Secondary battery and battery pack in which secondary batteries are combined

Abstract

The present invention provides a secondary battery and a battery pack that make it possible to highly accurately position a voltage detection terminal with respect to a bus bar and reliably maintain a positioning position.　The present invention is characterized by comprising a bus bar 302, a voltage detection terminal 401 which is welded to the bus bar, and a bus bar holder 311 in which a placement region for the bus bar and the voltage detection terminal is provided, wherein: the voltage detection terminal has a voltage detection terminal-side positioning part 421a; the bus bar holder has a bus bar holder-side positioning part 331a that engages with the voltage detection terminal-side positioning part to determine the position of the voltage detection terminal; and a positioning position maintaining part 341 that contacts a non-welded surface of the voltage detection terminal on the opposite side from a welded surface at which the voltage detection terminal is welded to the bus bar is formed in the bus bar holder-side positioning part.

Description

Secondary batteries and battery packs combining secondary batteries

[0001] The present invention relates to a secondary battery and a battery pack incorporating such secondary batteries.

[0002] 2. Description of the Related Art Lithium ion secondary batteries with high energy density have been developed as power sources for vehicles such as electric vehicles.

[0003] This secondary battery is made by winding a positive electrode, which has a positive electrode foil coated on both sides with a positive electrode active material, and a negative electrode, which has a negative electrode foil coated on both sides with a negative electrode active material, with a separator interposed between them, in a flat shape, and housing this wound body (electrode body) and electrolyte solution in a rectangular battery container. Note that secondary batteries using solid electrolytes have also been developed, and the present invention also covers secondary batteries using these solid electrolytes.

[0004] There is known a battery pack in which the terminals of a plurality of secondary batteries are electrically connected by bus bars and which has voltage detection terminals for measuring the voltage of each secondary battery. For example, Patent Document 1 listed below discloses a holding structure in which the voltage detection terminals for measuring the voltage of the secondary batteries are held in a bus bar holding section that houses the bus bars that electrically connect the secondary batteries to each other.

[0005] The voltage detection terminal of Patent Document 1 includes an electrical connection portion connected to the bus bar, an electric wire connection portion to which an electric wire is connected, and a temporary fixing portion provided between the electrical connection portion and the electric wire connection portion, which restricts movement along the axis of the end of the electric wire connected to the electric wire connection portion and is temporarily fixed to the bus bar holding portion in a state where displacement in a direction perpendicular to the axis and rotation about the axis are allowed.

[0006] Patent Document 1 states that such a configuration makes it possible to reliably position the voltage detection terminals relative to the bus bar holding portion while reducing unnecessary portions.

[0007] JP 2018-81875 A

[0008] However, it is not easy to position the voltage detection terminals with respect to the bus bars with high precision and to reliably maintain the positions, which has been a factor in increasing the manufacturing costs of the battery pack.

[0009] An object of the present invention is to provide a secondary battery and a battery pack in which voltage detection terminals can be positioned with high precision relative to bus bars and the positioned positions can be reliably maintained.

[0010] The present invention is characterized in that it comprises a busbar, a voltage detection terminal welded to the busbar, and a busbar holder provided with a mounting area for the busbar and the voltage detection terminal, wherein the voltage detection terminal has a voltage detection terminal side positioning portion, and the busbar holder has a busbar holder side positioning portion that engages with the voltage detection terminal side positioning portion to determine the position of the voltage detection terminal, and a positioning position maintaining portion that contacts the non-welded surface opposite to the welded surface of the voltage detection terminal that is welded to the busbar is formed on the busbar holder side positioning portion.

[0011] According to the present invention, it is possible to provide a secondary battery and a battery pack in which the voltage detection terminals can be positioned with high precision relative to the bus bars and the positioned positions can be reliably maintained.

[0012] 12 is a perspective view showing a battery pack according to an embodiment; FIG. 13 is a perspective view showing components of a secondary battery and a holding unit exploded in the stacking direction X; FIG. 14 is a perspective view showing the configuration of a busbar unit and a voltage detection unit according to a first embodiment; FIG. 15 is a top view showing the busbar unit and the voltage detection unit when viewed from the direction R in FIG. 3; FIG. 16 is a bottom view showing the busbar unit and the voltage detection unit when viewed from the direction F in FIG. 3; and FIG. 17 is an enlarged view of a portion indicated by P in FIG. 4. FIG. 18 is a perspective view showing the arrangement of busbars and voltage detection terminals; FIG. 19 is a top view showing a positioning portion of a busbar; FIG. 20 is a top view showing a positioning portion of a voltage detection terminal; FIG. 21 is a top view showing a state in which busbars and voltage detection terminals are housed in a busbar holder; and FIG. 22 is a bottom view showing a state in which busbars and voltage detection terminals are housed in a busbar holder. A configuration diagram showing the arrangement of busbars and voltage detection terminals according to a first embodiment of the present invention. A configuration diagram showing a state before the voltage detection terminals are assembled to the busbar holder according to a first embodiment of the present invention. A cross-sectional view showing the A-A cross section of FIG. 12. A perspective view showing the arrangement of busbars and voltage detection terminals. 16 is a configuration diagram showing a state before a voltage detection terminal according to a second embodiment of the present invention is assembled to a bus bar holder. FIG. 17 is a cross-sectional view showing the B-B cross section of FIG. 16. FIG. 18 is a perspective view showing an arrangement of bus bars and voltage detection terminals according to a third embodiment of the present invention. FIG. 19 is a perspective view of the voltage detection terminal shown in FIG.

