busbar

Abstract

The present invention relates to a busbar, particularly for high-current applications, comprising a base body made of aluminum or an aluminum alloy and a connection area for connecting to other electrical components. The section of the base body associated with the connection area has a recess that reduces the thickness of the base body, into which a connection part made of copper or a copper alloy is inserted. The base body and the connection part are joined to one another by means of a melting joining process at least at one contact surface of the recess, such that a composite structure of the materials of the base body and the connection part is present in this area. The invention also relates to a busbar arrangement with such a busbar and to a method for manufacturing such a busbar.

Description

[0001] The present invention relates to a busbar, in particular for high-current applications, with a base body made of aluminum or an aluminum alloy and a connection area for connecting to other electrical components.

[0002] Both in the automotive sector and within the associated infrastructure (e.g., chargers), aluminum alloys are increasingly being used as current conductors for weight reasons or due to the limited availability of certain metals (such as copper). Due to its high chemical reactivity, the use of aluminum is particularly sensitive, particularly at high current intensities. This means that special measures are necessary to shape the connection area appropriately. The connection area can be connected to another busbar or to other electrical components. Busbars are often produced from sheet metal strip and are usually bent using suitable bending processes so that they can bridge connection distances in the vertical and / or horizontal direction.For this reason, busbars usually have a solid cross-section (e.g., rectangular), at least outside the connection area, which provides appropriate self-supporting stability and sufficient conductor cross-section. The term "high-current applications" depends on the specific area in which the busbar is used. Automotive applications and the corresponding charging infrastructure generally refer to currents of over 300 amperes.

[0003] It is the object of the present invention to improve a busbar of the type mentioned at the outset with regard to its connection area.

[0004] To this end, the invention provides that the section of the base body assigned to the connection area has a recess that reduces the thickness of the base body and into which a connection part made of copper or a copper alloy is inserted. The base body and the connection part are joined to one another at at least one contact surface of the recess by means of a melting joining process in such a way that a mixed structure of the materials of the base body and the connection part is present in this area. This design provides several advantages. Firstly, the connection area is flat because at least part of the connection part is accommodated in the thickness direction of the base body.To prevent the problem of diffusion through the contact surface between the two material partners of the base body and the connection part, this is already achieved through the type of melting joining process and is therefore largely completed after cooling. In addition, the formation of foreign layers (e.g. oxides) in the area of ​​the current transfer point between the base body and the connection part is prevented. This results in a permanent installation of the connection part, which connects two different metals together using a suitable manufacturing process. The main advantage is that a deterioration in the contact resistance between the base part and the connection part, which could occur over time, is counteracted. Furthermore, the permanent connection between the base body and the connection part eliminates the need for additional components such as intermediate washers or protective pastes.This streamlines assembly processes. This particularly facilitates the use of aluminum or aluminum alloys. The bond is formed by the local introduction of energy at the interface between the two metals. This causes the metals to enter a liquid state, allowing them to mix. In this case, an intermetallic bond is achieved between the two insoluble metals.

[0005] Preferably, the recess can have a stepped shape such that a connecting section of the connecting part essentially fills the stepped shape and is covered by a section of the base body on the side of the base body facing away from the connection side. The connecting part and the base body thus overlap both in the thickness direction and in the longitudinal direction of the busbar. This enables a precise fit. Furthermore, a stepped shape is technically very simple to manufacture.

[0006] According to an advantageous embodiment, the connecting part can be designed as a flat, flat part with a thickness greater than the depth of the recess. The connecting part can be punched out of sheet metal and then already has its final shape after the punching process. This allows for cost savings.

[0007] The thickness of the connecting part can preferably be 0.5 to 0.9 times, preferably 0.65 to 0.8 times, the thickness of the section of the base body assigned to the connection area. Copper or copper alloys are very good conductors, and this measure allows for even further cost savings. Furthermore, it also ensures good connection and integration in the recess without the connection area increasing in thickness excessively.

