is completely surrounded by a jacket of the type of a tube made of the harder material. The tube is in this case designed in particular as a hard metal tube and has a high inherent rigidity and dimensional stability, so that it has a high mechanical resistance. Conveniently, in this case, the tube is formed of a nickel-chromium-nickel alloy, which has particularly good electrical and mechanical properties.

Conveniently, the contact connection between the sprayed material and the contact element via a mechanical pressure or clamping connection. The contact connection is formed in particular via a clamping or crimp contact. Since there is the connection between two hard materials, there is little or no risk of cold flow, so that even with a pressure-sensitive mechanical connection a permanently secure electrical contact is ensured. In particular, in connection with the dimensionally stable and intrinsically stiff designed in the manner of a tube jacket secure contact is guaranteed.

Conveniently, the conductor has at its end an enlarged cross-sectional area of contact compared to the conductor cross-sectional area, onto which the conductive material is sprayed. The conductor is preferably bevelled end side. The front end of the conductor is therefore encapsulated with the conductive material, which preferably forms a kind of end cap. By increasing the contact cross-sectional area compared to the normal cross-sectional area, the largest possible effective contact area for the current transport is achieved.

This is particularly advantageous in DC applications or in applications with alternating current at low frequency, since in these cases the so-called skin effect does not occur or hardly occurs and a current is transported over the entire conductor cross-sectional area. A contact connection that does not involve the entire cross-sectional area of the conductor would result in a very high contact resistance. In contrast to this, current transport takes place only near the surface, especially in the case of high-frequency alternating currents Exterior, the "skin" of the ladder, so that the ladder core does not contribute to power transport. Since the injection molding of the material is not necessarily a 100% areal connection between the soft material and the sprayed hard material is formed by increasing the contact cross-sectional area of the effective contact surface, ie the area at which an actual contact between the sprayed material and the soft material, for example, increases and amounts to 100% of the normal conductor cross-sectional area. Thus, the contact resistance is kept as low as possible. Under normal conductor cross-sectional area is understood here as the cross-sectional area, which is formed by a vertical section to the conductor longitudinal propagation.

The enlargement of the contact cross-sectional area by the chamfer is particularly advantageous in the case of a conductor with a large cross-sectional area and / or a conductor consisting of several stranded wires.

The increase in the contact cross-sectional area is in principle also advantageous for other types of contacting, for example when contacting with a conductive adhesive, when contacting with an elastic, conductive material which is pressed against the conductor or in the case of soldered connections.

Conveniently, the conductor is an aluminum battery cable, especially for a motor vehicle, and the contact element is a battery terminal. In the field of motor vehicles, ladders made of aluminum are increasingly used for the purpose of saving weight. In particular, the battery cable, which has a very large cross section due to the high currents and therefore has a very high weight when using, for example, copper, a relatively high weight saving is made possible by the use of an aluminum cable. The electrical contact connection described here between such an aluminum battery cable and the battery terminal ensures a secure and permanent connection of the aluminum cable to the battery.

The object is further achieved according to the invention by a method having the features of claim 8. The in terms of electrical Contact compound cited preferred developments and advantages are to be transferred analogously to the process.

Conveniently, the particular thermal spraying method is chosen in this case and the spraying parameters are adjusted such that the conductive material at least partially penetrates into the conductor and at least partially penetrates an oxide layer possibly present on the conductor surface. In particular, when contacting an aluminum conductor, there is generally the problem that it has an insulating oxide skin, which would lead to a very high contact resistance in a normal clamping connection. Due to the penetration into the conductor and the associated material connection between the soft and the hard material, the aluminum oxide layer does not or hardly influences the contact resistance. Under material connection in this case the incorporation of hard material in the soft material of the conductor is understood, so that the hard particles are partially enclosed by the soft material.

Conveniently, to form the electrical contact connection, the conductor is overmolded with the conductive material and at the same time the electrical contact connection between the conductive material and the contact element is formed. The formation of the electrical contact connection is therefore in a one-step process only by the spraying of the conductive material, which at least partially covers the conductor and the contact element at the same time.

