Connection adapter

Abstract

Connection adapter with at least two electrically connected metal bodies of different material types 1 and 2, which has a connection line 5 consisting of the same metal as metal body 2 at one end of one metal body 2, wherein the two identical metals are electrically securely connected using thermal or mechanical methods and in the later production process, e.g. in the case of an electrical coil, a connection line 7 consisting of the same metal as metal body 1 is electrically securely connected using thermal or mechanical methods to the end of the second metal body 1 of the connection adapter.

Description

[0001] The invention relates to an electrical connection between metal bodies of different material types, in particular an electrical connection between aluminum (hereinafter sometimes abbreviated to "AL") and copper (hereinafter sometimes abbreviated to "CU"), which is widely used in electrical networks and supply devices of all kinds.

[0002] It is known that there are electrical connections in the form of adapters with which metal bodies of different material types, for example aluminum plates with copper plates, can be electrically connected.

[0003] One such variation on the market are the so-called "AL-CU washers". These can consist of two washer-like elements, one made of aluminum (AL), the other of copper (CU). These adapters can be pressed together using special processes, e.g., with high forces, welded, or created using galvanic processes. The electrical connection between the two metals can be described as permanently good. The respective aluminum components of the connecting cable, e.g., in the form of an aluminum or copper ring eyelet, can then be attached to the respective side in a metal-separated manner, i.e., the ring eyelet with the aluminum conductor on the aluminum side, the ring eyelet with the copper conductor on the copper side. This can prevent the formation of galvanic elements that could lead to corrosion.

[0004] There are also adapters manufactured using a similar process, but with an aluminum sleeve on one side and a copper ring eyelet on the other. An aluminum conductor, such as stranded or rigid wire, can be inserted into the aluminum end and crimped using special tools. To prevent immediate oxidation on the aluminum, the conductor should first be cleaned and protected against further oxygen ingress with chemicals (e.g., Vaseline) before crimping. On the copper end, the ring eyelet is attached to a copper lug, for example, with a screw.

[0005] However, with these existing systems, it may be necessary to check the connections regularly or, in the case of screw connections, to retighten them at specific intervals. The reason for this is that aluminum tends to "flow" over time, meaning that pressure-loaded areas yield, resulting in a deterioration of the electrical connection or a noticeable increase in contact resistance.

[0006] Furthermore, aluminum has a much greater tendency to crack or break than copper. Therefore, if you move an aluminum conductor back and forth, for example, when connecting it to a terminal, the first cracks and thus weak spots can appear unnoticed, which can also cause the electrical resistance to increase further down the line.

[0007] It is also known that aluminum strip can be joined to copper rods or copper strands, which may be pre-compressed with a copper sleeve, using the cold-pressure welding process. These joints are considered to be permanently good.

[0008] However, this can require complex machinery for the cold-pressure welding process and also place high demands on precision, making it difficult to implement directly on a winding machine for electrical coils, for example. Furthermore, this process cannot reliably join thicker aluminum flat enameled wires or round enameled aluminum wires to copper. Nor can it be used to join round enameled copper wires to the aluminum strip.

[0009] There are also special tinned crimp connectors made of copper or brass on the market, which have internal "teeth" and can also be tinned. These connectors can accommodate an aluminum conductor on one side and a copper conductor on the other. When the crimp connectors are mechanically pressed together, the teeth work their way into the respective conductors. This can cause two problems: the tendency of the aluminum to flow can lead to microscopic "lifting off," and the tinned surface does not form a metallurgical bond with the aluminum, but merely rests on it. Therefore, directly after pressing together, there is only a force or form fit.

[0010] These commercially available electrical connections can therefore have the disadvantage of either handling problems at the moment of wiring or problems due to high maintenance costs or that long-term contact problems can occur due to increased electrical resistance.

[0011] Furthermore, the patents DE102018107485A1 and US4315175A describe additional designs of how copper and aluminum conductors can be connected.

[0012] Patent DE102018107485A1 describes an adapter with an inner core made of aluminum that is encased in copper on the outside. To connect to another aluminum conductor, the copper surface in the connection area is removed, revealing the aluminum underneath. The conductor to be connected is inserted into a previously prepared opening in the aluminum and then fixed, for example, mechanically or thermally - e.g., by welding. On the other side, a ring eyelet is attached to the copper surface using a screw. This design, however, has the disadvantage that encasing the aluminum with copper is only possible using special processes and cannot easily be implemented in the manufacturing industry, e.g., by manufacturers of winding goods.

