Connection structure, busbars, and terminal blocks

Abstract

This invention provides a connection structure that improves heat resistance while connecting to an object by fitting an aluminum busbar to the object to be connected. [Solution] The first busbar (bus bar) 11 has a first base material 12 made of aluminum and a plate-shaped copper piece 13 joined to the first base material. A first contact portion S1 is formed on a part of the surface of the copper piece 13, and a joint portion B is arranged on the back surface of the copper piece 13, which corresponds to the area on the back surface of the copper piece 13 other than the part of the surface of the copper piece 13. The back surface of the copper piece is joined to the first base material at the joint portion B, and the first busbar and the second busbar are electrically connected to each other by the first contact portion contacting the second contact portion S2 of the second busbar (object to be connected) 21.

Description

Technical Field

[0001] The present invention relates to a connection structure, and particularly to a connection structure in which a bus bar made of aluminum as a base material is connected to a connection object by being fitted to the connection object. The present invention also relates to a bus bar used in such a connection structure and a terminal block having the bus bar.

Background Art

[0002] For example, the electrical connection between a motor device and an inverter device used in an electric vehicle is performed by connecting the motor-side bus bar and the inverter-side bus bar to each other. As such a bus bar, in order to suppress the amount of heat generated when an electric current flows between the motor device and the inverter device, a bus bar made of copper having a low contact resistance is often used. However, since a bus bar made of copper is heavy and relatively expensive, it is desired to use aluminum which is lightweight, has excellent electrical conductivity, and is relatively inexpensive.

[0003] In addition, the motor-side bus bar and the inverter-side bus bar are often bolted to each other, but there is also an increasing need for a structure that can easily connect the motor device and the inverter device by providing connectors to the motor device and the inverter device respectively and fitting the two connectors to each other.

[0004] Generally, in a connector in which a contact member contacts an elastic contact piece of a mating connector as the connector is mated, in order to improve heat resistance (resistance stability), the surfaces of the contact member and the elastic contact piece are plated.

[0005] For example, Patent Document 1 discloses a connector assembly in which, as shown in Figure 17, when a male connector 1 and a female connector 2 are mated, the round pin-shaped terminal body 4 of the male terminal fitting 3 of the male connector 1 contacts the elastic contact piece 6 of the female terminal fitting 5 of the female connector 2, and the outer surface of the terminal body 4 and the inner surface of the elastic contact piece 6 are plated with a silver alloy or the like. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-81734 [Overview of the project] [Problems that the invention aims to solve]

[0007] Similarly, when connecting the motor-side busbar and the inverter-side busbar by mating connectors, it is desirable to form a thin metal film, such as a plating layer, on the surface of each busbar. However, these busbars can be very long, depending on the arrangement of the motor and inverter units in an electric vehicle, for example, and it can be difficult to plate such busbars.

[0008] This invention was made to solve the problems of the conventional methods, and aims to provide a connection structure that can improve heat resistance while connecting to an object by fitting a busbar made of aluminum into the object to be connected. Furthermore, this invention also aims to provide a busbar used in such a connection structure, and a terminal block having a busbar. [Means for solving the problem]

[0009] Since it is difficult to directly apply plating treatment to busbars, the inventors considered forming a plating layer on the surface of a plate-shaped metal piece, and then joining the back side of this metal piece to the busbar, thereby using the surface of the metal piece with the plating layer as the contact point of the busbar.

[0010] In joining metal pieces, when the base material of the busbar is made of aluminum, we came up with the idea of ​​joining the metal piece to the busbar by ultrasonic welding, for example, in order to reduce the contact resistance between the busbar and the metal piece. By using ultrasonic welding, the metal atoms constituting the metal piece and the aluminum atoms constituting the base material of the busbar are metallically bonded, and the contact resistance between the busbar and the metal piece can be reduced without being affected by the oxide film formed on the surface of the busbar.

[0011] Therefore, an experiment was conducted to ultrasonically weld a copper piece to an aluminum busbar using an ultrasonic welding horn having a welding surface with multiple square pyramidal protrusions P formed thereon, as shown in Figure 1. As a result, the copper piece was joined to the busbar, but the shapes of the multiple protrusions P of the ultrasonic welding horn were transferred to the copper piece, and as shown in Figure 2, an uneven surface D was formed on the surface of the copper piece. Figure 3 shows a photograph of the surface of a copper piece after ultrasonic welding.

[0012] As described above, since uneven surfaces D are formed on the surface of the copper piece, even if a plating layer such as silver plating is formed on the surface of the copper piece beforehand, there is a concern that the plating layer will be destroyed by the protrusions P of the ultrasonic welding horn, and uneven surfaces D will be formed on the copper piece as well, exposing the copper in these uneven surfaces D. If copper is exposed from the plating layer, the heat resistance (resistive stability) will be significantly reduced, making it difficult to use the surface of the copper piece with the plated layer as a contact point.

