Connection structure, busbar and connector

Abstract

The present application provides a connection structure, bus bar and connector. The connection structure can connect bus bars and connection objects each having a base material made of aluminum to each other by bolt fastening, and can maintain low contact resistance. A first bus bar (bus bar) (11) has a first base material (12) made of aluminum and a copper sheet (13) that is metal-bonded to the first base material and forms a first connection surface (S1), a second bus bar (connection object) (21) has a second base material (22) made of aluminum, a second connection surface (S2) is formed by the second base material (22), the connection structure includes: a potting material (15) coated between the first connection surface and the second connection surface; and a bolt (31) that fastens the first bus bar and the second bus bar to each other in a manner that the first connection surface and the second connection surface press each other, the first connection surface has a protrusion that protrudes toward the second connection surface.

Description

Technical Field

[0001] This invention relates to a connection structure, and more particularly to a connection structure in which a busbar made of aluminum and a connecting object made of aluminum are connected to each other by bolt fastening.

[0002] Furthermore, the present invention also relates to a busbar for such a connection structure and a connector having a busbar. Background Technology

[0003] Generally, the electrical connection between the motor and inverter units in electric vehicles is achieved by bolting the motor-side busbar and the inverter-side busbar together. To suppress heat generation when current flows between the motor and inverter units, busbars made of copper with low contact resistance are typically used.

[0004] However, the busbars made of copper are heavy, and since they are relatively expensive, it is desirable to use aluminum, which is lightweight, has excellent conductivity, and is relatively inexpensive.

[0005] For example, in patent document 1, such as Figure 16 As shown, a connection structure is disclosed, which fastens a first busbar 1 containing aluminum as the main component and a second busbar 2 containing metal as the main component by bolts 3 and nuts 4.

[0006] Aluminum is known to readily react with oxygen. If an aluminum conductive component is exposed to outside air, the surface of the conductive component will be oxidized, forming an oxide film on the surface, which increases the contact resistance.

[0007] Therefore, in the connection structure of Patent Document 1, as Figure 17 As shown, a hemispherical or cylindrical protrusion 5 is formed on the surface of the first busbar 1 opposite to the second busbar 2. The configuration involves fastening the first busbar 1 and the second busbar 2 with bolts 3 and nuts 4, applying compressive force to the protrusion 5 in contact with the second busbar 2, causing plastic deformation of the protrusion 5, destroying the oxide coating 6 formed on the surface of the protrusion 5, and allowing the aluminum inside the protrusion 5 to directly contact the metal constituting the second busbar 2.

[0008] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2023-82637 According to the connection structure in Patent Document 1, by making the aluminum inside the protrusion 5 contact the second busbar 2, the contact resistance between the first busbar 1 and the second busbar 2 can be reduced.

[0009] However, when the second busbar 2 contains aluminum as the main component, since an oxide coating 6 is also formed on the surface of the second busbar 2, even if the oxide coating 6 on the surface of the protrusion 5 of the first busbar 1 is damaged, the aluminum inside the protrusion 5 may not directly contact the aluminum constituting the second busbar 2.

[0010] Furthermore, even if the aluminum inside the protrusion 5 of the first busbar 1 is in direct contact with the aluminum constituting the second busbar 2, if the connection structure of Patent Document 1 is left in the atmosphere for a long time, an oxide coating may form at the contact area between the first busbar 1 and the second busbar 2, resulting in increased contact resistance. Summary of the Invention

[0011] The present invention was made to solve such conventional problems, and its purpose is to provide a connection structure that can connect a busbar having a base material made of aluminum and a connected object to each other by bolt fastening, while maintaining low contact resistance.

[0012] Furthermore, the present invention also aims to provide a busbar for such a connection structure and a connector having the busbar.

[0013] The inventors of this invention Figure 1 The two flat busbars B1 and B2 were fastened together using bolt FB. The contact resistance of busbars B1 and B2 was measured by varying the tightening torque based on bolt FB. Furthermore, measurements were performed on busbars B1 and B2 in three scenarios: busbars both made of copper, busbars both made of aluminum, and busbars where one is made of copper and the other of aluminum.