[0008] In a further variant, the connecting part protrudes beyond the connection side of the base body, preferably by 0.1 to 0.3 times its thickness. The connecting part advantageously protrudes far enough that in the connection area, only the connecting part makes contact with the other electrical components. This prevents any direct contact between the base body and the connection point on the other electrical components. The preferred proportion of 0.1 to 0.3 times the thickness of the connecting part is sufficient to achieve a suitable gradation between the connecting part and the base body, so that the desired distance between the base body and the connection point of the electrical components is always maintained.

[0009] Furthermore, the contact surface of the recess can have a width B, wherein the region with the mixed structure in the contact surface plane extends over a width that corresponds to at least 0.5 times, preferably at least 0.7 times, the width B of the recess. This ensures that the mixed structure is formed over the largest possible section, viewed in the longitudinal direction of the busbar, and the corresponding advantages are provided. Viewed in the width direction of the busbar, the formation of the mixed structure can extend across the entire width of the base body.

[0010] Preferably, the connection of the base body and the connecting part can be effected by means of the melting joining process through the overlapping section of the base body. This means that the thickness of the base body is completely melted at the corresponding point, while the penetration depth into the connecting part can be adjusted according to the circumstances. As a rule, it is preferred if the penetration depth into the copper material is very shallow, so that the underside (connection side) of the connecting part is not affected by the process. Furthermore, this ensures that, in terms of thickness, the mixed structure extends further into the base body than into the connecting part.

[0011] In an advantageous embodiment, which is very simple and cost-effective to manufacture, the connecting part is designed as a stepped, offset extension of the base body. Therefore, the base part and connecting part only overlap on one side. The connection area is therefore largely formed by the connecting part.

[0012] However, it is also entirely possible for the connecting piece to be designed as a disc-shaped insert that is inserted into a recess with a closed circumference. Round, particularly circular, designs are particularly suitable for this purpose. For example, the base body can be provided with a stepped bore into which a correspondingly round disc or flat ring is then inserted, e.g., pressed, as a connecting piece. This already ensures a very precise and good pre-assembly of the connecting piece on the busbar, so that the melting joining process can also be carried out independently of this prefabrication (e.g., at a different location).

[0013] The invention also relates to a busbar arrangement comprising a busbar according to any one of claims 1-9 and an electrical component connected to this busbar. A gap remains between the connected electrical component and the portion of the base body associated with the connection area, and indirect contact between the busbar and the electrical component is only achieved via the connection part. Current transmission then occurs via the mixed structure of the materials of the base body and the connection.

[0014] The invention also relates to a method for producing a busbar according to any one of claims 1-9. The method comprises the following steps: Providing a base body made of a flat material made of aluminum or an aluminum alloy, Providing a connecting part made of a flat material, Connecting the base body to the connecting part using a melting joining process and creating a mixed structure of the materials of the base body and the connecting part, wherein the mixed structure extends in a contact surface plane perpendicular to the thickness of the connecting area over a surface portion of at least 50%, preferably at least 75%, of the contact area associated with the contact surface plane. This provides a sufficient interface cross-section consisting of a mixed structure for current transfer. Due to the selected joining process, pre-diffusion of the materials already occurs.

[0015] Laser welding, preferably vacuum laser welding, can be used as the melting joining process. Laser welding allows for the targeted introduction of the desired amount of heat. Furthermore, it is a sufficiently well-known and developed technology for generating such localized heating. Vacuum laser welding, in particular, has proven to be very effective for this application.

[0016] Advantageously, laser welding can be performed from the section of the base body that overlaps the connecting part, penetrating this section of the base part, and into the connecting part. This completely melts the base part in this section, but the penetration depth into the connecting part can be precisely adjusted.

[0017] According to a method variant, it is provided that the laser welding is carried out in such a way that the mixed structure has a maximum extension in the thickness direction of the connecting part which is less than 50%, preferably less than 25%, of the thickness of the connecting part.