[0013] The inventors conducted the above experiments and, after further intensive research, conceived the idea of ​​forming a contact point on a portion of the surface of a plate-shaped metal piece, and placing a joint on the back surface of the metal piece, corresponding to the area on the back of the metal piece that is not part of the surface, thereby joining the metal piece to the base material of the busbar. In other words, they considered joining the metal piece and the base material of the busbar using a joint located on the back surface of the metal piece that is not part of the contact point, thereby not involving the contact point in the joining process. By realizing this idea, they completed the first invention described below.

[0014] Furthermore, the inventors considered joining a plate-shaped metal piece to the base material of a busbar, and then fastening a metal contact-forming plate to the base material and the metal piece using fastening members so that it contacts the metal piece, thereby forming a contact portion on the surface of the protruding portion of the contact-forming plate that extends from the base material and the metal piece. By realizing this idea, the inventors completed the second invention described below.

[0015] The connection structure according to the first invention is, A connection structure in which a busbar is fitted to an object to be connected, The busbar includes a first base material made of aluminum and a plate-shaped metal piece joined to the first base material. A first contact point is formed on a portion of the surface of the metal piece. The joint is positioned in the area on the back of the metal piece that corresponds to the area on the surface of the metal piece other than a certain area. The back surface of the metal piece is joined to the first base material at the joint. The busbar and the object to be connected are electrically connected when the first contact point of the busbar comes into contact with the second contact point of the object to be connected.

[0016] The region where the first contact point is formed is the central part of the surface of the metal piece, and the joint can be positioned to surround the first contact point. Alternatively, the region where the first contact point is formed may be the central part of the surface of the metal piece, and the joints may be arranged on both sides of the first contact point so as to sandwich it. The metal piece preferably consists of a copper piece joined to the first base material by any one of ultrasonic welding, laser welding, and resistance welding. Also, the bus bar includes a silver plating layer formed on the surface of the metal piece, and the first contact portion is preferably formed on the silver plating layer.

[0017] The bus bar according to the first invention is a bus bar that is connected to a connection target by being fitted to the connection target, a first base material made of aluminum, a plate-shaped metal piece joined to the first base material, and is provided with a first contact portion is formed on a partial region of the surface of the metal piece, a joint portion is arranged in a region of the back surface of the metal piece corresponding to a region other than the partial region on the surface of the metal piece, the back surface of the metal piece is joined to the first base material at the joint portion, and the first contact portion is electrically connected to the connection target by contacting the second contact portion of the connection target.

[0018] The partial region where the first contact portion is formed is the central portion of the surface of the metal piece, and the joint portion can be arranged so as to surround the periphery of the first contact portion. Alternatively, the partial region where the first contact portion is formed is the central portion of the surface of the metal piece, and the joint portion may be arranged on both sides of the first contact portion so as to sandwich the first contact portion. The metal piece preferably consists of a copper piece joined to the first base material by any one of ultrasonic welding, laser welding, and resistance welding. Also, it includes a silver plating layer formed on the surface of the metal piece, and the first contact portion is preferably formed on the silver plating layer.

[0019] The terminal block according to the first invention has the bus bar of the first invention described above.

[0020] The connection structure according to the second invention is A connection structure in which a busbar is fitted to an object to be connected, The bus bar is A first base material made of aluminum, A plate-shaped metal piece to be joined to the first base material, A metal contact-forming plate that contacts the metal piece and extends from the first base material and the metal piece, A fastening member that fastens the contact-forming plate to the first base material and the metal piece. Includes, A first contact portion is formed on the surface of the protruding portion of the contact-forming plate that extends from the first base material and the metal piece. The busbar and the object to be connected are electrically connected when the first contact point of the busbar comes into contact with the second contact point of the object to be connected.

[0021] The fastening member is preferably a bolt, screw, or rivet. The metal piece is preferably made of a copper piece joined to the first base material by ultrasonic welding, laser welding, or resistance welding. Furthermore, the contact-forming plate is preferably made of a copper plate with a silver-plated layer formed on its surface, and the first contact portion is preferably formed in the silver-plated layer.

[0022] The busbar relating to the second invention is, A busbar that is connected to an object by fitting into the object to be connected, A first base material made of aluminum, A plate-shaped metal piece to be joined to the first base material, A metal contact-forming plate that contacts the metal piece and extends from the first base material and the metal piece, A fastening member that fastens the contact-forming plate to the first base material and the metal piece. Equipped with, A first contact portion is formed on the surface of the protruding portion of the contact-forming plate that extends from the first base material and the metal piece. The device is electrically connected to an object by the first contact point contacting the second contact point of the object to be connected.