[0014] The measurement results are shown in Figure 2 The curve graph. In Figure 2 In the figure, C1 represents the measurement result when both busbars B1 and B2 are made of copper, C2 represents the measurement result when both busbars B1 and B2 are made of aluminum, and C3 represents the measurement result when busbar B1 is made of copper and busbar B2 is made of aluminum.

[0015] In any of the measurement results C1 to C3, that is, regardless of the metal type of busbars B1 and B2, there is a tendency that the contact resistance decreases as the tightening torque increases.

[0016] As shown in the measurement result C1, if the busbars B1 and B2, both made of copper, are fastened together, even with a small tightening torque, the contact resistance is below 10μΩ, and there will be no problems such as temperature rise. A large current can flow between the busbars B1 and B2.

[0017] In contrast, as shown in measurement result C2, if busbars B1 and B2, both made of aluminum, are fastened together, the contact resistance remains high, approaching 100 μΩ, regardless of the tightening torque. This is presumably due to the strong oxide coating formed on the surfaces of the aluminum busbars B1 and B2. Therefore, when a large current flows between busbars B1 and B2, there are concerns about heat generation and temperature rise.

[0018] Therefore, when busbar B1, which is made of copper, and busbar B2, which is made of aluminum, are fastened together, as shown in the measurement result C3, it can be seen that although the contact resistance is several tens of μΩ when the fastening torque is small, if the fastening torque is increased, the contact resistance is less than 10 μΩ, just like when busbars B1 and B2 are both made of copper.

[0019] Furthermore, if the surface portion of the aluminum busbar B2, which is opposite to the copper busbar B1, is rubbed and scratched using a tool with sharp, pointed protrusions, and then the busbars B1 and B2 are fastened together, the contact resistance can be suppressed to a value lower than the measured result C3. Even with a small tightening torque, the contact resistance is below 10 μΩ.

[0020] Thus, if a combination of busbar B1 made of copper and busbar B2 made of aluminum is used, a low contact resistance of less than 10 μΩ can be obtained as an initial characteristic. However, if placed in a high-temperature environment of 150°C, the contact resistance exceeds 10 μΩ within 100 hours, indicating that countermeasures for environmental characteristics are needed.

[0021] The inventors conducted the above measurements and further, repeated, and in-depth research, resulting in the concept of using the surface of the copper sheet of a busbar with a plate-shaped copper sheet metally bonded to a first base material made of aluminum as the first connecting surface, and forming a protrusion on the first connecting surface. A second connecting surface is formed on a second base material made of aluminum for the object to be connected. A potting material is applied between the first and second connecting surfaces, and bolts are used to fasten the busbar and the object to be connected together by pressing the first and second connecting surfaces against each other. By concretizing this concept, the present invention described below was completed.

[0022] The connection structure involved in this invention is a connection structure that connects the first connecting surface of the busbar and the second connecting surface of the object to be connected, and the connection structure comprises: Encapsulating material is applied between the first and second connecting surfaces; and Bolts are used to fasten the busbar and the connected object together by pressing the first and second connecting surfaces together. The busbar has a first base material made of aluminum and a plate-shaped copper sheet that is metal-bonded to the first base material and forms a first connecting surface. The objects to be connected have a second base material made of aluminum, and the second connecting surface is formed from the second base material. The first connecting surface has a protrusion that extends toward the second connecting surface. When the busbar and the connected object are fastened together by bolts, the first and second connecting surfaces are covered with potting material, and the protrusions contact the second base material, and the first and second base materials are electrically connected to each other.

[0023] Preferably, the first connecting surface has an uneven shape portion that serves as a trace of the copper sheet being ultrasonically welded to the first base material, and the protrusion is formed by a portion of the uneven shape portion.

[0024] Furthermore, preferably, the bolt passes through a first through hole and a second through hole, the first through hole passing through the first connecting surface and penetrating the manifold, and the second through hole passing through the second connecting surface and penetrating the connected object.

[0025] The busbar involved in this invention is a busbar that is fastened to a connected object, and the busbar includes: The first base material is made of aluminum; and Metal bonded to a plate-shaped copper sheet of the first base material. The copper sheet has a first connecting surface that connects to the object being connected. The first connecting surface has a protrusion that extends toward the object being connected. When the busbar is fastened to the object to be connected, the protrusion on the first connecting surface contacts the object to be connected and is electrically connected to the object to be connected.