[0018] Preferably, the connecting part can be inserted or pressed into a recess of the base body, wherein the recess has a stepped shape and enables a flush installation of the connecting part.

[0019] Embodiments of the present invention are explained in more detail below with reference to the drawings. They show: Fig. 1 a first embodiment of a busbar in a perspective top view, Fig. 2 an enlarged cross-sectional view of the connection area of ​​the busbar Fig. 1, Fig. 3 a second embodiment of a busbar in a perspective top view, and Fig. 4 an enlarged cross-sectional view of the connection area of ​​the busbar Fig. 3.

[0020] In Fig. 1 shows a busbar 1, which is used to connect electrical components, including other busbars (not shown). The busbar 1 has a three-dimensional profile in space to bridge both vertical and horizontal distances. The busbar 1 provides a stable, self-supporting body that retains its shape under normal operating conditions and generally has at least two connection areas for connecting to electronic components or other busbars. One of these connection areas 2 is in Fig. 1 shown.

[0021] In addition to the connection area 2, the busbar 1 has a base body 3 formed from a sheet metal strip, which has a rectangular cross-section. The base body 3 is made of an aluminum alloy and, in the illustrated embodiment, has a horizontal bend 4 of 90° and two vertical movements 5 and 6 of 90° each. A connecting part 7 made of a copper alloy is provided in the connection area 2. The connecting part 7 is punched from a sheet metal material and thus has a uniform thickness D. A The base body 3 also has a nearly uniform thickness D B on.

[0022] The connecting part 7 is provided with a circular connection opening 8 and is provided with a corresponding circular rounded portion at its front end 9. The rear end 10 facing the base body 3 is formed in a straight line. The connecting section 11 of the base body 3 facing the connecting part 7 is formed in a straight line and has a stepped recess 12. The recess 12 extends in a straight line from the first side edge 13 to the second side edge 14 of the base body 3 and has a uniform width B and a likewise uniform depth T. In the present case, the depth T is essentially 0.5 times the thickness D. B . The thickness D A of the connecting part 7 corresponds to 0.7 times the thickness D B of the base body 3 (thus lies in the range of 0.5 - 0.9 times the thickness D B). Due to the selected proportions, the connecting part 7 projects beyond the adjacent connecting surface 15 of the base body 3. In the present case, the connecting part 7 therefore projects by almost 0.3 times its thickness D A via the connection side 15 of the base body 3.

[0023] The width B A of the connecting part 7 is slightly larger than the width B Bof the base body 3 and protrudes evenly over both side edges 13 and 14. The connecting part 7 is precisely fitted into the stepped recess 12 and is overlapped by the base body 3 on its upper side 16 by the width B of the recess 12. The corresponding contact surface 17 of the recess 12 is connected to the upper side 16 of the connecting piece 7 by means of a vacuum laser welding process. As a result, a mixed structure 18 is formed in the area of ​​the contact surface 17, which is symbolically indicated by a thicker line. This is a time-stable mixed phase between the copper alloy of the connecting part 7 and the aluminum alloy of the base body 3. The weld seam is set such that the mixed structure 18 is in the contact surface plane E K extends over a portion of the contact surface 17 that is greater than 75%. As a result, the majority of the contact surface plane E Kthe mixed structure. The laser welding is carried out from the upper side of the base body 3 facing away from the connection side 15, so that the base body 3 is melted over the entire thickness of its area overlapping the connection part 7. The weld seam thus extends over the entire width B B of the base body 3 and forms in the area of ​​the contact surface plane E K a width B M of the mixed structure, which corresponds to 0.9 times the width B of the recess 12.

[0024] In the following, the effect and function of the above embodiment as well as the production of the busbar 1 are explained in more detail.