[0023] The fastening member is preferably a bolt, screw, or rivet. The metal piece is preferably made of a copper piece joined to the first base material by ultrasonic welding, laser welding, or resistance welding. Furthermore, the contact-forming plate is preferably made of a copper plate with a silver-plated layer formed on its surface, and the first contact portion is preferably formed in the silver-plated layer.

[0024] The terminal block according to the second invention has the busbar of the second invention described above. [Effects of the Invention]

[0025] According to the first invention, the busbar includes a first base material made of aluminum and a plate-shaped metal piece joined to the first base material, a first contact portion is formed in a part of the surface of the metal piece, a joint portion is arranged in the area on the back of the metal piece that corresponds to the area on the surface of the metal piece other than the part of the surface of the metal piece, the back of the metal piece is joined to the first base material at the joint portion, and the busbar and the object to be connected are electrically connected to each other by the first contact portion contacting the second contact portion of the object to be connected, so that by fitting the busbar made of aluminum into the object to be connected, it is possible to improve the heat resistance while connecting to the object to be connected. Furthermore, the second invention also makes it possible to improve heat resistance while connecting to an object by fitting an aluminum busbar to the object to be connected. [Brief explanation of the drawing]

[0026] [Figure 1] This is a perspective view showing the protrusions formed on the welding surface of an ultrasonic welding horn. [Figure 2] This is a partial perspective view showing the surface of a copper piece that has been ultrasonically welded. [Figure 3] This is a photograph showing a portion of the surface of a copper piece that has been ultrasonically welded. [Figure 4] This is a perspective view showing a connection structure according to Embodiment 1 of the present invention. [Figure 5]This is a cross-sectional view showing the connection structure according to Embodiment 1. [Figure 6] This is a perspective view showing how the first base material is positioned on the ultrasonic welding anvil and fixing jig when manufacturing the first busbar in Embodiment 1. [Figure 7] This is a perspective view showing how copper pieces are arranged on the surface of the first base material when manufacturing the first busbar in Embodiment 1. [Figure 8] This is a perspective view showing how the ultrasonically welded horn is placed on the silver-plated layer of the copper piece when manufacturing the first busbar in Embodiment 1. [Figure 9] This is a perspective view showing the welding surface of the ultrasonic welding horn used in Embodiment 1. [Figure 10] This is a perspective view showing the state in which a copper piece is ultrasonically welded onto the surface of the first base material when manufacturing the first busbar in Embodiment 1. [Figure 11] This is a perspective view showing the surface of the copper piece and silver plating layer that were ultrasonically welded in Embodiment 1. [Figure 12] This is a perspective view showing the state of the connection structure according to Embodiment 1 before connection. [Figure 13] This is a perspective view showing a terminal block having six first busbars in Embodiment 1, with six second busbars, which are to be connected, aligned. [Figure 14] This is a perspective view showing the state in which the second busbars, which are to be connected, are connected to each of the six first busbars in Embodiment 1 of the terminal block. [Figure 15] This is a perspective view showing the surface of the copper piece and silver plating layer that were ultrasonically welded in Embodiment 2. [Figure 16] This is a cross-sectional view showing the connection structure according to Embodiment 3. [Figure 17] This is a cross-sectional view showing a conventional connector assembly. [Modes for carrying out the invention]

[0027] Embodiments of this invention will be described below with reference to the attached drawings. Embodiment 1 Figures 4 and 5 show a connection structure according to Embodiment 1 of the present invention. The connection structure comprises a first busbar 11 and a second busbar 21. The first busbar 11 has a flat plate-shaped first base material 12 made of aluminum that extends in a predetermined direction, and the second busbar 21 has a flat plate-shaped second base material 22 made of aluminum that extends in the same predetermined direction as the first busbar 11. The first busbar 11 constitutes the "busbar" of the present invention, and the second busbar 21 constitutes the "object to be connected" of the present invention.

[0028] For convenience, the direction in which the first base material 12 and the second base material 22 extend will be called the Y direction, the width direction of the first base material 12 and the second base material 22 will be called the X direction, and the direction perpendicular to both the Y direction and the X direction will be called the Z direction.

[0029] The first busbar 11 has a plate-shaped copper piece 13 joined to the surface on the +Z direction side at the +Y direction end of the first base material 12, and a silver-plated layer 14 formed on the surface on the +Z direction side of the copper piece 13. A rectangular first contact portion S1 facing the +Z direction is formed in the central part of the silver-plated layer 14.

