A method of processing a busbar and a busbar formed thereby

Abstract

A method of processing a power busbar to form a flexible region and a power busbar formed thereby. In accordance with the method, a power busbar is provided having first and second portions. The second portion of the power busbar is annealed to make the second portion more flexible. The annealing includes applying an electromagnetic field to the second portion for a brief period of time to generate eddy currents in the second portion, thereby heating the second portion. The first portion of the power busbar is cooled during the application of the electromagnetic field to the second portion of the power busbar. The cooling of the first portion helps prevent the first portion from being annealed by the electromagnetic field, thereby making the first portion less flexible than the second portion.

Description

ENNOV-006-PCTA METHOD OF PROCESSING A BUSBAR AND A BUSBAR FORMED THEREBYCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of priority under 35 U. S. C. § 119(e) to U. S. Provisional Patent Application No.: 63 / 769,449 filed on 10 March 2025, which is herein incorporated by reference.TECHNICAL FIELD

[0002] This disclosure relates generally to bus bars for conveying electrical power.BACKGROUND

[0003] Bus bars are commonly used to provide power to electrical and electronic devices and components, such as batteries, terminals, electric motors, etc.Conventionally, a bus bar includes a conductor, such as a bar or a plate composed of a conductive metal, such as copper or aluminum, and is relatively thick to better conduct electric current. Due to the composition, thickness and configuration of a busbar, the busbar is typically rigid and difficult to configure, position and make electrical connections thereto. This becomes problematic in some applications where space is limited and the busbar needs to be configured while being installed in place. Thus, it would be desirable to provide a busbar that is more easily configurable.SUMMARY

[0004] Disclosed herein is a method of processing a power busbar to form a flexible region. In accordance with the method, a power busbar is provided having a first portion and a second portion. The second portion of the power busbar is annealed to make the second portion more flexible. The annealing includes applying an electromagnetic field to the second portion for a brief heating period of time to generate eddy currents in the second portion, thereby heating the second portion. The first portion of the power busbar is cooled during the application of the electromagnetic field to the second portion of the power busbar. The cooling of the first portion of the power busbar helps prevent the first portion from being annealed by the electromagnetic field, thereby making theENNOV-006-PCTfirst portion of the power busbar less flexible than the second portion of the power busbar.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

[0006] Fig. 1 is a perspective view of a busbar that may be selectively annealed using a method of this disclosure;

[0007] Fig. 2 is a perspective view of an annealing assembly having an annealing device and a holding assembly, the holding assembly being in a first configuration and supporting the busbar;

[0008] Fig. 3 is a perspective view of the annealing assembly with the holding assembly being in a second configuration and holding the busbar;

[0009] Fig. 4 is a perspective view of a portion of the holding assembly with the busbar inserted into a housing of the annealing device; and

[0010] Fig. 5 is a partial interior perspective view of the busbar inside the housing with the busbar being disposed between turns of an electromagnetic coil.DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0011] A method and apparatus are provided for processing a busbar to, inter alia, selectively soften one or more portions of the busbar so the busbar can be facilely bent (such as by hand) to change its configuration. The busbar may be for use in a device or a vehicle to convey power between different components or devices. For example, the busbar may be used in an electric vehicle (EV) to: convey power from a charging interface to an on-board charger, interconnect battery cells and / or battery modules, convey power to and from one or more inverters, and convey power to one or more motors. Only one or more selected portions of the busbar is / are softened so that remaining portion(s) retain their original hardness and strength. The selective softening is performed using local or zone induction annealing through the application of an electromagnetic field for a brief period of time, followed by cooling.ENNOV-006-PCT

[0012] A busbar may be formed by stamping a unitary metal conductor to have a configuration with different portions. The metal conductor may comprise copper, a copper alloy, aluminum or an aluminum alloy. In some embodiments, the metal conductor may have a thickness of 2-10 mm, a width of 10-50 mm and a length of 100 mm or greater. The metal conductor may have an ampacity of about 5 amps per square millimeter (5 A / mm2). The metal conductor may be stamped to form a busbar have openings formed therein, such as bolt and terminal holes, and may also be thinned in some portions. An example of a busbar that may be selectively softened is shown in the drawings and is designated by the reference numeral 10. Of course, other busbars with different configurations may be selectively softened as well.