[0026] Preferably, the copper sheet is bonded to the first base material by ultrasonic welding.

[0027] Furthermore, preferably, the first connecting surface has an uneven shape portion that serves as a trace of the copper sheet being ultrasonically welded to the first base material, and the protrusion is formed by a portion of the uneven shape portion.

[0028] Furthermore, preferably, the busbar has a first through hole through which a bolt passing through the first connecting surface and used for fastening to the connected object passes.

[0029] The connector involved in this invention has the above-mentioned busbar.

[0030] Effects of the invention: According to the present invention, a potting material is applied between the first connecting surface of the busbar and the second connecting surface of the connected object. The busbar has a first base material made of aluminum and a plate-shaped copper sheet that is metal-bonded to the first base material and forms the first connecting surface. The connected object has a second base material made of aluminum, and the second connecting surface is formed by the second base material. When the busbar and the connected object are fastened together by bolts, the first and second connecting surfaces are covered by the potting material, and the protrusion of the first connecting surface protruding towards the second connecting surface contacts the second base material. The first and second base materials are electrically connected to each other. Therefore, the busbar and the connected object, which each have a base material made of aluminum, are connected together by bolts, and a low contact resistance can be maintained. Attached Figure Description

[0031] Figure 1 This is a photograph showing the measurement of the contact resistance of two busbars.

[0032] Figure 2 This is a graph showing the results of the contact resistance measurement.

[0033] Figure 3 This is a cross-sectional view illustrating the connection structure involved in an embodiment of the present invention.

[0034] Figure 4 This is an exploded view of the connection structure involved in the implementation method.

[0035] Figure 5 This is a partially enlarged cross-sectional view showing the first base material and copper sheet of the first busbar.

[0036] Figure 6 This is a perspective view showing the first base material positioned on an ultrasonic welding anvil and a fixing fixture during the fabrication of the first busbar.

[0037] Figure 7 This is a perspective view showing a copper sheet disposed on the surface of the first base material during the fabrication of the first busbar.

[0038] Figure 8 This is a perspective view showing the placement of an ultrasonic welding head on a copper sheet during the fabrication of the first busbar.

[0039] Figure 9 This is a three-dimensional view showing the welding surface of the welding head used for ultrasonic welding.

[0040] Figure 10 This is a perspective view showing a copper sheet ultrasonically welded to the surface of the first base material during the fabrication of the first busbar.

[0041] Figure 11 This is a partial three-dimensional view showing the surface of the copper sheet after ultrasonic welding.

[0042] Figure 12 This is a photograph showing a portion of the surface of a copper sheet after ultrasonic welding.

[0043] Figure 13 This is a perspective view showing the second busbar positioned on top of the first busbar.

[0044] Figure 14 It is a perspective view showing the first and second busbars after the bolts are tightened.

[0045] Figure 15 This is a perspective view showing the state in which the second busbars are bolted to the three first busbars of the connector.

[0046] Figure 16 This is a cross-sectional view showing the existing connection structure.

[0047] Figure 17 This is a partial cross-sectional view schematically showing the interface between the first busbar and the second busbar in an existing connection structure.

[0048] Figure Labels 1 First busbar, 2 Second busbar, 3 Bolt, 4 Nut, 5 Protrusion, 6 Oxide coating, 11 First busbar, 12 First base material, 12H, 13H Through holes, 13 Copper sheet, 13A Concave-convex shape, 13B Recess, 13C Protrusion, 14 First through hole, 15 Encapsulation material, 21 Second busbar, 22 Second base material, 23 Second through hole, 31 Bolt, 32 Nut, 41 Housing, 51 Anvil for ultrasonic welding, 52 Fixing clamp, 52A Cut-out, 53 Welding head for ultrasonic welding, 53A Welding surface, 53B Protrusion, B1, B2 Busbars, FB Bolt, C1, C2, C3 Measurement results, S1 First connecting surface, S2 Second connecting surface. Detailed Implementation

[0049] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0050] Figure 3 The diagram illustrates a connection structure according to an embodiment of the present invention. The connection structure includes a first busbar 11 and a second busbar 21 extending in a predetermined direction, and bolts 31 and nuts 32 fastening the first busbar 11 and the second busbar 21 together. The first busbar 11 constitutes the "busbar" of the present invention, and the second busbar 21 constitutes the "connection object" of the present invention.