[0030] Furthermore, on the back surface of the copper piece 13 on the -Z direction side, a joint B is positioned in a frame-shaped region corresponding to the periphery of the first contact portion S1, surrounding the first contact portion S1. At this joint B, the back surface of the copper piece 13 on the -Z direction side is joined to the first base material 12 by metallic bonding. That is, at the interface between the first base material 12 and the copper piece 13 at joint B, the copper atoms constituting the copper piece 13 are metallically bonded to the aluminum atoms constituting the first base material 12, and no oxide film exists between the first base material 12 and the copper piece 13.

[0031] On the other hand, the second busbar 21 has a conductive connector 23 attached to the -Y end of the second base material 22. The connector 23 is for fitting the +Y end of the first busbar 11 and has a pair of elastic contact pieces 23A that protrude toward the first busbar 11 in the -Y direction and are elastically deformable in the Z direction. The pair of elastic contact pieces 23A face each other in the Z direction, and a second contact portion S2 facing the -Z direction is formed at the -Y end of the elastic contact piece 23A that is positioned on the +Z side of the pair of elastic contact pieces 23A. Furthermore, the +Y direction ends of the pair of elastic contact pieces 23A are electrically connected to the second base material 22.

[0032] Next, a method for fabricating the first busbar 11 with this configuration will be described. As shown in Figure 6, a fixing jig 32 is positioned on the ultrasonic welding anvil 31. The fixing jig 32 has a notch 32A for accommodating a flat first base material 12, and the first base material 12 is fixed to the surface of the ultrasonic welding anvil 31 on the +Z direction side by being accommodated in the notch 32A of the fixing jig 32.

[0033] Next, as shown in Figure 7, the copper piece 13 is placed on the surface of the first base material 12 on the +Z direction side. Furthermore, a silver plating layer 14 is pre-formed on the surface of the copper piece 13 in the +Z direction, and the back surface of the copper piece 13 in the -Z direction is in contact with the surface of the first base material 12 in the +Z direction. Since the copper piece 13 is smaller in size than the first base material 12, plating can be easily applied to the surface of the copper piece 13.

[0034] Furthermore, as shown in Figure 8, an ultrasonic welding horn 33 is positioned on the silver-plated layer 14 of the copper piece 13. As shown in Figure 9, a planar, frame-shaped welding surface 33A is formed at the -Z side end of the ultrasonic welding horn 33, extending along the XY plane. The welding surface 33A has an outer shape corresponding to the copper piece 13, and a rectangular recess 33B is formed in the central part of the welding surface 33A, recessed toward the +Z direction. Multiple square pyramidal protrusions 33C are formed on this frame-shaped welding surface 33A, arranged in the X and Y directions and projecting toward the -Z direction.

[0035] For example, the multiple protrusions 33C are arranged at a pitch of approximately 0.3 to 2.5 mm in the X and Y directions, respectively. Each protrusion 33C has a shape in which the four triangular sides constituting a square pyramid rise at a 45-degree angle to the welding surface 33A, and has a height of 0.15 to 0.8 mm in the -Z direction from the welding surface 33A. However, these arrangement pitches, rising angles, and heights are merely examples and can be appropriately changed depending on the size of the copper piece 13, etc.

[0036] The rectangular recess 33B formed in the central part of the welding surface 33A corresponds to the first contact portion S1 formed in the silver plating layer 14, and the frame-shaped welding surface 33A corresponds to the joint portion B located on the back surface of the copper piece 13 in the -Z direction.

[0037] With the welding surface 33A in contact with the silver plating layer 14, ultrasonic vibrations are applied to the ultrasonic welding horn 33 while applying pressure to the ultrasonic welding horn 33 in the -Z direction. The ultrasonic vibrations applied to the ultrasonic welding horn 33 are transmitted from the welding surface 33A of the ultrasonic welding horn 33 to the silver plating layer 14 and the copper piece 13, propagate within the copper piece 13, and generate friction between the joint B located on the -Z side back surface of the copper piece 13 and the +Z side surface of the first base material 12. As a result, the oxide film formed on the surface of the first base material 12 and the back surface of the copper piece 13 that are in contact with each other at the joint B is destroyed, and the aluminum atoms constituting the first base material 12 and the copper atoms constituting the copper piece 13 mix together and form a metallic bond.