[0013] The busbar 10 may have a first portion 12 that is not to be annealed and is to be cooled so that it retains its metallurgical hardness; a second portion 14 that is to be annealed to increase its softness and, thus, flexibility; and a third portion 16 that is not to be annealed, but is not actively cooled. The first portion 12 may comprise a plurality of ring terminals 18 for connection to a first device, and the third portion 16 may comprise a header 20. As shown, the ring terminals 18 have openings for receiving bolts or other fasteners that may secure wire terminals to the busbar 10. The second portion 14 may comprise a plurality of arms 22 separated by spaces or windows for connecting the first portion 12 to the third portion 16. The busbar 10 is formed from a conductive metal, such as copper, a copper alloy or aluminum. The ring terminals 18 may be plated with nickel. In some embodiments, the busbar 10 may be formed from annealed copper having a temper of " Annealed to Temper - 1 / 2 hard" (ASTM Designation: B 601-02, designation code 082), which is annealed copper that is typically used in electrical applications.

[0014] The O series of designations in ASTM Designation: B 601-02 (hereinafter " ASTM-B601-02") are for copper annealed to meet specific mechanical properties. These mechanical properties include strength, hardness, ductility and formability.Strength is the ability of the copper to withstand applied forces without failing; hardness is the copper's ability to resist surface indentation or scratching; ductility is the ability of the copper to deform under tensile stress without breaking; and formability (which is related to ductility) is how easily the copper can be shaped through processes likeENNOV-006-PCTbending and stamping. Typically, hardness and strength are related and ductility and formability are related. The O series designations include codes: 070 (Dead Soft Anneal), 080 (Annealed to Temper - 1 / 8 hard), 081 (Annealed to Temper - 1 / 4 hard) and 082 (Annealed to Temper - 1 / 2 hard). Within the group 070, 080, 081 and 082, the 070 copper has the lowest strength and hardness and the highest ductility and formability, while the 082 copper has the highest strength and hardness and the lowest ductility and formability, with the 080 copper and the 081 copper being intermediate the 070 copper and the 082 copper in these properties. The 081 copper has lower strength and hardness, but is more ductile and formable than the 082 copper, while the 080 copper has lower strength and hardness, but is more ductile and formable than the 081 copper. In other words, the 080 copper is softer and more malleable than the 081 copper, which is softer and more malleable than the 082 copper.

[0015] Referring now to Figs. 2-5, there is shown an annealing assembly 40 that includes an annealing device 30 and a holding assembly 36. The annealing device 30 is configured to zone anneal the busbar 10. The annealing device 30 includes a housing 32 enclosing a high-frequency electromagnetic coil 34 (best shown in Fig. 5). The coil 34 may comprise copper or a copper alloy and is configured to conform to the shape of the second portion 14 of the busbar 10, i.e. to surround or mostly surround the second portion 14. For example, the coil 34 may be configured to have upper and lower turns (loops), between which the second portion 14 may be inserted such that the second portion 14 is sandwiched between the upper and lower turns, as is described below and shown in Fig. 5. In another embodiment, by way of example, the coil 34 may be helical and form a cylindrical interior that receives a second portion of a busbar to be annealed, which may or may not be cylindrical. In these embodiments, the coil 34 would circumferentially surround the second portion of the power busbar.

[0016] The coil 34 is disposed in a chamber 35 of the housing 32 such that there is a space below the coil 34 for receiving a portion of a holding assembly 36 holding the busbar 10. Leads 38 of the coil 34 extend from the housing 32 and are connected to a high frequency AC power source. The AC power source is configured to provide power in a range of from about 1 kW to about 5 kW and a frequency range of from about 20 kHz to about 500 kHz. When power is provided to the coil 34, an electromagnetic field isENNOV-006-PCTgenerated for application to a portion of the busbar 10, such as the second portion 14. The housing 32 has an enlarged opening, through which the holding assembly 36 with the busbar 10 may be inserted. The housing 32 may be formed from ceramic or a high temperature plastic, such as an aromatic polyamide or polyphenylene sulfide.