[0025] By means of the connection area 2, the busbar 1 is connected to an electrical component (e.g., another busbar) using corresponding connection elements passed through the connection opening 8. The opposite end of the busbar 1 (not shown) is designed accordingly. Due to the protrusion of the connection part 7, only the copper material comes into contact with the connection surface of the electrical component, whereas a suitable distance remains from the base body 3. The mixed structure 18 essentially anticipates diffusion at the contact surface 17, which would otherwise occur between the two material partners. This counteracts a deterioration in the contact resistance in this area, which could occur with increasing service life of the busbar 1. The two workpieces form an intermetallic compound of the otherwise insoluble metals.In addition, the formation of foreign layers (e.g. oxides) in the area of ​​the contact surface 17 is prevented.

[0026] A method for producing the busbar 1 comprises the following steps: Providing a base body 3 made of a flat material made of an aluminum alloy, Providing a connecting part 7 made of a flat material, made of a copper alloy, Connecting the base body 3 to the connecting part 7 by means of a vacuum laser welding process, in which the mixed structure 18 of the materials of the base body 3 and the connecting part 7 is formed with corresponding expansion. In the vacuum laser welding process, only the overlapping area of ​​the base body 3 is completely melted in its thickness, whereas the penetration depth and melting into the copper material of the connecting part 7 only occurs to a certain depth, which is a maximum of 0.25 times the thickness D AAs a result, the weld seam on the connection side 19 of the connection part 7 is not visible and a flat connection side 19 is formed.

[0027] In the following, the Fig. 3 and Fig. 4, a second embodiment of a busbar 1 according to the invention is explained in more detail. Only the essential differences from the previous embodiment will be discussed below. Therefore, the same reference numerals are used for identical and functionally equivalent components of the busbar 1, and reference is made to the above discussion.

[0028] The base body 3 is provided in the connection area 2 with an expanded connecting section 11, which adjoins the vertical bend 6. The connecting section 11 is provided with a circular opening 20, into which an annular recess 12 is formed. This configuration causes the opening 20 to widen in a stepwise manner toward the connection side 15. The connecting part 7 is annular and has been pressed into the recess 12. In the illustrated embodiment, the depth T corresponds approximately to 0.75 times the thickness D. B of the base body 3. The thickness D A In the present embodiment, this corresponds to approximately 0.85 times the thickness D B of the base body 3. Accordingly, the connecting part 7 protrudes from the recess 12, so that only contact with the connection side 19 of the connecting part 7 is guaranteed.

[0029] Due to the annular overlap of the base body 3 and the connecting part 7, the width B of the recess can be smaller. The width B M of the formed mixed structure 18 in the area of ​​the contact surface plane E K is again approximately 0.9 times the width B. The vacuum laser welding is again performed from the top side 16 of the connecting section 11, so that the entire overlap area of ​​the base body 3 is penetrated and only a certain depth of the connecting part 7 is melted. The welding is performed circumferentially without a gap.

[0030] Due to the inventive design of the busbar 1, the use of an aluminum alloy is also possible for high-current applications. Aluminum alloys offer the advantage of enabling significant weight reduction and being more cost-effective. Due to the solid connection between the connecting part 7 made of the copper alloy and the base body 7 made of an aluminum alloy, no additional components are required. The weld seam creates a time-stable mixed structure (mixed phase) between copper and aluminum. List of reference symbols 1 busbar 2 Connection area 3 base bodies 4 Horizontal bending 5 Vertical bending 6 Vertical bending 7 Connection part 8 Connection opening 9 Front end 10 Rear end 11 connecting section 12 recess 13 Side edge 14 Side edge 15 Connection side 16 Top 17 Contact surface 18 mixed structures 19 Connection side 20 Opening D A Thickness of connecting part D B Thickness of base part B A Width of connecting part B Width recess T Depth recess E K Contact surface level B B Wide base body B M Wide mixed structures