[0038] Simultaneously, the ultrasonic vibrations applied to the ultrasonic welding horn 33 cause friction between the welding surface 33A of the ultrasonic welding horn 33 and the surface of the copper piece 13 on which the silver-plated layer 14 is formed, on the +Z side. As shown in Figure 10, in the region corresponding to the frame-shaped welding surface 33A, the multiple protrusions 33C of the welding surface 33A create uneven surfaces 15 on the silver-plated layer 14 and the copper piece 13. These uneven surfaces 15 are formed as traces of the ultrasonic welding of the copper piece 13 to the first base material 12. The multiple square pyramidal protrusions 33C of the welding surface 33A bite into the silver-plated layer 14 and the copper piece 13, transferring the shapes of the multiple protrusions 33C to the silver-plated layer 14 and the copper piece 13.

[0039] As a result, as shown in Figure 11, an uneven surface 15 is formed on the surface of the silver plating layer 14 and the copper piece 13. Therefore, there is a concern that a portion of the silver plating layer 14 will be destroyed in the uneven surface 15, exposing the copper of the copper piece 13.

[0040] However, the uneven shape portion 15 is formed only in the region corresponding to the welding surface 33A of the frame shape of the ultrasonic welding horn 33, where multiple protrusions 33C are present. In other words, the uneven shape portion 15 is not formed in the first contact portion S1 formed in the central part of the silver plating layer 14, and copper is not exposed in the first contact portion S1. Therefore, the first contact portion S1 maintains its heat resistance (resistive stability) due to the presence of the silver plating layer 14.

[0041] Furthermore, since the back surface on the -Z direction side of the joint B of the copper piece 13 and the surface on the +Z direction side of the first base material 12 are metallically bonded to each other, the first base material 12, despite being made of aluminum, is connected to the copper piece 13 via the joint B with low contact resistance, and is further electrically connected to the first contact portion S1 formed in the central part of the silver plating layer 14. In this way, the fabrication of the first busbar 11 is completed.

[0042] When connecting the second busbar 21 to the first busbar 11, as shown in Figure 12, the second busbar 21 is positioned on the +Y side of the first busbar 11, then the first busbar 11 and the second busbar 21 are moved so that they are relatively close to each other, and the +Y end of the first busbar 11 is inserted between the pair of elastic contact pieces 23A of the connection portion 23 of the second busbar 21, thereby fitting the first busbar 11 into the connection portion 23 of the second busbar 21.

[0043] As a result, as shown in Figures 4 and 5, the first base material 12, copper piece 13, and silver plating layer 14 at the +Y direction end of the first busbar 11 are sandwiched between a pair of elastic contact pieces 23A of the connecting portion 23 of the second busbar 21, and the second contact portion S2 formed on the elastic contact piece 23A positioned on the +Z direction side elastically contacts the first contact portion S1 formed in the central part of the silver plating layer 14. In this way, 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 connection portion 23.

[0044] In the above embodiment 1, a plate-shaped copper piece 13 is joined to the surface of the first base material 12 of the first busbar 11 by ultrasonic welding. However, the invention is not limited to this, and other joining methods may be used as long as the copper piece 13 can be joined to the first base material 12 with low contact resistance by destroying the oxide film formed on the surface of the first base material 12 made of aluminum. For example, the copper piece 13 can also be joined to the first base material 12 using laser welding, resistance welding, etc.

[0045] Furthermore, the metal piece joined to the first base material 12 is not limited to the copper piece 13; plate-shaped metal pieces made of other metals can also be used as long as they can be joined to the first base material 12 with low contact resistance. Furthermore, although a silver plating layer 14 is formed on the surface of the copper piece 13, a plating layer of another metal may be formed instead of the silver plating layer 14. Instead of plating the surface of the copper piece 13, for example, a thin silver film can be attached to the surface of the copper piece 13. Alternatively, a portion of the surface of the copper piece 13 can be used as the first contact portion S1 without forming a plating layer or the like on the surface of the copper piece 13.

[0046] Figure 13 shows a terminal block having first busbars 11. The terminal block has, for example, six first busbars 11 held in a housing 41 made of an insulating material. Six second busbars 21 are arranged on the +Y direction side of the six first busbars 11. By moving the six second busbars 21 relative to the six first busbars 11 of the terminal block in the -Y direction, as shown in Figure 14, the +Y end of each first busbar 11 is fitted into the corresponding connection portion 23 of the second busbar 21, and the second contact portion S2 of the second busbar 21 elastically contacts the first contact portion S1 of the first busbar 11. In this way, the six first busbars 11 and the six second busbars 21 can be electrically connected by mating action alone. Note that the number of busbars in the first bus bar 11 is not limited to six.

[0047] Embodiment 2 In the above embodiment 1, the back surface of the copper piece 13 on the -Z direction side is joined to the first base material 12 at a joint B that is arranged in a frame-shaped region corresponding to the periphery of the first contact portion S1 so as to surround the first contact portion S1. As a result, as shown in Figure 11, an uneven shape portion 15 is formed on the surface of the silver plating layer 14 and the copper piece 13 over the frame-shaped region.