[0017] The holding assembly 36 is configured to hold the busbar 10 in the housing 32 during the application of the electromagnetic field to the power busbar 10. The holding assembly 36 includes a first holding block 42, a second holding block 44, a first base block 46 and a second base block 48. The first holding block 42 may be formed from a machinable ceramic and has a body with a plurality of holding projections 52 extending therefrom. The second holding block 44 may also be formed from a machinable ceramic. The second holding block 44 has a body with a plurality of recesses or nooks 58 formed therein. The nooks 58 are configured to receive the projections 52 of the first holding block 42, as well as the ring terminals 18 of the first portion 12 of the busbar 10. Since the first and second holding blocks 42, 44 are formed from ceramic, they do not heat up when the electromagnetic field is generated by the coil 34.

[0018] A bore 60 extends through an end of the body of the first holding block 42 and into an end one of the nooks 58. A first end portion of a tube 62 is disposed in the bore 60. The tube 62 may be formed from ceramic or high temperature plastic. A second end of the tube 62 is connected to a source of cooling gas, such as a mixture of nitrogen gas (N2) and hydrogen gas (H2). In some embodiments, a gas mixture comprising 5% H2and 95% N2may be used as a cooling gas. Although not shown, the nooks 58 may be connected together such that cooling gas delivered to the end one of the nooks 58 through the tube 62 may travel to the other nooks 58. The first holding block 42 is secured to the first base block 46, such as by bolts, and the second holding block 44 is secured to the second base block 48, such as by bolts. The first base block 46 and the second base block 48 each have a narrow portion for insertion into the housing 32. The first and second base blocks 46, 48 may be formed from ceramic or a high temperature plastic, such as an aromatic polyamide or polyphenylene sulfide.

[0019] The first base block 46 and the second base block 48 are each movable in an X-direction, such as by a linear drive. One or both of the first base block 46 and theENNOV-006-PCTsecond base block 46 are also movable in a Z-direction, toward and away from each other, such as by another linear drive. Since the first and second holding blocks 42, 44 are secured to the first and second base blocks 46, 48, the first and second holding blocks 42, 44 are movable with the first and second base blocks 46, 48. The moveable nature of the first and second base blocks 46, 48 allows the configuration of the holding assembly 36 to be changed. As shown In Fig. 2, the holding assembly 36 is in a first configuration, positioned in a first location outside the housing 32. When the holding assembly 36 is in the first configuration, the first and second holding blocks 42, 44 are spaced apart.

[0020] The busbar 10 is mounted to the holding assembly 36 by first positioning the busbar 10 relative to the holding assembly 36 when the holding assembly 36 is in the first configuration. As shown in Fig. 2., the ring terminals 18 are disposed in the nooks 58 of the second holding block 44, respectively, and the header 20 is supported on the narrow portion of the second base block 48. The first and second base blocks 46, 48 are then moved together to place the holding assembly 36 in a second configuration, wherein the first and second holding blocks 42, 44 engage each other. The movement of the first and second base blocks 46, 48 together causes the projections 52 of the first holding block 42 to move into the nooks 58 of the second holding block 44, respectively, as shown in Fig. 3. Thus, when the holding assembly 36 is in the second configuration, the ring terminals 18 are securely held in the nooks 58 and are disposed between the first and second holding blocks 42, 44.

[0021] With the busbar 10 mounted to the holding assembly 36, as described above, the narrow portions of the first and second base blocks 46, 48 are then moved in the X-direction to insert the busbar 10 into the chamber 35 of the housing 32, as shown in Figs. 4-5. The busbar 10 is inserted into the chamber 35 of the housing 32 such that the second portion 14 (arms 22) of the busbar 10 is / are disposed between upper and lower turns 34a, b of the coil 34, as shown in Fig. 5. With the busbar 10 so positioned in the chamber 35, cooling gas is supplied to the nooks 58 through the tube 62. The coil 34 is then briefly provided with power to generate the electromagnetic field and thereby induce eddy currents at the surface of the busbar 10 in the second portion 14 to quickly create a penetrating zone of very high temperatures—red hot in seconds. TheENNOV-006-PCTelectromagnetic field may be applied to the second portion 14 of the power busbar 10 for a heating period of time in a range of from about 1 second to about 15 seconds, more typically in a range of from about 2 seconds to about 10 seconds. This brief application of the electromagnetic field heats the second portion 14 to a temperature in a range of from about 500°F to about 1200°F, more usually, in a range from about 600 °F to about 800°F. Because it happens fast, the portions outside the second portion 14 do not get hot enough to anneal. Moreover, the first portion 12 is cooled by the cooling gas to lower its temperature to preserve its metallurgical strength and hardness.