[0051] For convenience, the direction in which the first busbar 11 and the second busbar 21 extend is called the Y direction, the direction in which the bolt 31 extends is called the Z direction, and the width direction of the first busbar 11 and the second busbar 21, which is orthogonal to both the Y and Z directions, is called the X direction.

[0052] like Figure 4 As shown, the first busbar 11 has a flat first base material 12 made of aluminum and a plate-shaped copper sheet 13 joined to the surface of the first base material 12 in the +Z direction. A through hole 12H is formed in the first base material 12, and a through hole 13H of the same size as the through hole 12H is formed in the copper sheet 13 in a manner coaxial with the through hole 12H in the first base material 12. Through these through holes 12H and 13H, a first through hole 14 is formed in the Z direction for the bolt 31 to pass through.

[0053] In addition, a first connecting surface S1 is formed by the surface of the copper sheet 13 in the +Z direction, and a potting material 15 is coated on the entire surface of the first connecting surface S1.

[0054] On the other hand, the second busbar 21 has a flat second base material 22 made of aluminum. A second through hole 23 is formed in the second busbar 21, which penetrates the second base material 22 in the Z direction for the bolt 31 to pass through.

[0055] Furthermore, a second connecting surface S2 is formed from the surface of the second base material 22 on the -Z direction side of the portion opposite to the first connecting surface S1 of the first busbar 11.

[0056] like Figure 5 As shown, the surface of the copper sheet 13 on the -Z direction side is bonded to the first base material 12 by a metal bonding. That is, at the interface between the first base material 12 and the copper sheet 13, the copper atoms constituting the copper sheet 13 are in a state of metal bonding with the aluminum atoms constituting the first base material 12, and there is no oxide coating between the first base material 12 and the copper sheet 13.

[0057] Furthermore, a concave-convex shape portion 13A is formed on the +Z direction side surface of the copper sheet 13 that forms the first connecting surface S1. The concave-convex shape portion 13A has a plurality of recesses 13B arranged in a row and a plurality of protrusions 13C disposed adjacent to the plurality of recesses 13B and protruding in the +Z direction respectively. The front end of the protrusion 13C has a sharp shape facing the +Z direction.

[0058] Generally, copper has a higher hardness than aluminum. When the first busbar 11 and the second busbar 21 are fastened together by pressing the first connecting surface S1 and the second connecting surface S2 against each other, the multiple protrusions 13C formed on the first connecting surface S1 break the oxide coating on the second connecting surface S2 of the second base material 22 formed in the second busbar 21 and come into direct contact with the second base material 22. If the fastening torque is increased, the multiple protrusions 13C not only break the oxide coating, but also bite into the interior of the second base material 22.

[0059] Next, the method for manufacturing the first busbar 11 of this structure will be explained.

[0060] like Figure 6 As shown, a fixing clamp 52 is disposed on the ultrasonic welding anvil 51. The fixing clamp 52 has a cutout 52A for receiving a flat first base material 12. The first base material 12 is received in the cutout 52A of the fixing clamp 52, thereby fixing it to the surface of the ultrasonic welding anvil 51 on the +Z direction side.

[0061] Next, as Figure 7 As shown, a copper sheet 13 is disposed on the surface of the first base material 12 in the +Z direction. At this time, the copper sheet 13 is disposed on the first base material 12 while being aligned with the first base material 12, with the through hole 13H of the copper sheet 13 located directly above the through hole 12H of the first base material 12.

[0062] Furthermore, such as Figure 8 As shown, an ultrasonic welding head 53 is disposed on the copper sheet 13. Figure 9 As shown, a planar welding surface 53A extending along the XY plane is formed on the -Z direction side end of the ultrasonic welding head 53. The welding surface 53A has a shape and size corresponding to the copper sheet 13, and a plurality of pyramidal protrusions 53B arranged in the X and Y directions and protruding in the -Z direction are formed on the welding surface 53A.