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and various modifications and applications within the technical concept of the present invention are also included within its scope. <Configuration of Battery Assembly 1> The configuration of the battery assembly 1 according to the embodiment will be described with reference to FIGS. 1 and 2. Embodiments for carrying out the present invention will be described with reference to the drawings. To facilitate understanding of each embodiment, the size and proportions of components may be exaggerated in each drawing. The same reference numerals are assigned to the same components in each drawing. In each drawing, the stacking direction X, width direction Y, and height direction Z of the battery assembly 1 are indicated by arrows.

[0014] However, in each drawing, the stacking direction X, width direction Y, and height direction Z of the battery pack 1 indicate the relative positional relationship within the same drawing. That is, if the battery pack 1 is rotated 180 degrees and placed with the top and bottom faces reversed, or if the battery pack 1 is rotated 90 degrees and placed with the top face as the side, the stacking direction X, width direction Y, and height direction Z of the battery pack 1 will change. In each drawing, the threads on the outer surfaces of the fastening bolts and the grooves on the inner surfaces of the insert nuts are not shown.

[0015] Fig. 1 is a perspective view showing a battery pack 1 according to an embodiment. Fig. 2 is a perspective view showing components of a secondary battery 100 and a holding unit 200 in a state where they are disassembled in a stacking direction X.

[0016] The battery pack 1 is configured as, for example, a power source for operating a motor for running a vehicle. The battery pack 1 may also be configured as, for example, a power source for operating electrical equipment mounted on the vehicle.

[0017] As shown in FIG. 1 , the battery pack 1 includes a plurality of secondary batteries 100, a holding unit 200 that holds the plurality of secondary batteries 100, and a bus bar unit 300 that electrically connects the plurality of secondary batteries 100. The battery pack 1 also includes a voltage detection unit 400 that detects the voltage of the secondary batteries 100, and a temperature measurement unit (not shown) that measures the temperature of the secondary batteries 100. (Configuration of Secondary Battery 100) As shown in FIG. 1 , the secondary batteries 100 are stacked in a stacking direction X via the holding unit 200. For example, 24 secondary batteries 100 are stacked. The secondary batteries 100 are, for example, lithium-ion secondary batteries. The secondary batteries 100 include current collectors and an electrolyte.

[0018] 2, the secondary battery 100 includes a container 101, a lid 102, a positive electrode terminal 103, a negative electrode terminal 104, and a safety valve 105. The components included in the secondary battery 100 will be described below.

[0019] As shown in Fig. 2, the secondary battery 100 is formed in a rectangular parallelepiped shape. A positive electrode terminal 103 and a negative electrode terminal 104 are provided on an upper surface 100a of the secondary battery 100 along the stacking direction X. The upper surface 100a corresponds to the upper surface of the secondary battery 100 in Fig. 2. The upper surface 100a is formed in a rectangular shape. The length of the upper surface 100a along the width direction Y of the secondary battery 100 is longer than the length of the upper surface 100a along the stacking direction X of the secondary battery 100.

[0020] The top surface 100a faces the busbar unit 300 shown in FIG. 1 . Two side surfaces 100b along the stacking direction X of the secondary battery 100 face each other perpendicularly to the top surface 100a. The side surfaces 100b are formed in a rectangular shape. The length of the side surfaces 100b along the height direction Z of the secondary battery 100 is longer than the length of the side surfaces 100b along the stacking direction X of the secondary battery 100. The two main surfaces 100c facing the stacking direction X of the secondary battery 100 are in contact with the cell spacers 202 of the holding unit 200, etc.

[0021] The current collector of the secondary battery 100 corresponds to a charge / discharge body to / from which electric power is input / output. The current collector of the secondary battery 100 is configured by winding or stacking a positive electrode and a negative electrode with a separator interposed therebetween. The container 101 contains the current collector and an electrolyte solution.

[0022] The lid 102 seals the current collector and the electrolyte together with the container 101. The lid 102 is joined to the container 101. The positive electrode terminal 103 and the negative electrode terminal 104 relay input and output of electric power between the current collector and the electrical device.

[0023] The positive electrode terminal 103 and the negative electrode terminal 104 are attached to the lid 102. The positive electrode terminal 103 of one secondary battery 100 and the negative electrode terminal 104 of the other secondary battery 100 that are adjacent to each other along the stacking direction X face each other in the stacking direction X, as shown in FIG.

[0024] The safety valve 105 bursts outward from the secondary battery 100 when the internal pressure of the secondary battery 100 exceeds a predetermined value. The safety valve 105 is also referred to as a burst valve. The safety valve 105 is provided, for example, on the lid 102. (Configuration of the Retaining Unit 200) The retaining unit 200 holds multiple secondary batteries 100. As shown in FIG. 2, the retaining unit 200 includes a first end spacer 201, a cell spacer 202, and a second end spacer 203. The retaining unit 200 also includes a first end block 211, a second end block 212, an insulating member 221, and an insert nut 222. As shown in FIG. 1, the retaining unit 200 also includes a first side plate 231, a second side plate 232, and a fastening bolt 241. The components included in the retaining unit 200 will be described below.

[0025] 2 , the first end spacer 201 is provided between the first end block 211 and the secondary battery 100. The first end spacer 201 contacts the first secondary battery 100 located at one end of the 24 stacked secondary batteries 100. The first end spacer 201 insulates the first end block 211 from the secondary battery 100.

[0026] The first end spacer 201 covers each side surface of the first end block 211 and the secondary battery 100 along the width direction Y. The first end spacer 201 covers a portion of the side surface 100b along the stacking direction X of the secondary battery 100. The thickness of the first end spacer 201 along the stacking direction X is sufficiently thinner than the thickness of the secondary battery 100 along the stacking direction X. The first end spacer 201 is made of an insulating material.