[0022] The application of the cooling gas to the first portion 12 also helps prevent discoloration or oxidation of the first portion 12, particularly in those embodiments where the first portion 12 is plated with nickel. In some embodiments, the flow rate of the cooling gas may be selected to be at the lowest value that prevents discoloration of the first portion 12.

[0023] After the second portion 14 of the busbar 10 is heated for the heating period of time by the coil 34, the coil 34 is de-energized (disconnected from the AC power source) and the second portion 14 is allowed to cool naturally to ambient temperature, thereby annealing the second portion 14. This (zone) annealing of the second portion 14 (arms 22) of the busbar 10 significantly improves its ductility and reduces its hardness, making it easier to bend and otherwise reconfigure. This increase in ductility and softness allows the second portion 14 (arms 22) to be reshaped to facilitate the proper positioning of the first portion 12 (ring terminals 18) relative to the third portion 16 (header 20). Such reshaping may be performed by hand of a user to make it easier to position bolting patterns in large assemblies where tolerance stacks can cause significant misalignment. While the second portion 14 is deformable (bendable), the first portion 12 and the third portion 16 are not deformable.

[0024] The zone annealing of the second portion 14 of the busbar 10 also improves its conductivity and helps eliminate internal stresses and defects in the metal (e.g. copper), thereby reducing resistance when current flows therethrough.

[0025] In the embodiments where the busbar 10 is initially formed from copper having an ASTM-B601-02 temper code 082, the second portion 14 of the busbar 10 may be annealed by the energization of the coil 34 to have a temper in a range of fromENNOV-006-PCTASTM-B601-02 temper code 81 to ASTM-B601-02 temper code 80. This change in temper changes the ductility of the second portion 14 of the busbar 10 enough to permit a human to manually change the configuration of the second portion 14 and, thus, the overall configuration of the busbar 10.

[0026] It should be appreciated that in other embodiments, the holding assembly 36 may be configured to have a third holding block that helps form a holding chamber within which at least a part of the third portion 16 of the busbar 10 is disposed. This third holding block may be formed from ceramic and may be secured to the second base block 48. The holding chamber may be provided with the cooling gas through another tube connected to the source of the cooling gas. In this manner, the third portion 16 of the power busbar 10 may also be actively cooled during the heating of the second portion 14 of the power busbar 10 by the coil 34.

[0027] It should further be appreciated that in other embodiments, busbars of different sizes and configurations (e.g. cylindrical, rectangular, etc.) may be selectively annealed to have one or more flexible portions. For example, a rectangular busbar having a thickness of 2-10 mm, more particularly 2-6 mm, a width of 10-50 mm, more particularly 10-30 mm and a length of greater than 100 mm may divided into five or more portions, wherein the portions include target portions and non-target portions, with the portions alternating between a non-target portion and a target portion. The target portions of the rectangular busbar may be zone annealed using electromagnetic field(s) and the non-target zones may be cooled with cooling fluid, all in accordance with the methods described herein, such that the rectangular busbar has alternating flexible portions and non-flexible portions. In some embodiments, end portions of the rectangular busbar may be non-flexible; in other embodiments, end portions of the rectangular busbar may be flexible; and in still other embodiments, one end portion of the rectangular busbar may be flexible and the other end portion may be non-flexible. One or both of the end portions may have holes formed therein to permit the mounting of the zone annealed bus bar to other devices or conductors. After the zone annealing, the rectangular busbar may then be manually manipulated by a human user to form bends in one or more of the flexible portions. The rectangular busbar may be manuallyENNOV-006-PCTmanipulated to have a undulating configuration, a channel-shaped configuration, a zigzag or dogleg configuration or other desired configuration.

[0028] It is to be understood that the description of the foregoing exemplary embodiment(s) is (are) intended to be only illustrative, rather than exhaustive. Those of ordinary skill will be able to make certain additions, deletions, and / or modifications to the embodiment(s) of the disclosed subject matter without departing from the spirit of the disclosure or its scope.

