PLATED BIMETAL

Description

[0001] The invention relates to a clad bimetal for connector partners with the ability to deform as a result of a temperature change and to conduct electrical energy, comprising a bimetal with two layers of metals with different coefficients of thermal expansion and two outer layers consisting of a copper-based material.

[0002] For contacting or creating detachable electrically conductive connections, plug connectors, contact elements, pole connectors, sockets, etc., are used in a wide variety of designs and variants. Particularly, but not exclusively, for electrical contacting tasks in the higher power range, contact systems have been developed that are based on circular contact geometries for receiving a contact pin and whose starting material consists of a planar contact grid that is hyperbolically twisted into the circular contact geometry. These contact systems, known as RADSOK, are characterized by robust and high-density contact formation due to the considerable contact area with the respective contact pin. Alternatively, instead of the hyperbolic twisting, inwardly directed lamellar geometries are known, whose lamellar contact grid is radially symmetrical.

[0003] These contact geometries, preferably used as high-current contact sockets, are therefore known as radial contact sockets or hyperbolic contact sockets.

[0004] RADSOK contact systems of the aforementioned type are received into connector socket sleeves via their generally cylindrical outer contours and achieve external contact via the cylindrical surfaces. DE 10 2007 051 266 B4 is based on the fundamental idea of ​​providing a single connector socket sleeve designed to accommodate different lamellar contact cages in the form of RADSOK contact sockets, which make contact with the inside of the contact sleeve.

[0005] A comparable basic structure is shown in DE 20 2016 100 095 U1. The subject matter of the invention here is the coupling, connection, and contacting of the cylindrical lamellar cage "floating" within the receiving connector socket sleeve, by fixing only one of the respective end flanges in the socket, for example, by press fit. An electrical connector socket comprising a cylindrical socket sleeve is provided, which is designed with a receiving space in which a cylindrical lamellar cage with a plurality of parallel contact lamellae is inserted, wherein the lamellar cage has a first and second circumferential flange between which the contact lamellae extend. The lamellar cage is fixed at one end at least axially and preferably also rotationally fixed in the socket sleeve and thereby clamped.The lamellar cage is attached to the inner wall of the bushing sleeve by means of a fastening element on the sleeve side, and at the other opposite end, an axial sliding bearing is provided that is rotatable at least through a certain angle of rotation. Preferably, the lamellar cage with its single flange is attached to the inner wall of the bushing sleeve by means of a fastening element on the sleeve side.

[0006] Especially in high-current contact applications—for example, charging batteries in electric vehicles or connecting the vehicle battery to the vehicle's electrical components—reliable electrical contact between the connectors is crucial. Such connectors and their contact elements, which often consist of one or more pairs of pins and sockets, are subject to various influences, such as mechanical stress, vibrations, shocks, and aging. Significant temperature fluctuations, caused by environmental conditions or by self-heating due to the electrical current flow and the inherent resistance of the current-carrying components, are also possible.Self-heating can be particularly relevant at the contact points, as the contact areas are small due to the contact force, resulting in a high resistance almost geometrically induced by the contact. For this reason, it is crucial that the contact force – more precisely, the normal contact force – is as high as possible and remains constant to press the contact partners, usually formed by a contact pin and a contact socket, firmly together at their contact surfaces for electrical connection.

[0007] The contact sockets available in the prior art, such as the aforementioned RADSOK sockets or their plug-in contacts (the plug-in pins), utilize both formative shaping processes such as stamping and rolling, and suitable materials with spring properties to generate the desired spring action through restoring forces. These forces are used to create preferably elastic contact forces between the contact partners at their contact surfaces. The performance of the plug-in connection is limited by temperature effects, as higher temperatures cause a loss of spring force due to relaxation processes, material creep, and residual stress reduction. This is particularly true for copper and copper alloys, since copper, in addition to its generally low elasticity, becomes "soft" even at low temperatures.

[0008] If the plug contact partners are designed in this way and made from materials such as spring steel, it is indeed possible to generate very high normal contact forces that reliably press the contact surfaces of the plug contact partners together, but assembly problems often arise because plugging the contact partners together requires high insertion forces, which make assembly difficult or require the use of tools.

[0009] To mitigate the problem of decreasing contact normal forces under temperature influence, contacting solutions have been developed in which the contacting elements or additional components deform as a result of the temperature increase, thereby increasing the contact force while simultaneously reducing the assembly force required when mating the connector at lower temperatures. EP 2 461 427 B1 discloses a self-deforming high-current contact based on the approach of achieving low mating forces at room temperature for assembly and high contact force or contact normal force during operation, particularly under conditions of increased self-heating and elevated ambient temperatures, through the design of the high-current contact and the provision of a connector element that deforms automatically with rising temperature.

[0010] The contact normal force increases almost automatically as soon as a temperature rise occurs. The proposed high-current contact serves to transmit current from a power source to an electrical conductor of a current collector. Thus, the high-current contact, together with the corresponding contact pin, serves both as a mechanical connection and as an electrical contact between the current collector and the power source via an electrical contact surface between the high-current contact and the contact pin. By increasing the mechanical connection through temperature-induced deformation of the high-current contact or the self-deforming components, particularly a ring-shaped element, as the temperature of the high-current contact rises due to current flow, the material-related loss of contact normal force is counteracted, and the contact force is at least maintained, and in some cases even increased.At the same time, assembly is possible at low temperatures with reduced insertion force.

[0011] A similar approach is pursued in DE 10 2005 032 462 A1. This patent teaches how to design the contact socket in such a way that at least the area of ​​the contact tips consists of a bimetallic strip. The area made of the bimetallic strip changes its shape due to the influence of heat. This change in shape is used to at least keep the contact normal force constant or to increase it.