[0027] As shown in FIG. 2 , the cell spacers 202 are provided between adjacent secondary batteries 100. The cell spacers 202 hold and insulate the adjacent secondary batteries 100. The cell spacers 202 cover the main surfaces 100c of the adjacent secondary batteries 100 along the width direction Y and a portion of the side surfaces 100b of the adjacent secondary batteries 100 along the stacking direction X. The thickness of the cell spacers 202 along the stacking direction X is sufficiently thinner than the thickness of the secondary batteries 100 along the stacking direction X. The cell spacers 202 are made of an insulating material.

[0028] As shown in Fig. 2, the second end spacer 203 is provided between the secondary battery 100 and the second end block 212. The second end spacer 203 contacts the 24th secondary battery 100 located at the other end of the 24 stacked secondary batteries 100. The second end spacer 203 insulates the secondary battery 100 from the second end block 212. The second end spacer 203 covers each side surface of the first end block 211 and the secondary battery 100 along the width direction Y.

[0029] The second end spacer 203 covers a portion of the side surface 100b along the stacking direction X of the secondary battery 100. The thickness of the second end spacer 203 along the stacking direction X is sufficiently thinner than the thickness of the secondary battery 100 along the stacking direction X. The second end spacer 203 is made of an insulating material.

[0030] 2 , the first end block 211 is stacked with the first secondary battery 100 located at one end of the 24 stacked secondary batteries 100 via a first end spacer 201. The first end block 211 extends along a width direction Y that intersects with the stacking direction X of the secondary batteries 100.

[0031] The first end block 211 is adjacent to the secondary battery 100 located at the end along the stacking direction X and supports the secondary battery 100. The first end block 211 is formed in a rectangular parallelepiped shape extending in the width direction Y. Fastening bolts 241 are screwed into a plurality of screw holes 211m formed in the side surface of the first end block 211 along the width direction Y. As shown in FIG. 1 , the first end block 211 is fixed to the first side plate 231 by the fastening bolts 241.

[0032] Similarly, the first end block 211 is fixed to the second side plate 232 by fastening bolts 241. The first end block 211 has insertion holes 211n formed therein for inserting bolts or the like for fastening the battery pack 1. The first end block 211 is made of, for example, metal or resin.

[0033] 2 , the second end block 212 is stacked with the 24th secondary battery 100 located at the other end of the 24 stacked secondary batteries 100 via a second end spacer 203. The second end block 212 extends along the width direction Y of the secondary batteries 100. The second end block 212 is adjacent to the secondary battery 100 located at the end along the stacking direction X, and supports the secondary battery 100.

[0034] The second end block 212 is formed in a rectangular parallelepiped shape extending in the width direction Y. Fastening bolts 241 are screwed into a plurality of screw holes formed in the side surface of the second end block 212 along the width direction Y. As shown in FIG. 1 , the second end block 212 is fixed to the first side plate 231 by the fastening bolts 241.

[0035] Similarly, the second end block 212 is fixed to the second side plate 232 by fastening bolts 241. The second end block 212 is formed with insertion holes 212n for inserting bolts or the like for fastening the battery pack 1. The second end block 212 is formed of, for example, metal or resin.

[0036] 2, the insulating member 221 is inserted into the first end block 211. The insulating member 221 is also inserted into the second end block 212. The insulating member 221 is formed, for example, in a rectangular parallelepiped shape. The insulating member 221 is made of an insulating material.

[0037] The insulating member 221 may be configured as follows. That is, the insulating member 221 may be molded integrally with the first end spacer 201, or may be molded separately from the first end spacer 201 and then joined to the first end spacer 201. In such a case, the first end block 211 has a recess on the surface facing the first end spacer 201 that accommodates the insulating member 221 along the stacking direction X.

[0038] Similarly, the insulating member 221 may be molded integrally with the second end spacer 203, or may be molded separately from the second end spacer 203 and then joined to the second end spacer 203. In such a case, the second end block 212 has a recess on the surface facing the second end spacer 203 that accommodates the insulating member 221 along the stacking direction X.

[0039] The insert nut 222 is embedded in a recess formed in the upper surface of the insulating member 221. A fastening bolt is anchored to the insert nut 222 via a bus bar that is electrically connected to an external control device, for example.

[0040] 1 , the first side plate 231 is arranged at one end of the stacked secondary batteries 100 in the width direction Y, along the stacking direction X of the stacked secondary batteries 100. The first side plate 231 holds the secondary batteries 100 along the stacking direction X. The first side plate 231 is fixed to the first end block 211 and the second end block 212 by fastening bolts 241.

[0041] 1 , the second side plate 232 is arranged at the other end of the stacked secondary batteries 100 in the width direction Y, along the stacking direction X of the stacked secondary batteries 100. The second side plate 232 holds the secondary batteries 100 along the stacking direction X. The second side plate 232 is fixed to the first end block 211 and the second end block 212 by fastening bolts 241. (Configuration of the busbar unit 300 and the voltage detection unit 400) The configurations of the busbar unit 300 and the voltage detection unit 400 will be described below.

[0042] 3 to 6 are diagrams showing the configurations of the busbar unit 300 and the voltage detection unit 400 according to the first embodiment.

[0043] 3 is a perspective view showing the configuration of the busbar unit 300 and the voltage detection unit 400. FIG.

[0044] Fig. 4 is a diagram of the busbar unit 300 and the voltage detection unit 400 as viewed from the R direction in Fig. 3. It can also be said that Fig. 4 is a diagram of the busbar unit 300 and the voltage detection unit 400 as viewed from the direction opposite to the Z direction. It can also be said that Fig. 4 is a diagram showing the surface of the busbar unit 300.