[0063] For example, multiple protrusions 53B are arranged at intervals of approximately 0.3 to 2.5 mm in the X and Y directions, respectively. Each protrusion 53B has a shape in which the four sides of a quadrangular pyramid stand upright at a 45-degree angle relative to the welding surface 53A, and has a height of 0.15 to 0.8 mm from the welding surface 53A in the -Z direction. However, these arrangement intervals, standing angles, and heights are merely examples and can be appropriately varied depending on the size of the copper sheet 13, etc.

[0064] With the welding surface 53A in contact with the copper sheet 13, ultrasonic vibration is applied to the ultrasonic welding head 53 while applying pressure in the -Z direction. The ultrasonic vibration applied to the ultrasonic welding head 53 is transmitted from the welding surface 53A of the ultrasonic welding head 53 to the copper sheet 13, propagates within the copper sheet 13, and generates friction between the -Z direction side surface of the copper sheet 13 and the +Z direction side surface of the first base material 12. As a result, the oxide coating formed on the surfaces of the contacting first base material 12 and the copper sheet 13 is destroyed, and the aluminum atoms constituting the first base material 12 and the copper atoms constituting the copper sheet 13 mix and form a metallic bond.

[0065] Simultaneously, through the ultrasonic vibration applied to the ultrasonic welding head 53, friction is also generated between the welding surface 53A of the ultrasonic welding head 53 and the surface of the copper sheet 13 in the +Z direction. Therefore, as... Figure 10 As shown, a concave-convex shape portion 13A is formed on the surface of the copper sheet 13 in the +Z direction. The concave-convex shape portion 13A is formed as a trace left when the copper sheet 13 is ultrasonically welded to the first base material 12. That is, multiple pyramidal-shaped protrusions 53B formed on the welding action surface 53A of the ultrasonic welding head 53 bite into the surface of the copper sheet 13, and the shape of the multiple protrusions 53B is transferred onto the copper sheet 13, such as... Figure 11 As shown, multiple pyramidal recesses 13B are formed on the surface of the copper sheet 13.

[0066] Furthermore, as part of the concave-convex shape portion 13A, a protrusion 13C is formed adjacent to each recess 13B and protrudes in the +Z direction. It can be considered that the protrusion 13C is formed by the copper bulge existing in the recess 13B when the recess 13B is formed by the protrusion 53B of the ultrasonic welding head 53.

[0067] Figure 12 A photograph is shown of the surface of the copper sheet 13 in the +Z direction after actual ultrasonic welding. It can be seen that protrusions 13C are formed adjacent to each recess 13B.

[0068] This completes the production of the first busbar 11.

[0069] When connecting the second busbar 21 to the first busbar 11, firstly, a potting material 15 is applied to the entire surface of the first connection surface S1 formed by the surface of the copper sheet 13 of the first busbar 11 in the +Z direction direction. Figure 13 As shown, while the second connecting surface S2 is in contact with the first connecting surface S1 via the potting material 15, the second busbar 21 is positioned on the +Z direction side of the first busbar 11.

[0070] In addition, the potting material 15 is used to protect the first connection surface S1 and the second connection surface S2 so that oxygen will not penetrate between the first connection surface S1 and the second connection surface S2 after the first busbar 11 and the second busbar 21 are connected. As the potting material 15, various general-purpose potting materials for the purpose of protecting and improving the durability of electronic components, such as epoxy resin, polyurethane, silicone, and acrylic, can be used.

[0071] After that, as Figure 14 As shown, by using bolts 31 and nuts 32 to fasten the first busbar 11 and the second busbar 21 together, the following is obtained: Figure 3 The connection structure is shown. Additionally, as... Figure 4 As shown, the bolt 31 passes through the second through hole 23 of the second base material 22 of the second busbar 21 and the first through hole 14 of the first busbar 11 in sequence, and is fastened by the nut 32.

[0072] Here, a plurality of protrusions 13C with sharp tips are formed on the +Z direction side of the copper sheet 13 that forms the first connecting surface S1 of the first busbar 11. Therefore, if the first busbar 11 and the second busbar 21 are fastened together with bolts 31 and nuts 32, the oxide coating on the second connecting surface S2 of the second base material 22 made of aluminum formed on the second busbar 21 is destroyed by the plurality of protrusions 13C of the first busbar 11, and the plurality of protrusions 13C come into direct contact with the second base material 22.