[0013] Patent US4315175A essentially describes an adapter consisting of a cold-press-welded unit in which a copper plate is pressed onto an aluminum plate, at the respective ends of which aluminum or copper strands are pressed together using a compression connector. This compression connector consists of a sleeve that encloses the strands.

[0014] This creates a crimp at each end that is “single-type”, i.e. aluminum stranded wire is pressed onto an aluminum plate and a copper stranded wire is pressed onto a copper plate.

[0015] In the latter patent US4315175A, the "pure" connection is indeed obtained, but here too, due to the physical properties of aluminum, it is to be expected that the compression of the aluminum sleeve and the aluminum strand may give way after a longer period of time due to the tendency of aluminum to flow.

[0016] The present invention is based on the object of designing a new electrical connection that does not have these disadvantages. This object is solved by the features of the independent patent claim. The resulting advantages may include: ▪ that a continuous intermetallic phase or metallurgical compound of different metals can be at least significantly improved or ensured, ▪ that corrosion problems, e.g. through galvanic processes, and also oxidation problems can be reduced, ▪ that the flow properties of metal bodies such as aluminum become less relevant and therefore regular maintenance may not be required, ▪ that a process-reliable connection of different metal bodies, e.g. aluminum conductors and copper conductors, can also be made directly on a machine for the production of winding goods or electrical coils, ▪ that the risk of cracks forming can be noticeably reduced or eliminated by subsequent bending of sensitive connecting cables such as aluminum conductors or by strong vibration

[0017] The term "material type" refers to a material or alloy with one predominant element. Two different material types therefore mean that one material type has one predominant element, such as copper, while the other material type has a different predominant element, such as aluminum.

[0018] In detail, there are now various possibilities for designing and developing the electrical connection according to the invention. For this purpose, reference is made, on the one hand, to the claims subordinate to claim 1 and, on the other hand, to the description of a preferred embodiment in conjunction with the drawings. In the drawings, the same reference numerals are used for the same units. They show: Fig. 1: Representation of the base part of the electrical connection as a longitudinal section Fig. 2: Representation of the base part of the electrical connection as a top view Fig. 3: Representation of the connection adapter with base part and a conductor already attached on one side as a longitudinal section Fig. 4: Representation of the connection adapter with base part and a conductor already attached on one side as a top view Fig. 5: Representation of the connection adapter with base part and conductors attached on both sides as a longitudinal section Fig. 6: Illustration of the connection adapter with base part and conductors attached on both sides as a top view Fig. 7: Illustration of the connection adapter with base part and conductors attached on both sides, with the conductors laid in the same direction

[0019] Fig. 3 and Fig. 4 show a first embodiment of the connection adapter according to the invention.

[0020] The connection adapter consists of Fig. 1 and Fig. 2 essentially consists of two metal bodies, preferably a copper plate 2 and an aluminum plate 1, which are electrically connected at one or more connection points 3. These two metal bodies can form the base part mentioned in the description of the figures. This connection point 3 can be realized using welding processes. Preferably, the cold pressure welding process can be used, wherein a stamp can be pressed with high pressure onto the first metal body, e.g. aluminum, which can penetrate into the second metal body, e.g. copper, and can thereby ensure that a metallurgical bond is created between the two different metals at the transition point 4 in the resulting depression.

[0021] A secure electrical connection can be significantly improved if the process parameters are controlled during the cold pressure welding process. These include, in particular, the pressing pressure of the punch, the surface area of the punch, the depth of the punch, and the hardness of the metal bodies, particularly when it comes to copper or aluminum. Likewise, the thicknesses of the two materials can be matched to ensure that the metal bodies, such as aluminum, do not crack, particularly during pressing. The pressing time should also be strictly adhered to. Pretreatment of the metal surfaces may also be necessary to remove any oxidation products. This can be achieved, for example, by grinding.