[0045] Fig. 5 is a diagram of the busbar unit 300 and the voltage detection unit 400 as viewed from the F direction in Fig. 3. It can also be said that Fig. 5 is a diagram of the busbar unit 300 and the voltage detection unit 400 as viewed from the Z direction. It can also be said that Fig. 5 is a diagram showing the back surface of the busbar unit 300.

[0046] FIG. 6 is an enlarged view of a portion indicated by P in FIG.

[0047] As shown in Figures 3 to 6, the bus bar unit 300 includes a first end bus bar 301, a plurality of bus bars 302, a second end bus bar 303, and a bus bar holder 311. As shown in Figures 3 and 4, the voltage detection unit 400 includes a harness 450. The harness 450 is an assembly that brings together the voltage detection terminals 401, the voltage detection line connection portion 402, the connector 403, and the temperature measurement unit.

[0048] The first end bus bar 301 is joined to the positive electrode terminal 103 and the negative electrode terminal 104 (see FIG. 2) of the secondary battery 100 that is closest to the first end block 211 among the 24 stacked secondary batteries 100 .

[0049] The bus bar 302 electrically connects the terminals of the multiple secondary batteries 100. As a result, the bus bar 302 electrically connects one secondary battery 100 to another secondary battery 100 adjacent to each other along the stacking direction X, as shown in Fig. 3. The bus bar 302 joins the positive electrode terminal 103 of one secondary battery 100 adjacent to each other along the stacking direction X to the negative electrode terminal 104 (see Fig. 2) of the other secondary battery 100 adjacent to each other along the stacking direction X.

[0050] The second end bus bar 303 is joined to the negative electrode terminal 104 and the positive electrode terminal 103 of the secondary battery 100 that is closest to the second end block 212 among the 24 stacked secondary batteries 100 .

[0051] The bus bar holder 311 mounts the bus bar 302 and the voltage detection terminal 401. The bus bar holder 311 is provided with mounting areas for the bus bar 302 and the voltage detection terminal 401. The bus bar 302 and the voltage detection terminal 401 are fitted in an overlapping manner into these mounting areas. The bus bar holder 311 is, for example, a resin molded product.

[0052] The voltage detection terminal 401 is disposed on top of the bus bar 302 and joined to the bus bar 302. In this way, the voltage detection terminal 401 detects the voltage of the secondary battery 100.

[0053] The voltage detection line connection portion 402 is joined to the voltage detection terminal 401 and sends information on the voltage detected by the voltage detection terminal 401 to an external control device via the connector 403 .

[0054] The first end bus bar 301, the bus bar 302, the second end bus bar 303, and the voltage detection terminal 401 are formed of, for example, a clad material in which copper and aluminum are bonded together, copper, or aluminum. (Configuration of the bus bar 302 and the voltage detection terminal 401) Figure 7 is a diagram showing the configuration of the bus bar 302 and the voltage detection terminal 401.

[0055] The bus bar 302 is composed of a pair of bus bars 302a and 302b. The bus bars 302a and 302b connect the terminals of the secondary battery 100. In this case, for example, the bus bar 302b is connected to the negative electrode terminal 104 as a terminal. The bus bar 302a is connected to the positive electrode terminal 103 as a terminal.

[0056] Each of the bus bars 302a and 302b has three surfaces: a bottom M1 that is aligned along the XY plane, a side M2 ​​that is bent in the Z direction from the bottom M1 and aligned along the YZ plane, and an upper portion M3 that is bent further in the X direction from the side M2 ​​and aligned along the XY plane. The upper portions M3 of the bus bars 302a and 302b overlap and are electrically joined.

[0057] The voltage detection terminal 401 is joined to each of the first end bus bar 301, the plurality of bus bars 302, and the second end bus bar 303 of the bus bar unit 300. These are joined by, for example, laser welding. The voltage detection terminal 401 is joined to the surface of the bottom portion M1 of the bus bar 302b facing in the opposite direction to the Z direction.

[0058] As shown in FIG. 7, the voltage detection line connection portion 402 connected to the voltage detection terminal 401 is arranged so as to extend from the voltage detection terminal 401 in the direction opposite to the Y direction.

[0059] Furthermore, the bus bar 302b and the voltage detection terminal 401 have positioning portions for more accurate positioning.

[0060] Fig. 8 shows the positioning portion of bus bar 302b, and shows the bus bar 302b as viewed in the opposite direction to the Z direction in Fig. 7. Fig. 9 shows the positioning portion of voltage detection terminal 401, and shows the voltage detection terminal 401 as viewed in the opposite direction to the Z direction in Fig. 7. Note that the voltage detection terminal 401 shown in Fig. 9 is enlarged relative to the bus bar 302b shown in Fig. 8.

[0061] As shown in Fig. 8, recesses 321a and 321b are formed as positioning portions on bus bar 302b. Also, as shown in Fig. 9, recesses 421a and 421b are formed as positioning portions on voltage detection terminal 401. When bus bar 302b and pressure detection terminal 401 are joined together by overlapping each other, recesses 321a and 321b and recesses 421a and 421b are positioned so as to overlap and match each other.

[0062] These positioning portions are arranged so that the positioning portion of busbar 302 and the positioning portion of voltage detection terminal 401 overlap each other when installed in busbar holder 311. In other words, when installed in busbar holder 311, recess 321a and recess 421a are in the same position and overlap each other. Also, recess 321b and recess 421b are in the same position and overlap each other.