[0073] Furthermore, the surface of the copper sheet 13 on the -Z direction side is metal-bonded to the first base material 12 of the first busbar 11.

[0074] Therefore, the first base material 12 of the first busbar 11 is electrically connected to the second base material 22 of the second busbar 21 via the copper sheet 13.

[0075] That is, even if the first base material 12 of the first busbar 11 and the second base material 22 of the second busbar 21 are both made of aluminum, the first busbar 11 and the second busbar 21 can be connected to each other with low contact resistance.

[0076] Furthermore, since potting material 15 is applied between the first connecting surface S1 of the first busbar 11 and the second connecting surface S2 of the second busbar 21, the intrusion of oxygen into the first connecting surface S1 and the second connecting surface S2 is prevented by the potting material 15, thus maintaining a low contact resistance for a long time.

[0077] In addition, in the above embodiment, potting material 15 is applied to the first connecting surface S1 of the first busbar 11, but it is not limited to this. Instead of the first connecting surface S1, potting material 15 can be applied to the second connecting surface S2 of the second busbar 21, and the first busbar 11 and the second busbar 21 can be fastened together.

[0078] Figure 15 A connector with first busbars 11 is shown. The connector holds, for example, three first busbars 11 within a housing 41 formed of insulating material. Second busbars 21 can be fastened to the three first busbars 11 using bolts 31 and nuts 32 respectively. Furthermore, the first busbars 11 and second busbars 21 are fastened together after applying potting material 15 to the first connecting surface S1 of the first busbar 11 or the second connecting surface S2 of the second busbar 21.

[0079] In addition, the number of first busbars 11 is not limited to three.

[0080] Furthermore, the present invention is not limited to the connection between the first busbar 11 and the second busbar 21, and can also be applied to the following connection structure: a connection object such as a terminal having a second base material made of aluminum is used instead of the second busbar 21, and a busbar having a plate-shaped copper sheet metally bonded to a first base material made of aluminum, similar to the first busbar 11, is connected to the connection object.

Claims

1. A connection structure that connects a first connecting surface of a busbar and a second connecting surface of a connected object to each other, characterized in that, The connection structure includes: Encapsulating material is applied between the first connecting surface and the second connecting surface; and Bolts are used to fasten the busbar and the connected object together by pressing the first connecting surface and the second connecting surface against each other. The busbar has a first base material made of aluminum and a plate-shaped copper sheet that is metal-bonded to the first base material and forms the first connecting surface. The object to be connected has a second base material made of aluminum, and the second connecting surface is formed from the second base material. The first connecting surface has a protrusion that extends toward the second connecting surface. When the busbar and the connected object are fastened together by the bolts, the first connecting surface and the second connecting surface are covered by the potting material, and the protrusion contacts the second base material, and the first base material and the second base material are electrically connected to each other.

2. The connection structure according to claim 1, characterized in that, The first connecting surface has an uneven shape portion that serves as a trace left when the copper sheet is ultrasonically welded to the first base material, and the protrusion is formed by a portion of the uneven shape portion.

3. The connection structure according to claim 1, characterized in that, The bolt passes through a first through hole and a second through hole. The first through hole passes through the first connecting surface and through the busbar, and the second through hole passes through the second connecting surface and through the connected object.

4. A busbar, fastened to a connected object, characterized in that, The bus bar has the following features: The first base material is made of aluminum; and Metal bonded to a plate-shaped copper sheet of the first parent material. The copper sheet has a first connecting surface that connects to the object being connected. The first connecting surface has a protrusion that extends toward the object to be connected. When the busbar is fastened to the object to be connected, the protrusion on the first connecting surface contacts the object to be connected and is electrically connected to the object to be connected.

5. The busbar according to claim 4, characterized in that, The copper sheet is bonded to the first base material by ultrasonic welding, thus bonding it to the metal of the first base material.

6. The busbar according to claim 5, characterized in that, The first connecting surface has an uneven shape that serves as a trace left when the copper sheet is ultrasonically welded to the first base material. The protrusion is formed by a portion of the concave-convex shape.

7. The busbar according to claim 4, characterized in that, The busbar has a first through hole through which a bolt passing through the first connecting surface and used for fastening to the connecting object passes.

8. A connector, characterized in that, It has the busbar described in any one of claims 4 to 7.

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