[0022] In the adapter according to the invention, the typical material thicknesses of the metal bodies in the case of aluminum and copper as described below as a preferred embodiment, for aluminum between 1 mm and 3 mm, preferably between 1.25 and 2.75 mm, more preferably between 1.5 and 2.5 mm, and for copper between 3 mm and 5 mm, preferably between 3.25 and 4.75 mm, more preferably between 3.5 and 4.5 mm.

[0023] These dimensions can represent a good compromise between the overall size, since the connection adapter must be able to be inserted into the winding in as space-saving a way as possible, and the handling and stability, e.g. during later soldering.

[0024] With this material thickness pairing, stamp surfaces (ie the later welded cross-section) per stamp of 10 mm 2 up to 25 mm 2 be advantageous, preferably they are in the range of approx. 15 mm2 up to 20 mm 2 Depending on the punch surfaces, pressing forces of approximately 30 to 50 kN (kilonewtons) per punch may be particularly suitable.

[0025] The stamping depth can range from 4 mm to 6 mm, preferably approximately 5 mm. The typical pressing time for favorable results can be approximately 5 seconds.

[0026] A low copper hardness can be advantageous. The required copper hardness can be adjusted by annealing the copper at 500 °C for approximately 60 minutes, resulting in a Vickers hardness value between HV50 and HV60, but preferably below HV55.

[0027] At higher temperatures, the annealing time can be significantly reduced.

[0028] Further options for optimizing the hardness setting are described below.

[0029] The intermetallic bond between copper and aluminum can be improved if the hardness of the metals before annealing is greater than 1.6 times the hardness after annealing and a cold rolling process - this applies to both copper and aluminum.

[0030] Furthermore, subsequent diffusion annealing of the resulting cold-press welded unit or base part at temperatures between 150°C and 550°C with times adjusted to the diffusion annealing temperature can further improve the intermetallic bond.

[0031] These parameters can therefore have a positive influence on the intermetallic phase or metallurgical bond, e.g. between copper and aluminum.

[0032] A further advantage of the connecting adapter according to the invention can be that it can be cost-effectively prefabricated in large quantities in efficient series production, e.g., in a production island or on a production line. This means that only a pure soldering process between the metal body 1 of the connecting adapter and the connecting cable 7 may be necessary on the winding machine itself—in the preferred embodiment described above, this is between the aluminum plate and the aluminum conductor.

[0033] Since, in addition to the pure component geometries of the metal body, e.g. the copper plate or the aluminum plate, or their cross-sectional areas, the welded cross-section must also be suitable for the current conduction, several cold-press welded joints or larger cold-press welded joints can be provided depending on the level of the current.

[0034] Alternatively, the cross-sections or thicknesses of the two materials can be increased or decreased. The process parameters described above can then be adjusted accordingly.

[0035] Soldering the connecting cable 5 onto the metal body 2 of the base part according to Fig. 3 and Fig. 4, in the above-mentioned preferred embodiment, the copper conductor 5 to the copper side 2, can be made before the cold pressure welding process is carried out. To improve the reliability of the connection, the connection can preferably be made using a brazing process, starting Fig. 3 marked as solder connection 6.

[0036] The sequence of production steps described above can have the advantage, especially when using copper as the metal body, that the copper plate is already thermally heated during the brazing process, thus "annealing" the copper material and becoming correspondingly softer. This brazing process automatically adjusts the copper hardness described above. Since the temperatures during brazing can be very high, the brazing process itself can be sufficient to sufficiently reduce the copper hardness for the subsequent cold-pressure welding process.

[0037] It can be particularly advantageous to perform the cold-pressure welding with the other metal body 1, e.g., the aluminum, only after this thermal brazing process. In particular, if, in the example, the copper conductor 2 were to be soldered to the base part only after the cold-pressure welding, the high temperatures during copper brazing could damage the aluminum-copper cold-pressure welded joint due to copper's excellent thermal conductivity. The reason for this is that the typical brazing temperatures for copper connections are above the melting point of aluminum.

[0038] According to a particularly advantageous further embodiment, it is provided that the connecting line 5, i.e. in the present embodiment the copper conductor, according to Fig. 3 and Fig. 4 can be attached lengthwise to the base part. This can have the advantage that the connecting adapter can then later be placed lengthwise to the coil or winding direction, making it easy to create so-called taps, which can be used, for example, in a transformer for tapping different voltages.