[0063] Figure 10 shows a state in which the bus bars 302a, 302b and the voltage detection line terminals 401 are fitted into the bus bar holder 311, and shows the bus bar holder 311, the bus bars 302a, 302b, and the voltage detection terminals 401 as viewed from the direction IV in Figure 3 in the direction opposite to the Z direction in Figure 7. Figure 11 shows a state in which the voltage detection terminals 401 are arranged in the bus bar holder 311, and shows the bus bar holder 311 and the voltage detection terminals 401 as viewed from the direction V in Figure 3 in the Z direction in Figure 7. Note that the bus bar holder 311 is depicted semi-transparent in Figure 11 to facilitate understanding.

[0064] The bus bar holder 311 has positioning portions that engage with the positioning portions of the bus bar 302 and the voltage detection terminal 401 and determine the positions of the bus bar 302 and the voltage detection terminal 401. The positioning portions of the bus bar holder 311 are protrusions 331 a and 331 b, as shown in FIGS.

[0065] That is, recesses 321a and 421a, which are positioning portions for busbar 302 and voltage detection terminal 401, engage with protrusions 331a, which are positioning portions for busbar holder 311. Meanwhile, recesses 321b and 421b, which are positioning portions for busbar 302 and voltage detection terminal 401, engage with protrusions 331b, which are positioning portions for busbar holder 311. In this way, the positioning portions for busbar 302 and voltage detection terminal 401 and the positioning portion for busbar holder 311 have complementary shapes. This allows busbar 302b and voltage detection terminal 401 to be positioned in busbar holder 311 with greater precision.

[0066] 11 , a joint 340 that joins bus bar 302 b and voltage detection terminal 401 is provided between recesses 421 a and 421 b, which are positioning portions of voltage detection terminal 401. Joint 403 is provided at a position where bus bar 302 b and voltage detection terminal 401 overlap. As described above, the joining is performed by, for example, laser welding, and therefore, in this case, joint 340 is a laser welding mark.

[0067] Since voltage detection terminal 401 is connected to bus bar 302b by laser welding, it is desirable to limit the joint between voltage detection terminal 401 and bus bar 302b to a narrow area for the sake of miniaturization. To perform laser welding within this limited area, it is necessary to prevent voltage detection terminal 401 from shifting.

[0068] Therefore, as described above, by forming positioning portions (which have complementary shapes) on the bus bar 302b and the voltage detection terminal 401 and on the bus bar holder 311, the bus bar 302b and the voltage detection terminal 401 can be positioned with greater precision on the bus bar holder 311. By forming positioning portions on the bus bar 302b and the voltage detection terminal 401 in this way, the voltage detection terminal 401 can be positioned with high precision relative to the bus bar 302b.

[0069] However, when the bus bar 302b is assembled, it is anticipated that a problem may occur in which the recess 421a side of the voltage detection terminal 401 becomes detached from the bus bar holder 311 due to the bus bar 302b, as shown by the dashed arrow ALW in Figure 7.

[0070] 11, the recessed portion 421a of the voltage detection terminal 401 can freely move toward the front side of the page and come off from the protruding portion 331a, which is the positioning portion of the bus bar holder 311. The recessed portion 421b of the voltage detection terminal 401 is supported by the voltage detection line connecting portion 402 and therefore does not move much.

[0071] Therefore, when the bus bar 302b is assembled and laser-welded to the voltage detection terminal 401, if the recess 421a side of the voltage detection terminal 401 is tilted toward the front side of the paper, the laser welding cannot be performed properly, resulting in a problem of poor welding.

[0072] For this reason, it is required to have a structure in which at least the recessed portion 421 a side of the voltage detection terminal 401 does not come off the positioning protrusion 331 a of the bus bar holder 311 .

[0073] Next, the present invention for solving the above-mentioned problems will be described.

[0074] The present invention is characterized in that a positioning convex portion of the busbar holder is provided with a positioning maintaining portion (stopper portion) that contacts the non-welding surface of the voltage detection terminal opposite to the welding surface to be welded to the busbar. In other words, when the busbar is assembled, the positioning maintaining portion prevents movement of the end face of the voltage detection terminal. The laser beam is irradiated toward the non-welding surface as shown in Figure 11.

[0075] As a result, even if the concave side of the end face of the voltage detection terminal moves to come off the positioning protrusion of the bus bar holder, the positioning position maintaining portion restricts the movement of the concave side of the voltage detection terminal, allowing for good laser welding.

[0076] Next, a first embodiment of the present invention will be described in detail with reference to FIGS.

[0077] 12 shows a state in which positioning protrusions 331b and 331a formed on bus bar holder 311 are engaged with positioning recesses 421b and 421a formed on voltage detection terminal 401. Note that Fig. 12 shows the state before bus bar 302b is installed.

[0078] FIG. 13 shows the voltage detection terminal 401 in a separated state before being assembled into the bus bar holder 311.

[0079] 12 and 13, the voltage detection terminals 401 are formed in the shape of a long rectangle having opposing long sides Ls and opposing short sides Ss. A voltage detection line connection portion 402 is formed on one end surface of the voltage detection terminals 401 so as to extend in a direction perpendicular to the long sides Ls.

[0080] Here, one flat surface of the voltage detection terminal 401 (the surface visible in the drawing) is a welding surface 401ms to which the bus bar 302b is welded. Conversely, the flat surface opposite to the welding surface 401ms is a non-welding surface 401nm (see FIG. 14). As described above, the laser beam in laser welding is irradiated from the non-welding surface 401nm.

[0081] The ratio of the short side Ss to the long side Ls of the voltage detection terminal 401 is set to a range of 0.5 to 2.0. The long side Ls of the voltage detection terminal 401 is shorter than the length in the long side direction of the bus bar 302b to be joined, and is set to a range of 0.3 to 0.8 of the length in the long side direction of the bus bar 302b.