Claims

[1] Busbar (1), in particular for high-current applications, with a base body (3) made of aluminium or an aluminium alloy and a connection area (2) for connecting to other electrical components, characterized by that the section of the base body (3) assigned to the connection area (2) has a thickness (D B ) of the base body (3) has a recess (12) reducing the thickness of the connecting part (7) made of copper or a copper alloy, and in that the base body (3) and the connecting part (7) are connected to one another by means of a melting joining process at at least one contact surface (17) of the recess (12) in such a way that a mixed structure of the materials of the base body (3) and the connecting part (7) is present in this region. [2] Busbar (1) according to claim 1, characterized bythat the recess (12) has a step shape such that a connecting section of the connecting part (7) essentially fills the step shape and is covered in an overlapping manner by a section of the base body (3) on the side of the base body (3) facing away from a connection side (15). [3] Busbar (1) according to claim 1 or 2, characterized by that the connecting part (7) is designed as a flat part having a thickness (D A ) which is greater than the depth (T) of the recess (12). [4] Busbar (1) according to one of claims 1-3, characterized by that the thickness (D A ) of the connecting part (7) is 0.5 - 0.9 times, preferably 0.65 - 0.8 times, the thickness (D B ) of the section of the base body (3) assigned to the connection area (2). [5] Busbar (1) according to one of claims 1-4, characterized by that the connecting part (7), preferably with 0.1 - 0.3 times its thickness (D A), protrudes beyond the connection side (15) of the base body (3). [6] Busbar (1) according to one of claims 2-5, characterized by that the contact surface (17) of the recess (12) has a width (B) and that the area with the mixed structure (18) is in the contact surface plane (E K ) over a width (B M ) which corresponds to at least 0.5 times, preferably at least 0.7 times, the width (B) of the recess (12). [7] Busbar (1) according to one of claims 1-6, characterized by that the connection of the base body (3) and the connecting part (7) is effected by means of the melting joining process through the overlapping section of the base body (3). [8] Busbar (1) according to one of claims 1-7, characterized by that the connecting part (7) is designed as a stepped extension of the base body (3). [9] Busbar (1) according to one of claims 1-7, characterized bythat the connecting part (7) is designed as a disc-shaped insert part which is inserted into a recess (12) which is closed at the circumference. [10] Busbar arrangement with a busbar (1) according to one of claims 1-9 and an electrical component connected to this busbar (1), characterized by that a distance remains between the connected electrical component and the section of the base body (3) assigned to the connection area (2) and direct contact between the busbar (1) and the electrical component is only provided by means of the connection part (7). [11] Method for producing a busbar (1) according to one of claims 1-9, comprising the following steps: Providing a base body (3) made of a flat material made of aluminum or an aluminum alloy, Providing a connecting part (7) made of a flat material made of copper or a copper alloy, Connecting the base body (3) to the connecting part (7) by means of a melting joining process and producing a mixed structure (18) of the materials of the base body (3) and the connecting part (7), wherein the mixed structure (18) is in a contact surface plane (E K ) perpendicular to the thickness of the connection area (2) over a surface portion of the contact surface plane (E K ) associated contact surface (17) of at least 50%, preferably at least 75%. [12] Method according to claim 11, characterized by that laser welding, preferably vacuum laser welding, is used as the melting joining process. [13] Method according to claim 12, characterized by that the laser welding is carried out from the section of the base body (3) overlapping the connecting part (7), penetrates this section of the base part (3) and into the connecting part (7). [14] Method according to claim 13, characterized bythat the laser welding is carried out in such a way that the mixed structure (18) has a maximum extension in the thickness direction of the connecting part (7) which is less than 50%, preferably less than 25%, of the thickness (D A ) of the connecting part (7). [15] Method according to one of claims 11-14, characterized by that the connecting part (7) is inserted or pressed into a recess (12) of the base body (3), wherein the recess (12) has a stepped shape and enables a flush installation of the connecting part (7).

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