[0048] However, this is not the only limitation; the back surface of the copper piece 13 on the -Z side is joined to the first base material 12 at a joint located in the area corresponding to the periphery of the first contact portion S1. For example, joints can be arranged on both sides of the first contact portion S1 on the back surface of the copper piece 13 on the -Z side, so as to sandwich the first contact portion S1. In this case, as shown in Figure 15, uneven surfaces 15 are formed on the silver plating layer 14 and the copper piece 13 on both sides of the first contact portion S1 in the Y direction, or on both sides in the X direction. In this manner, the first busbar 11 and the second busbar 21 can be electrically connected, similar to the first embodiment.

[0049] Furthermore, in embodiments 1 and 2 described above, the first contact portion S1 is formed in the central part of the silver plating layer 14, but the invention is not limited to this. The first contact portion S1 may be formed in a part of the silver plating layer 14, and the joint portion B may be located in the area on the back surface of the copper piece 13 that corresponds to the area of ​​the silver plating layer 14 other than the part of the silver plating layer 14. For example, the first contact portion S1 may be formed in the peripheral part of the silver plating layer 14 excluding the central part, and the joint portion B may be located in the central part of the back surface of the copper piece 13.

[0050] Embodiment 3 Figure 16 shows the connection structure according to Embodiment 3. This connection structure is the same as the connection structure of Embodiment 1 shown in Figures 4 and 5, but uses a first bus bar 51 instead of the first bus bar 11.

[0051] The first busbar 51 has a flat plate-shaped first base material 52 made of aluminum that extends in the Y direction. A stepped portion 52A is formed at the +Y direction end of the first base material 52, where the -Z direction portion of the first base material 52 is cut out, and a plate-shaped metal piece 53 is joined to the surface of the stepped portion 52A facing the -Z direction. A metal contact-forming plate 54 extending in the Y direction is in contact with the metal piece 53, and the contact-forming plate 54 is fastened to the first base material 52 and the metal piece 53 by bolts 61 and nuts 62. The first busbar 51 is composed of the first base material 52, the metal piece 53, the contact-forming plate 54, the bolts 61 and nuts 62. A copper piece is used as the metal piece 53, and a copper plate with a silver plating layer 55 formed on its surface is used as the contact forming plate 54. The bolt 61 and nut 62 constitute fastening members for fastening the contact-forming plate 54 to the first base material 52 and the metal piece 53.

[0052] Similar to Embodiment 1, the metal piece 53 can be ultrasonically welded to the first base material 52 using an ultrasonic welding anvil and an ultrasonic welding horn. Specifically, the first base material 52 is placed on the surface of the ultrasonic welding anvil so that the surface of the first base material 52 in the +Z direction faces the ultrasonic welding anvil, the metal piece 53 is placed on the -Z direction surface of the stepped portion 52A of the first base material 52, and the ultrasonic welding horn is placed on top of the metal piece 53. The ultrasonic welding horn has a plurality of square pyramidal protrusions across the entire surface of the welding surface facing the metal piece 53. In this state, the metal piece 53 is ultrasonically welded to the first base material 52 by applying ultrasonic vibration to the ultrasonic welding horn.

[0053] At this time, a surface on the -Z direction side of the metal piece 53 is formed with a surface featuring multiple square pyramidal depressions, which are traces of when the metal piece 53 was ultrasonically welded to the first base material 52. As the metal piece 53 is ultrasonically welded to the first base material 52, the +Z-direction surface of the metal piece 53 is joined to the stepped portion 52A of the first base material 52 by metallic bonding. That is, at the interface between the first base material 52 and the metal piece 53, the copper atoms constituting the metal piece 53 are metallically bonded to the aluminum atoms constituting the first base material 52, and no oxide film exists between the first base material 52 and the metal piece 53.

[0054] Therefore, even if the first base material 52 is made of aluminum, the contact resistance between the first base material 52 and the metal piece 53 made of copper can be reduced. The first base material 52, the metal piece 53, and the contact-forming plate 54 each have through holes 52H, 53H, and 54H, respectively. By passing bolts 61 through these through holes 52H, 53H, and 54H and tightening nuts 62, the contact-forming plate 54 is fastened to the first base material 52 and the metal piece 53 while being pressed against them.