[0082] A recess 421b is formed on the short side Ss on the side of the voltage detection line connection portion 402, and serves as a positioning portion for the voltage detection terminal 401. The recess 421b is a rectangular notch formed by punching along the long side Ls.

[0083] Furthermore, a wall portion 311w forming the bus bar holder 311 is formed with a protrusion 331b facing the short side Ss, having a shape complementary to the shape of the recess 421b, and serving as a positioning portion for the bus bar holder 311. The protrusion 331b extends perpendicularly from the wall portion 311w and is a protrusion whose cross section along the long side Ls is rectangular.

[0084] Therefore, positioning can be performed by engaging the recessed portions 421b of the voltage measurement terminals 401 with the protruding portions 331b of the bus bar holder 311. This positioning method is the same as that shown in FIG.

[0085] On the other hand, as shown in FIG. 13 , a recess 421c that serves as a positioning portion for the voltage detection terminal 401 is formed on the short side Ss opposite the voltage detection line connection portion 402. The recess 421c is formed by a rectangular first notch 421c1 along the long side Ls and a rectangular second notch 421c2 that is formed continuous with the first notch 421c1 and along the short side Ss. Therefore, the overall shape of the recess 421c is a "T" shape. Therefore, the length L5 of the recess 421c2 along the short side Ss is longer than the length L4 of the recess 421c1 along the short side Ss when viewed from a direction perpendicular to the welding surface 401ms.

[0086] Furthermore, a wall portion 311w forming the bus bar holder 311 is formed with a protrusion 331c facing the short side Ss, having a shape complementary to the shape of the recess 401c, and serving as a positioning portion for the bus bar holder 11. The protrusion 331c extends so as to protrude vertically from the wall portion 331w, and has a T-shaped cross section along the long side Ls.

[0087] In other words, the convex portion 331c is formed from a first convex portion 331c1 (see Figure 13) having a rectangular cross section along the long side Ls, and a second convex portion 331c2 (see Figure 13) that is formed continuously with the first convex portion 331c1 and has a rectangular cross section along the short side Ss.

[0088] Therefore, the overall shape of the protrusion 331c is a "T" shape. As a result, the length of the protrusion 331c2 in the direction of the short side Ss is longer than the length of the protrusion 331c1 in the direction of the short side Ss when viewed from a direction perpendicular to the welding surface 401ms. This length relationship is the same as that of the recess 421c.

[0089] Therefore, the recessed portions 421c of the voltage detection terminals 401 can be engaged with the protruding portions 331c of the bus bar holder 311 to perform positioning.

[0090] Here, a key portion 421d that engages with the first convex portion 331c1 is formed on the short side Ss of the voltage detection terminal 401 opposite the voltage detection line connection portion 402. This key portion 421d has the function of preventing the voltage detection terminal 401 from slipping out in the long side direction. Therefore, when fitting the voltage detection terminal 401 into the bus bar holder 311, it is sufficient to insert the concave portion 421c of the voltage detection terminal 401 from above the convex portion 331c of the bus bar holder 311 to engage it.

[0091] Furthermore, a positioning maintaining portion 341, which is a feature of this embodiment, is formed on a part of the protrusion 331c. This positioning maintaining portion 341 functions as a stopper that prevents the voltage detection terminal 401 from coming off in the direction in which the protrusion 331c extends. In other words, as shown in Fig. 12, it acts to prevent the end face of the voltage detection terminal 401 on the side of the recess 421a (the side opposite the voltage detection line connection portion 402) from moving backward into the page when it is incorporated into the bus bar holder 311.

[0092] The positioning position maintaining unit 341 will be described in further detail with reference to Figures 13, 14, and 15. Figure 14 shows a cross section taken along line A-A in Figure 12, and Figure 15 shows a state in which the voltage detection terminal 401 is incorporated into the bus bar holder 311 but before the bus bar 302 is incorporated.

[0093] 13 to 15, the positioning maintaining portion 341 is a plate-like protruding portion that, like the convex portion 331c, extends perpendicularly to the wall portion 331w of the bus bar holder 311. In other words, the positioning maintaining portion 341 is a plate-like protruding portion that has a stopper function and protrudes in a direction perpendicular to the direction in which the convex portion 311c extends along the wall portion 311w (toward the rear in the drawings).

[0094] The length L1 of the protruding portion 331c and the length L2 of the protruding portion of the positioning maintaining portion 341 are set to be the same or approximately the same. However, in the drawings, the length L1 is set to be slightly longer. Furthermore, the length L3 of the positioning maintaining portion 341 in the direction along the wall portion 311w is set to be a length that includes the protruding portion 331c. In the drawings, it is set to be longer than the length of the protruding portion 331c2.

[0095] In short, the positioning position maintaining portion 341 only needs to have an area large enough to receive the end face of the voltage detection terminal 401 opposite the voltage detection line connection portion 402 when the voltage detection terminal 401 is incorporated into the bus bar holder 311.

[0096] Figure 14 shows a cross section taken along line A-A in Figure 12. As can be seen from this figure, the positioning maintaining portion 341 is formed on the end surface of the protrusion 331c, in this case the lower end portion. Here, the lower end portion is the portion where the voltage detection terminal 401 and the bus bar 302b overlap. Note that in Figure 12, the bus bar 302b has not yet been overlapped, so it is shown by a dashed line in Figure 14.

[0097] Furthermore, the positioning maintaining portion 341 is configured to come into contact with a non-welding surface 401nm opposite to the welding surface 401ms of the voltage measurement terminal 401 that is welded to the bus bar 302b. Therefore, when the end surface of the voltage measurement terminal 401 on the side of the recess 421a is incorporated into the bus bar holder 311, the end surface of the voltage measurement terminal 401 on the side of the recess 421a can be prevented from moving downward.