[0012] The contact solutions available in the prior art, which involve temperature-dependent changes in the contact normal force and are constructed using a combination of contact socket and contact pin, exhibit some significant disadvantages. Solutions often incorporate one or more components, such as rings or tubular parts, which influence the contact normal force due to temperature changes. These solutions are complex, require multi-part contact assemblies, are therefore more difficult to assemble, and have a higher potential for assembly errors. This results in economically unfavorable solutions and increases the likelihood of malfunctions.

[0013] Other contact designs integrate the temperature-deforming components of the contact or connector into the contact socket component. While such geometric designs allow for a simple contact partner structure due to temperature-dependent deformation, materials with temperature-dependent deformation properties are not good conductors of electrical energy because their electrical resistance is lower. This material property results in electrical power losses and increased heating and temperature rise of the bimetallic contact elements. This problem is particularly relevant when these contact partners are used in connectors for high-voltage applications.

[0014] This problem is known in the prior art. DE 30 45 700 A1 discloses a plug connection with a socket whose spring clips are made of a thermobimetallic material and are dimensioned such that, at ambient temperature, the socket is sufficiently open to receive the plug pin intended for it, while at operating temperature it exerts a pressure on the plug pin that is greater than the pressure achieved solely by the elastic deflection of the socket when inserting the plug pin. The teaching of DE 30 45 700 A1 recognizes that bimetallic materials have inferior electrical conductivity properties and that it is therefore advantageous for the bimetal to have an additional, highly conductive layer, i.e., for the bimetal to consist of three or more layers, one of which is made of a highly conductive material.

[0015] EP 0 659 548 discloses a clad bimetal according to the preamble of claim 1.

[0016] To produce these multilayer metals, consisting of a bimetal formed from two materials with differing coefficients of thermal expansion and at least one other highly conductive material, it is known to provide bimetals with electrically conductive surface layers by means of an electroplating process. Electroplating copper requires high electrical energy and / or chemical substances for the electrolyte bath, which cause environmental pollution. Furthermore, the achievable layer thicknesses are very thin.

[0017] The object of the invention is to further develop existing bimetallic materials with temperature-induced deformation properties for electrically conductive connectors and to at least partially reduce the existing disadvantages.

[0018] To solve this problem, the invention proposes a clad bimetal. For this purpose, a bimetal, i.e., a material consisting of two metal layers with different coefficients of thermal expansion, is provided with a copper-based top layer and a copper-based bottom layer by roll cladding. This means that the thickness of the outer copper layers thus formed can be selected over a wide range due to the roll cladding process and can be significantly greater than the thicknesses achievable by electroplating. This allows for copper layer thicknesses that exhibit very good electrical conductivity due to the resulting low electrical resistance.

[0019] The outer copper-based layers forming the surfaces, consisting of a copper top layer and a copper bottom layer, do not affect the temperature-induced deformation properties of the bimetal, or only to a minimal extent, because they are arranged symmetrically on the top and bottom of the bimetal. However, a time-delayed deformation due to temperature changes may occur, as the heat energy must first penetrate the copper layers.

[0020] The clad bimetal proposed according to the invention is particularly suitable as a semi-finished product and thus as a starting material for connector partners with temperature-induced deformation properties, such as contact sockets, contact plugs, contact pins, intermediate sleeves and other contact partner elements, since connector partners often require the properties supported by the clad bimetal. Changes in contact normal force at different temperatures due to temperature-induced deformation of the clad bimetal and good electrical conductivity due to the low electrical resistance of the copper layers of the clad bimetal with its provided copper layer thicknesses. must be able to realize this.

[0021] The manufacturing process of roll cladding is economically feasible in a continuous process and offers the additional advantage of eliminating electroplating with its environmentally harmful effects. Furthermore, the clad bimetals can be easily processed in terms of geometry and dimensions by stamping and cold or hot forming, such as rolling or bending, and further processed into connector components economically and for mass production.

[0022] The invention is explained in more detail below with reference to an exemplary embodiment in conjunction with the figure. The figure shows: Fig. 1 the schematic, perspective view of the plated bimetal. In the Figure 1 The sandwich-like structure of the clad bimetal 1 is shown. The bimetal 10 is arranged between two outer copper-based layers 20. The outer copper-based layers 20 are preferably of approximately the same thickness to each other and to the bimetal 10 and are bonded to the bimetal 10 by a roll cladding process, essentially forming a metallurgical bond. Particularly good and intimate metallurgical bonds between the copper-based layers 20 and the bimetal 10 can be achieved by roll cladding processes at elevated temperatures. This is especially economical because the copper-based layers 20 are roll-clad directly after their production (e.g., continuous casting followed by processing into thin sheets) at the "first firing" and thus at the existing elevated temperature. Reference symbol list

[0023] 1-clad bimetal 10-bimetal 20-layer of copper alloy, copper layer

Claims

1. Clad bimetal (1) for plug connection partners with the ability to deform as a result of a change in temperature and the conduction of electrical energy, comprising a bimetal (10) having two layers of metals with different coefficients of temperature expansion and two outer layers (20), consisting of a copper-based material, characterized in that the outer copper material-based layers (20) are applied by roll cladding, characterized in that the layer thickness ratio between each copper material-based layer (20) and the bimetal (10) is approximately 1.

2. Clad bimetal (1) according to Claim 1, characterized in that the copper material-based layers (20) have largely the same layer thickness.

3. Plug connection partner with deformation properties induced by a change in temperature, comprising a clad bimetal (1) according to any of the preceding claims.