[0039] Another technically useful design is that, depending on the subsequent current load, several connecting conductors can be attached and the current can be conducted in parallel. Fig. 4 shows two copper conductors as an example.

[0040] The resulting connection adapter is then connected to the winding in such a way that Fig. 5 and Fig. 6, a connecting cable 7 is joined to the metal body 1 of the connecting adapter, in the described embodiment, the aluminum conductor to the aluminum plate. While this can also be done using a welding or cold-pressure welding process, it can be done in a very user-friendly way using a soft soldering or brazing process, since this process can be implemented without great effort directly near the coil on the winding machine - starting from Fig. 5 marked as solder connection 8.

[0041] Advantageously, the brazing process can also be used here to connect the connecting adapter to the connecting cable 7—particularly in the case of aluminum—because the metallurgical contact can be more intensive and thus more durable than with the soft soldering process. When using aluminum, depending on the brazing additive, brazing or working temperatures between 550°C and 650°C are required, preferably between 580°C and 610°C, and more preferably 590°C. An alloy of pure aluminum and silicon can be advantageous for use as a brazing additive.

[0042] The silicon content of the brazing filler can preferably be 12%, as this reduces the melting or working temperature of the brazing filler to the aforementioned temperature of approximately 590°C. The selection of the brazing filler can have a significant impact on the brazing process. Especially if the brazing filler is not selected appropriately, higher working temperatures may be required, at which the aluminum plate 1 or the aluminum conductor 7 may melt.

[0043] A suitable flux or soldering paste should also be used so that the brazing alloy can flow optimally and without air voids between the materials to be soldered.

[0044] However, if the complete connection, including the cold-press welding, were to be carried out on the winding machine, the following problem would arise: In some embodiments, the entire connection, including the cold-press welding connection, can be performed on the winding machine. However, the cold-press welding connection described above for producing the adapter according to the invention would require compliance with all process parameters in such embodiments, as well as large, complex pressing machines, which cannot be used in the immediate vicinity of the winding during the production of a winding due to the large space requirements. In addition, spatial flexibility may be lacking because the connection point for the two connecting cables on the coil winding is determined by the winding process and because it can be difficult to position the pressing dies of the pressing machine exactly at this point.

[0045] The advantage of this solution can be that a connecting cable 5, preferably made of copper, is available outside the coil, which can be electrically and safely connected to the onward cable structure using all conventional and known solutions, e.g. with terminals, with ring eyelets, with soldering processes, etc., and an electrical transition can be realized within the coil, which can also be permanently electrically safe due to the intermetallic phase or the metallurgical connection and, for example, does not place any adverse mechanical stress on the aluminum conductors of the winding itself.

[0046] According to a special application, it is planned that connection adapters of different sizes are realized depending on the current loads or the conductor cross-sections.

[0047] A further advantageous implementation of the invention is according to Fig.7 is that the connecting wire 2, in the example described, the copper conductor, is not attached lengthwise in the opposite direction to the aluminum plate 1 as described above, but rather pointing in the same direction or arranged at any angle. This can make it possible to use the connection adapter even if the tap is, for example, located at the very right edge of a coil instead of the left edge, and therefore needs to be as short as possible so that the connection adapter remains within the winding.

[0048] In general, the connection adapter can ensure that a continuous intermetallic phase or metallurgical bond can be realized or at least optimized. This can prevent corrosion problems, e.g., caused by galvanic processes, or oxidation problems. The flow properties of the metal bodies, especially aluminum, can become less relevant, which may make regular maintenance unnecessary. A largely process-reliable connection of connecting lines 7 and 5, e.g., aluminum conductors and copper conductors, can also be achieved directly on a machine for the production of winding materials or electrical coils.

[0049] Likewise, the connection adapter can preferably be fully integrated into the coil winding, so that subsequent bending of, for example, aluminum conductors significantly reduces the associated risk of cracking.

[0050] If the connection adapter must be installed outside the coil, it can be fixed to avoid excessive mechanical stress. In this case, the entire connection can preferably be mechanically stabilized, e.g., by using heat-shrink tubing. This also prevents the introduction of moisture or salts, etc., which would promote the development of potentially critical galvanic processes.