[0098] As shown in Figures 14 and 15, after the voltage detection terminal 401 is incorporated into the bus bar holder 311, the bus bar 302b is overlapped and then a laser beam LB is irradiated from the non-welding surface 401 nm, thereby welding the voltage detection terminal 401 and the bus bar 302b.

[0099] A reinforcing rib may be formed along the long side Ls on the surface of the voltage detection terminal 401. For example, as shown by the dashed line in Fig. 14, a reinforcing rib 401tk may be formed on the non-welding surface 401nm of the voltage detection terminal 401, protruding from this surface. This prevents deformation of the voltage detection terminal 401, enabling highly accurate alignment.

[0100] As described above, in this embodiment, the voltage measuring terminal has a voltage measuring terminal-side positioning portion, the bus bar holder has a bus bar holder-side positioning portion that engages with the voltage measuring terminal-side positioning portion to determine the position of the voltage measuring terminal, and the bus bar holder-side positioning portion is formed with a positioning maintaining portion that contacts the non-welding surface of the voltage measuring terminal on the side opposite to the welding surface that is welded to the bus bar. This makes it possible to position the voltage measuring terminal with respect to the bus bar with high precision and to reliably maintain the position.

[0101] Next, a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in that two positioning maintaining portions are provided so as to sandwich the voltage detection terminal therebetween.

[0102] 16 and 17, the voltage detection terminal 401 has the same configuration as the voltage detection terminal shown in Fig. 9. A recess 421a, which serves as a positioning portion, is formed on the short side Ss of the voltage detection terminal 401 opposite to the voltage detection line connection portion 402. This recess 421a is a rectangular notch that extends along the long side Ls.

[0103] Furthermore, the convex portions 331a formed on the bus bar holder 311 are rectangular protrusions formed in a shape complementary to the shape of the concave portions 421a. Therefore, by inserting the voltage detection terminals 401 along the long side direction, the concave portions 421a of the voltage detection terminals 401 and the convex portions 331a of the bus bar holder 311 can be engaged with each other to achieve positioning.

[0104] 17, a positioning maintaining portion 341 is formed near the lower end of the protruding portion 331a. This positioning maintaining portion 341 is the same as that in the first embodiment. Meanwhile, above the positioning maintaining portion 341, another positioning maintaining portion 342 is formed on the protruding portion 331a.

[0105] The length G between the positioning maintaining portions 341 and 342 is set to be longer than the thickness of the voltage detection terminal 401. In other words, the length G between the positioning maintaining portions 341 and 342 is set to a length that allows for some movement in a direction perpendicular to the insertion direction when the voltage detection terminal 401 is inserted.

[0106] The positioning position maintaining unit 341 has the function of preventing the voltage detection terminal 401 from moving toward the non-welding surface 401nm side of the voltage detection terminal 401 (the lower side in the drawing), and the positioning position maintaining unit 342 has the function of preventing the voltage detection terminal 401 from moving toward the welding surface 401ms side of the voltage detection terminal 401 (the upper side in the drawing).

[0107] Here, the protrusion length of the positioning maintaining portion 342 from the wall portion 311w of the bus bar holder 311 is longer by ΔGp than the protrusion length of the positioning maintaining portion 341 from the wall portion 311w of the bus bar holder 311. This length ΔGp provides the positioning maintaining portion 342 with a stopper function.

[0108] In other words, when the recess 421a of the voltage detection terminal 401 is inserted into the protrusion 321a of the bus bar holder 311, the positioning position maintaining portion 342 extends beyond the recess 421a of the voltage detection terminal 401 and reaches the welding surface 401ms, and the stopper function is activated at this portion.

[0109] It is also possible to provide a positioning position maintaining unit having the same shape as the positioning position maintaining unit 341 shown in Fig. 16 instead of the positioning position maintaining unit 342. In the second embodiment, the positioning position can be maintained more reliably than in the first embodiment.

[0110] Next, a third embodiment of the present invention will be described. The third embodiment differs from the second embodiment in that a bent portion is formed on the short side of the voltage detection terminal, extending along the wall portion of the bus bar holder, and this bent portion is in contact with the wall portion.

[0111] 18 and 19, the shape of the convex portion 321a formed on the wall portion 311w of the bus bar holder 311 is similar to the concept of the second embodiment, and positioning position maintaining portions 341 and 342 are provided at two locations on the convex portion 321a.

[0112] In contrast, the voltage detection terminal 401 has a different configuration from the voltage detection terminal shown in Fig. 9. A recess 421a, which serves as a positioning portion, is formed on the short side Ss of the voltage detection terminal 401 opposite to the voltage detection line connection portion 401. This recess 421a is a rectangular notch that extends along the long side Ls.

[0113] The region between the long side Ls on the voltage detection wire connection portion 402 side and the notch is formed longer in the long side direction than the region between the other long side and the notch. This elongated region is bent toward the welding surface 401ms side (upper side in the drawing) to form bent portions 422a and 422b. Note that Figure 18 is a view looking into the depths of the paper, with the line connecting the bent portions 422a and 422b as the boundary.

[0114] Furthermore, the convex portions 331a formed on the bus bar holder 311 are rectangular protrusions formed in a shape complementary to the shape of the concave portions 421a. Therefore, by inserting the voltage detection terminals 401 along the long side direction, the concave portions 421a of the voltage detection terminals 401 and the convex portions 331a of the bus bar holder 311 can be engaged with each other to achieve positioning.

[0115] However, in this state, the bent portions 422 a and 422 b of the voltage detection terminal 401 are arranged so as to contact the wall surface of the wall portion 311 w of the bus bar holder 311 .