Alternatively, according to a preferred embodiment, a two-stage procedure is provided, wherein in a first step, the conductive material is sprayed onto the contact region of the conductor and in a second step, the contact with the contact element is made in particular by a mechanical clamping or pressure connection. Conveniently, in this case is formed by multiple overmolding of the contact region of the formed in particular as a hard metal tube sheath of the conductive material.

Fig. 1

einen endseitig abgeschrägten Leiter aus weichem Material mit einer aufgespritzten Stirnkappe in einer perspektivischen Seitendarstellung,

Fig. 2

eine Schnittansicht durch eine als Batterieklemme ausgebildete Kontaktklemme mit einliegendem Leiter und

Fig. 3

eine in einem einstufigen Spritzvorgang ausgebildete Kontaktverbindung zwischen einem Kontaktelement und einem Leiter.

Embodiments of the invention will be explained in more detail below with reference to FIGS. In each case, in schematic, highly simplified representations:

Fig. 1

an end bevelled conductor of soft material with a sprayed end cap in a perspective side view,

Fig. 2

a sectional view through a trained as a battery terminal contact terminal with incoming conductor and

Fig. 3

a formed in a one-step injection molding contact connection between a contact element and a conductor.

In the figures, like-acting parts are each provided with the same reference numerals.

In Fig. 1 is the stripped end of a particular designed as an aluminum conductor conductor 2 is shown. The conductor 2 has a plurality of individual conductors 4 designed in particular as stranded wires. The conductor 2 is for example a battery cable, which is intended for use in a motor vehicle.

At the end, the conductor 2 is surrounded in a contact region 6 by a jacket 8A designed in the manner of an end cap, made of a material that is harder than aluminum.

The jacket 8A is applied by means of a thermal spraying method, for example hot gas spraying or so-called flame spraying. By spraying the harder material on the soft material of the conductor 2, a secure, durable and in particular pressure-free connection is made between these two materials, so that there is no danger that the compound is affected by cold flow of the material of the conductor 2.

As the material for the jacket 8A, in particular, a nickel-chromium-nickel alloy is selected. The jacket 8A is formed by multiple over-molding with a sufficiently high wall thickness such that the jacket 8A overall has a high intrinsic rigidity and thus dimensional stability. The jacket 8A is therefore formed in the manner of a stiff tube.

The conductor 2 is obliquely cut at the end, so that in the frontal region a flat, approximately elliptical contact cross-sectional area 10 is formed. This has in comparison to the normal, in the case of a circular conductor circular conductor cross-sectional area 12 an enlarged area. By increasing the contact cross-sectional area 10, in particular in applications in which no skin effect occurs, for example in DC applications, only a small contact resistance is achieved.

Preferably, the angle a between a conductor longitudinal axis 14 and the slope 16 is at most about 60 °, as in Fig. 1 is shown. The smaller the angle chosen here, the larger the contact cross-sectional area 10.

In the embodiment of Fig. 2 is in particular the in Fig. 1 represented conductor 2 inserted in a trained as a battery terminal 18 terminal. The terminal is a contact element for contacting the conductor 2. The battery terminal 18 has two clamping halves 20A, B, between which the conductor 2 rests with the jacket 8A. To form the contact connection, the two clamping halves 20A, B are braced against each other via screws not shown here, which engage in screw receptacles 22, so that the conductor 2 is mechanically clamped in the battery terminal 18. The electrical contact connection is in this case indirectly via the jacket 8A, which surrounds the individual individual conductors 4 full circumference. By appropriate choice of material and choice of the wall thickness of the jacket 8, this is preferably designed such that even with a terminal in the battery terminal 18, the contacted via the jacket 8A individual conductors 4 are substantially free of pressure.

In contrast, in the embodiment of the Fig. 3 the electrical contact connection is formed such that the individual conductors 4 are first placed on a contact element 24 designed in the manner of a shell and that they are then over-molded with the harder material. Here, a single conductor 4 partially enclosing jacket 8B is formed, which with its flanks 26 at the same time with the surface of the contact element 24 in particular cohesive Connection is received. The individual conductors 4 are therefore enclosed between the contact element 24 and the jacket 8B.