[0055] The contact-forming plate 54 extends longer in the Y direction than the stepped portion 52A of the first base material 52, and has a protruding portion F that extends further in the +Y direction than the first base material 52 and the metal piece 53. A silver plating layer 55 is formed on the surface of the contact-forming plate 54, and the first contact portion S1 of the first bus bar 51 is formed on the silver plating layer 55 at the protruding portion F. Since the contact-forming plate 54 is fastened to the first base material 52 and the metal piece 53 using bolts 61 and nuts 62, the contact resistance between the metal piece 53, which is made of copper, and the contact-forming plate 54, which is made of copper, is low.

[0056] The first bus bar 51 is moved relative to the second bus bar 21, and the protruding portion F of the contact forming plate 54 located at the +Y end of the first bus bar 51 is inserted between the pair of elastic contact pieces 23A of the connection portion 23 of the second bus bar 21, thereby fitting the first bus bar 51 into the connection portion 23 of the second bus bar 21. As a result, the protruding portion F of the contact-forming plate 54, on which the silver-plated layer 55 is formed on its surface, is sandwiched between a pair of elastic contact pieces 23A of the connecting portion 23 of the second busbar 21, and the second contact portion S2 formed on the elastic contact piece 23A elastically contacts the first contact portion S1 formed on the silver-plated layer 55.

[0057] In this way, the first base material 52 of the first busbar 51 is electrically connected to the second base material 22 of the second busbar 21 via the connection portion 23. Furthermore, since a silver plating layer 55 is formed on the surface of the contact forming plate 54 of the first busbar 51, the first contact portion S1 maintains its heat resistance (resistive stability). Furthermore, in the first busbar 51, the contact forming plate 54 is fastened to the first base material 52 and the metal piece 53 using bolts 61 and nuts 62. By increasing the fastening torque, the contact resistance between the first base material 52 and the metal piece 53, and the contact resistance between the metal piece 53 and the contact forming plate 54 can be further reduced.

[0058] In the above embodiment 3, a plate-shaped metal piece 53 is joined to the first base material 52 of the first busbar 51 by ultrasonic welding. However, the invention is not limited to this, and other joining methods may be used as long as the metal piece 53 can be joined to the first base material 52 with low contact resistance by destroying the oxide film formed on the surface of the first base material 52, which is made of aluminum. For example, the metal piece 53 can also be joined to the first base material 52 using laser welding, resistance welding, etc.

[0059] Furthermore, the metal piece 53 joined to the first base material 52 is not limited to a copper piece; any plate-shaped metal piece made of other metals can be used as long as it can be joined to the first base material 52 with low contact resistance. Furthermore, the contact-forming plate 54, which is fastened to the first base material 52 and the metal piece 53 using bolts 61 and nuts 62, is not limited to a copper plate; other metal plate members can also be used as long as they can make contact with the metal piece 53 with low contact resistance.

[0060] Furthermore, the fastening of the contact-forming plate 54 to the first base material 52 and the metal piece 53 is not limited to the method using bolts 61 and nuts 62. For example, the contact-forming plate 54 can also be fastened to the first base material 52 and the metal piece 53 by screw fastening, riveting, etc.

[0061] Furthermore, although a silver plating layer 55 is formed on the surface of the contact-forming plate 54, a plating layer of another metal may be formed instead of the silver plating layer 55. Instead of applying a plating treatment to the surface of the contact-forming plate 54, for example, a thin silver film can be attached to the surface of the contact-forming plate 54. Also, it is not necessarily required to form a plating layer on the surface of the contact-forming plate 54, but it is desirable to form a plating layer on the surface of the contact-forming plate 54 in order to maintain the heat resistance (resistive stability) of the first contact portion S1.

[0062] A terminal block having a plurality of first busbars 51 according to Embodiment 3 can be configured, similar to the terminal blocks shown in Figures 13 and 14.

[0063] Furthermore, this invention is not limited to the connection of the first busbars 11 and 51 to the second busbar 21, but can also be applied to connection structures in which a connection target such as a terminal is used instead of the second busbar 21, and the first busbars 11 and 51 are electrically connected to the connection target by fitting them to the connection target. [Explanation of symbols]

[0064] 1 Male connector, 2 Female connector, 3 Male terminal fitting, 4 Terminal body, 5 Female terminal fitting, 6 Elastic contact piece, 11, 51 First bus bar, 12, 52 First base material, 13 Copper piece, 14 Silver plating layer, 15 Uneven shape part, 21 Second bus bar, 22 Second base material, 23 Connection part, 23A Elastic contact piece, 31 Ultrasonic welding anvil, 32 Fixing jig, 32A Notch, 33 Ultrasonic welding horn, 33A Welding surface, 33B Recess, 33C Protrusion, 41 Housing, 53 Metal piece, 54 Contact forming plate, 55 Silver plating layer, 61 Bolt, 62 Nut, 52H, 53H, 54H Through hole, P Protrusion, D Uneven shape part, F Overhang, S1 First contact part, S2 Second contact part, B Joint part.