Claims

ENNOV-006-PCTWhat is claimed is:

1. A method of processing a power busbar to form a flexible region, the method comprising:providing a power busbar having a first portion and a second portion; annealing the second portion of the power busbar to make the second portion more flexible, the annealing comprising applying an electromagnetic field to the second portion for a brief heating period of time to generate eddy currents in the second portion, thereby heating the second portion;cooling the first portion of the power busbar during the application of the electromagnetic field to the second portion of the power busbar; andwherein the cooling of the first portion of the power busbar helps prevent the first portion from being annealed by the electromagnetic field, thereby making the first portion of the power busbar less flexible than the second portion of the power busbar.

2. The method of claim 1, wherein the power busbar further comprises a third portion, and wherein the applying of the electromagnetic field to the second portion of the power busbar is performed such that eddy currents are not generated in the third portion of the power busbar and, thus, the third portion is not annealed, thereby making the third portion of the power busbar less flexible than the second portion of the busbar.

3. The method of claim 2, wherein the second portion of the power busbar is disposed between the first portion of the power busbar and the third portion of the power busbar, thereby providing the power busbar with a flexible region disposed between two relatively rigid regions.

4. The method of claim 1, wherein the applying the electromagnetic field to the second portion of the power busbar comprises placing a conductive coil adjacent to the second portion of the power busbar and supplying the conductive coil with high frequency AC power to the coil for the brief heating period of time.ENNOV-006-PCT5. The method of claim 4, wherein the brief heating period of time is from about 1 second to about 15 seconds.

6. The method of claim 5, wherein the brief heating period of time is from about 2 seconds to about 10 seconds.

7. The method of claim 5, wherein the high frequency AC power is in a power range of from about 1 kW to about 5 kW and a frequency range from about 20 kHz to about 500 kHz.

8. The method of claim 1, wherein the first portion of the power busbar is cooled by a cooling fluid.

9. The method of claim 8, wherein the cooling fluid comprises a cooling gas, and wherein the application of the electromagnetic field to the second portion of the power busbar and the cooling of the first portion of the power busbar is performed inside a housing.

10. The method of claim 9, wherein the cooling gas is a gas mixture comprising nitrogen (N₂) gas and hydrogen (H₂) gas.

11. The method of claim 10, wherein the gas mixture comprises about 5% hydrogen and about 95% nitrogen.

12. The method of claim 9, comprising holding the power busbar with a holding assembly inside the housing during the application of the electromagnetic field to the second portion of the power busbar, the holding assembly comprising a structure and a first block having one or more recesses within which the first portion of the power busbar is disposed; andmoving the structure to cover at least part of the first portion of the power busbar; andENNOV-006-PCTsupplying the cooling fluid to the one or more recesses in the block to cool the first portion of the power busbar.

13. The method of claim 12, wherein the structure comprises a plurality of projections extending from a second block, the first block comprises a plurality of recesses and the first portion of the power busbar comprises a plurality of pieces; and wherein the holding the power busbar comprises holding the pieces of the first portion of the power busbar in the recesses, respectively; andwherein the moving the structure comprises moving the second block to move the projections into the recesses and to press against the pieces of the first portion of the power busbar.

14. The method of claim 13, wherein the block and the structure are each formed from ceramic.

15. The method of claim 12, comprising:allowing the power busbar to cool to ambient temperature after the application of the electromagnetic field;removing the power busbar from the housing and the holding assembly; and using a human force to bend the second portion of the power busbar.

16. A power busbar formed from copper or a copper alloy and comprising:a first portion annealed to have a first temper and a second portion annealed to have a second temper, with the first temper being different than the second temper such that the second portion is softer and more malleable than the first portion; and wherein the second portion is manually bendable, while the first portion is not manually bendable.

17. The power busbar of claim 16, wherein the first portion has a hole extending therethrough and is plated with nickel that is not oxidized.ENNOV-006-PCT18. The power busbar of claim 16, wherein the first temper of the first portion is ASTM-B601-02 temper code O82, and the second temper of the second portion is in a range of from ASTM-B601-02 temper code 81 to ASTM-B601-02 temper code 80.

19. The power busbar of claim 16, further comprising a third portion annealed to have a third temper, which is different than the second temper such that the second portion is softer and more malleable than the third portion; andwherein the second portion is disposed between the first portion and the third portion.

20. The power busbar of claim 19, wherein the first temper of the first portion and the third temper of the third portion are each ASTM-B601-02 temper code O82, and the second temper of the second portion is in a range of from ASTM-B601-02 temper code 81 to ASTM-B601-02 temper code 80.

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