The contact element 24 is formed here, for example, in the manner of a crimp sleeve, which is additionally, ie subsequently after the spraying of the jacket 8B, still deformed in order to achieve a mechanical attachment of the jacket 8B.

According to a preferred alternative embodiment, a mechanical fastening element is provided for additional mechanical fastening, which braces the jacket 8B against the contact element 24. This fastener is for example a screw which is screwed into an associated, threaded screw hole in the bottom of the contact element 24. The individual conductors 4 in this case would run around the centrally arranged screw. Alternatively, it is possible to provide a central sleeve which is connected to the bottom of the contact element 24 and which has, for example, an external thread on which a nut is screwed for clamping attachment. Conveniently, in this case, the contact elements 24 are formed such that they can be arranged one above the other and stacked, so that there are several connection levels. For this purpose, for example, a first contact element 24 is plugged or screwed with a bottom-side opening on the mentioned sleeve of another contact element.

Furthermore, it is expediently provided that the total height of the contact element 24 with the individual conductors 4 and the jacket 8B does not exceed a predefined maximum total height in order to be able to insert the contact element with the contacted individual conductors into a predefined flat sleeve, for example. The maximum total height is determined, for example, by the height of the trough-like contact element 24 seen in cross-section.

LIST OF REFERENCE NUMBERS

2

ladder

4

Single conductor

6

contact area

8A, B

coat

10

Contact cross-sectional area

12

Conductor cross-sectional area

14

longitudinal axis

16

slope

18

battery terminal

20A, B

clamp half

22

screw receiver

24

contact element

26

flank

a

angle

Claims (12)

1. Electrical contact connection between an electrical conductor (2) made from a soft material, in particular an aluminum conductor comprising a plurality of individual conductors (4), and a contact element (18, 24), characterized in that the conductor (2) is encapsulated at least partially in a contact region (6) by an electrically conductive material, which is harder than the soft material of the conductor (2), with the aid of a spraying process, with the result that there is a pressure-free electrical connection between the soft material and the sprayed-on material, and electrical contact being made with the contact element (18, 24) via the sprayed-on material.
2. Contact connection according to Claim 1, in which the conductor (2) is completely surrounded circumferentially in the contact region (6) by a sheath (8A) made from the harder material.
3. Contact connection according to Claim 2, in which the sheath (8A) is made from an Ni/Cr/Ni alloy.
4. Contact connection according to one of the preceding claims, in which a mechanical pressure connection or clamping connection is formed between the sprayed-on material and the contact element (18).
5. Contact connection according to one of the preceding claims, in which the conductor (2) has, at one end, a contact cross-sectional area (10) which is larger than the conductor cross-sectional area (12) and onto which the conductive material is sprayed.
6. Contact connection according to Claim 5, in which the conductor (2) is beveled at one end.
7. Contact connection according to one of the preceding claims, in which the conductor (2) is an aluminum battery cable, in particular for a motor vehicle, and the contact element is a battery terminal (18).
8. Method for producing an electrical contact connection between a conductor (2) made from a soft material, in particular an aluminum conductor, and a contact element (18, 24), characterized in that the conductor (2) is encapsulated at least partially in a contact region (6) by an electrically conductive material, which is harder than the soft material of the conductor (2), with the aid of, in particular, a thermal spraying process, with the result that a pressure-free connection is formed between the soft material and the sprayed-on material, and electrical contact being made with the contact element (18, 24) via the sprayed-on material.
9. Method according to Claim 8, in which the conductive material at least partially penetrates the conductor (2) and at least partially passes through an oxide layer which may be provided on the conductor surface.
10. Method according to Claim 8 or 9, in which the conductor (2) is encapsulated by the conductive material being sprayed on and, at the same time, the electrical contact connection between the conductive material and the contact element (24) is formed.
11. Method according to Claim 8 or 9, in which, in a first step, the conductive material is sprayed onto the contact region (6) of the conductor (2) and, in a second step, contact is made with the contact element (18) in particular by means of a mechanical clamping connection or pressure connection.
12. Method according to Claim 11, in which a sheath (8A) made from the conductive material is formed in particular by the contact region (6) being encapsulated by means of spraying a plurality of times.

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