Claims

1. A connection structure in which a busbar is fitted to an object to be connected, thereby connecting to the object to be connected, The busbar includes a first base material made of aluminum and a plate-shaped metal piece joined to the first base material. A first contact portion is formed on a part of the surface of the metal piece. The joint is positioned in the area on the back surface of the metal piece that corresponds to an area on the surface of the metal piece other than the area on the surface of the metal piece. The back surface of the metal piece is joined to the first base material at the joint, A connection structure in which the busbar and the object to be connected are electrically connected to each other by the first contact portion contacting the second contact portion of the object to be connected.

2. The region in which the first contact portion is formed is the central portion of the surface of the metal piece. The connection structure according to claim 1, wherein the joint portion is arranged to surround the first contact portion.

3. The region in which the first contact portion is formed is the central portion of the surface of the metal piece. The connection structure according to claim 1, wherein the connecting portion is arranged on both sides of the first contact portion so as to sandwich the first contact portion.

4. The connection structure according to claim 1, wherein the metal piece is a copper piece joined to the first base material by ultrasonic welding, laser welding, or resistance welding.

5. The bus bar includes a silver plating layer formed on the surface of the metal piece. The connection structure according to claim 1, wherein the first contact portion is formed in the silver plating layer.

6. A busbar that is connected to an object by fitting into the object to be connected, A first base material made of aluminum, A plate-shaped metal piece joined to the first base material and Equipped with, A first contact portion is formed on a part of the surface of the metal piece. The joint is positioned in the area on the back surface of the metal piece that corresponds to an area on the surface of the metal piece other than the aforementioned partial area. The back surface of the metal piece is joined to the first base material at the joint, A busbar that is electrically connected to an object by the first contact portion contacting the second contact portion of the object to be connected.

7. The region in which the first contact portion is formed is the central portion of the surface of the metal piece. The bus bar according to claim 6, wherein the joint portion is arranged to surround the first contact portion.

8. The region in which the first contact portion is formed is the central portion of the surface of the metal piece. The bus bar according to claim 6, wherein the connecting portion is arranged on both sides of the first contact portion so as to sandwich the first contact portion.

9. The busbar according to claim 6, wherein the metal piece is a copper piece joined to the first base material by ultrasonic welding, laser welding, or resistance welding.

10. The silver plating layer formed on the surface of the metal piece is included, The bus bar according to claim 6, wherein the first contact portion is formed in the silver plating layer.

11. A terminal block having the busbar according to any one of claims 6 to 10.

12. A connection structure in which a busbar is fitted to an object to be connected, thereby connecting to the object to be connected, The aforementioned busbar is A first base material made of aluminum, A plate-shaped metal piece joined to the first base material, A metal contact-forming plate that contacts the metal piece and extends from the first base material and the metal piece, A fastening member for fastening the contact forming plate to the first base material and the metal piece. Includes, A first contact portion is formed on the surface of the protruding portion of the contact-forming plate that extends from the first base material and the metal piece. A connection structure in which the busbar and the object to be connected are electrically connected to each other by the first contact portion contacting the second contact portion of the object to be connected.

13. The connection structure according to claim 12, wherein the fastening member is one of a bolt, a screw, and a rivet.

14. The connection structure according to claim 12, wherein the metal piece is a copper piece joined to the first base material by ultrasonic welding, laser welding, or resistance welding.

15. The contact-forming plate is made of a copper plate with a silver-plated layer formed on its surface. The connection structure according to claim 12, wherein the first contact portion is formed in the silver plating layer.

16. A busbar that is connected to an object by fitting into the object to be connected, A first base material made of aluminum, A plate-shaped metal piece joined to the first base material, A metal contact-forming plate that contacts the metal piece and extends from the first base material and the metal piece, A fastening member for fastening the contact forming plate to the first base material and the metal piece. Equipped with, A first contact portion is formed on the surface of the protruding portion of the contact-forming plate that extends from the first base material and the metal piece. A busbar that is electrically connected to an object by the first contact portion contacting the second contact portion of the object to be connected.

17. The bus bar according to claim 16, wherein the fastening member is any one of a bolt, a screw, or a rivet.

18. The busbar according to claim 16, wherein the metal piece is a copper piece joined to the first base material by ultrasonic welding, laser welding, or resistance welding.

19. The contact-forming plate is made of a copper plate with a silver-plated layer formed on its surface. The bus bar according to claim 16, wherein the first contact portion is formed in the silver plating layer.

20. A terminal block having the busbar according to any one of claims 16 to 19.

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