[0051] As already described above, the present invention particularly also relates to the method for producing a connection adapter comprising a copper plate 2, an aluminum plate 1, and at least one copper conductor 5. The method comprises connecting the copper conductor 5 to the copper plate 2 by means of a brazing process, wherein the hardness of the copper plate is reduced by thermal heating during the brazing process sufficiently for a subsequent cold pressure welding process. In other words, the copper material is advantageously already "annealed" and correspondingly softened during the brazing process, so that the above-described adjustment of the copper hardness already takes place within the framework of the brazing process.

[0052] Subsequently, i.e., after joining the copper conductor 5 to the copper plate 2 using a brazing process, the copper plate 2 and the aluminum plate 1 are joined together using a cold-pressure welding process. The process may additionally include diffusion annealing of the cold-pressure welded unit at temperatures between 150°C and 550°C, with a time period adjusted to the diffusion annealing temperature, to further improve the intermetallic bond.

[0053] The method according to the invention has several advantages: Firstly, a connection adapter is provided which already comprises the copper conductor 5, so that it does not have to be subsequently connected to the copper plate 2. This is advantageous because a thermal soldering process between the copper plate 2 and the copper conductor 5 after the cold pressure welding of the aluminum plate 1 and the copper plate 2 could damage the aluminum-copper cold pressure weld due to the high temperatures during copper brazing and the excellent thermal conductivity of the copper. In particular, the temperatures during copper brazing are typically above the melting temperature of aluminum. The entire aluminum plate can melt in the process, with the cold press area being particularly at risk due to the thinner aluminum wall thickness caused by the pressing process.

[0054] Second, at the temperatures required for copper brazing, the copper is automatically subjected to an annealing process, which advantageously reduces its hardness. This can result in a Vickers hardness value between HV50 and HV60, and more preferably below HV55. This reduced hardness is advantageous for the cold pressure welding process.

[0055] In other words, the present invention is concerned with the fact that the connection adapter comprises the copper wire 5 and that this wire is connected to the copper plate 2 before the copper plate and the aluminum plate are joined together by means of cold pressure welding.

[0056] When using the connection adapter produced in this way, only the aluminum plate 1 needs to be connected to the corresponding aluminum conductor 7. While this can be done using a welding or cold-pressure welding process, the connection can advantageously be made using a soft soldering or brazing process, since this process can be implemented without great effort directly near the coil on the winding machine. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 102018107485A1 [0011, 0012] US 4315175A [0011, 0013, 0015]

Claims

[1] Method for producing a connection adapter, wherein the connection adapter comprises two metal bodies comprising a copper plate (2) and an aluminum plate (1), as well as at least one copper conductor (5); the procedure includes: Connecting the copper conductor (5) to the copper plate (2) by means of a brazing process, wherein the hardness of the copper plate is reduced by thermal heating during the brazing process sufficiently for a subsequent cold pressure welding process, then joining the copper plate and the aluminum plate using a cold pressure welding process. [2] Method according to the preceding claim, wherein the copper hardness after the brazing process preferably has a value for the Vickers hardness between HV50 and HV60, but preferably below HV55. [3] Method according to one of the preceding claims, wherein the method comprises pretreating surfaces of the metal bodies to remove oxidation products, preferably grinding surfaces of the metal bodies. [4] A method according to any one of the preceding claims, wherein the method additionally comprises: diffusion annealing the cold press welded unit at temperatures between 150°C and 550°C with a time adjusted to the diffusion annealing temperature. [5] Method according to one of the preceding claims, wherein a material thickness of the copper plate (2) is between 3 mm and 5 mm, preferably between 3.25 mm and 4.75 mm, more preferably between 3.5 and 4.5 mm; and a material thickness of the aluminum plate (1) is between 1 mm and 3 mm, preferably between 1.25 and 2.75 mm, more preferably between 1.5 mm and 2.5 mm. [6] Connection adapter with at least two metal bodies of different material types (1) and (2) and a connecting line (5) fastened to at least one side of the connection adapter, wherein the two metal bodies comprise a copper plate (2) and an aluminum plate (1) and the at least one connecting line (5) is a copper conductor (5); characterized by that the metal bodies (1) and (2) are cold-press welded together and that the at least one copper conductor (5) is electrically connected to one side of the copper plate (2) via a brazing process. [7] Connection adapter according to claim 6, characterized by that more than one connecting cable (5) is attached to the copper plate (2) on one side of the connection adapter.

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