[0116] In this way, the bent portions 422a, 422b of the voltage detection terminal 401 are arranged so as to contact the wall portion 311w of the bus bar holder 311, thereby enabling stable positioning. Furthermore, the large areas of the bent portions 422a, 422b increase the fixing force, thereby improving the positioning accuracy. In the third embodiment, the positioning can be maintained more reliably than in the second embodiment.

[0117] As described above, the present invention is characterized in that it comprises a busbar, a voltage detection terminal welded to the busbar, and a busbar holder provided with mounting areas for the busbar and the voltage detection terminal, wherein the voltage detection terminal has a voltage detection terminal-side positioning portion, and the busbar holder has a busbar holder-side positioning portion that engages with the voltage detection terminal-side positioning portion to determine the position of the voltage detection terminal, and a positioning position maintaining portion that contacts the non-welded surface opposite to the welded surface of the voltage detection terminal that is welded to the busbar is formed on the busbar holder-side positioning portion.

[0118] This makes it possible to provide a secondary battery and a battery pack in which the voltage detection terminals can be positioned with high precision relative to the bus bars and the positioned positions can be reliably maintained.

[0119] The present invention is not limited to the above-described embodiments, but includes various modifications. The above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace other configurations with respect to the configuration of each embodiment.

[0120] 1... battery pack, 200... holding unit, 300... busbar unit, 302, 302a, 302b... busbar, 311... busbar holder, 421a, 421b, 421c... recessed portion (positioning portion), 331a, 331b, 331c... protruding portion (positioning portion), 340... joint portion, 341... positioning position maintaining portion, 342... second positioning position maintaining portion, 400... voltage detection unit, 401... voltage detection terminal, 402... voltage detection line connection portion.

Claims

1. A secondary battery comprising: a bus bar that electrically connects battery terminals; a voltage detection terminal that is arranged on top of and joined to the bus bar; and a bus bar holder that is provided with a mounting area for the bus bar and the voltage detection terminal, wherein the voltage detection terminal has a voltage detection terminal side positioning portion, and the bus bar holder has a bus bar holder side positioning portion that engages with the voltage detection terminal side positioning portion to determine the position of the voltage detection terminal, and a positioning position maintaining portion that contacts the non-joint surface of the voltage detection terminal on the side opposite to the joint surface that is joined to the bus bar is formed on the bus bar holder side positioning portion.

2. A secondary battery according to claim 1, wherein the voltage detection terminal side positioning portion is a recess formed on the end face of the voltage detection terminal, and the bus bar holder side positioning portion is a protrusion formed on the wall of the bus bar holder.

3. A secondary battery according to claim 2, wherein the voltage detection terminals are rectangular with long sides facing each other and short sides facing each other, the recesses being formed on the short sides, and the protrusions of the bus bar holder being formed on the wall of the bus bar holder facing the short sides.

4. A secondary battery according to claim 3, wherein the positioning position maintaining portion is a plate-shaped protrusion extending from the wall portion of the bus bar holder and contacting the non-joint surface of the voltage detection terminal.

5. A secondary battery according to claim 4, wherein the positioning maintaining portion is formed on a part of the protrusion formed on the wall portion of the bus bar holder.

6. A secondary battery according to claim 5, wherein the positioning position maintaining portion is formed on the end face of the protrusion formed on the wall portion of the bus bar holder.

7. A secondary battery according to claim 6, characterized in that the length of the positioning position maintaining portion extending from the wall portion of the bus bar holder and the length of the protruding portion extending from the wall portion of the bus bar holder are set to the same length.

8. A secondary battery as described in claim 3, wherein the recess formed in the voltage detection terminal is formed from a first notch along the long side and a second notch formed continuously with the first notch and along the short side, and the protrusion formed on the wall of the bus bar holder is formed from a first protrusion and a second protrusion having shapes complementary to the shapes of the first notch and the second notch.

9. A secondary battery according to claim 8, wherein the length of the second cutout in the short side direction is set to be longer than the length of the first cutout in the short side direction.

10. A secondary battery as described in claim 9, characterized in that the end face of the voltage detection terminal that forms the first notch of the recess has a key portion formed thereon that engages with the first protrusion of the protrusion.

11. A secondary battery as described in claim 2, characterized in that in addition to the positioning maintaining portion, a second positioning maintaining portion that contacts the joint surface of the voltage detection terminal is formed on the bus bar holder side positioning portion.

12. A secondary battery according to claim 11, wherein the second positioning position maintaining portion is formed on the protrusion formed on the wall portion of the bus bar holder.

13. A secondary battery according to claim 11, wherein the second positioning maintaining portion is a plate-like protruding portion extending from the wall portion of the bus bar holder.

14. A secondary battery as described in claim 3, wherein the area between one of the long sides and the recess is extended in a direction along the long side, and the extended portion is folded back along the wall portion to form a bent portion, and the bent portion is in contact with the wall portion.

15. A secondary battery as claimed in claim 3, wherein the ratio of the short side to the long side of the voltage detection terminal is set within the range of 0.5 to 2.0, or the long side of the voltage detection terminal is formed to be shorter than the length of the long side of the bus bar to which it is joined, and is set within the range of 0.3 to 0.8 of the length of the long side of the bus bar.

16. A secondary battery according to claim 3, wherein the voltage detection terminal has a rib formed along the long side thereof that protrudes from the surface of the voltage detection terminal.

17. An assembled battery comprising a plurality of secondary batteries and a bus bar that electrically connects the terminals of the plurality of secondary batteries, wherein the secondary batteries are the secondary batteries described in any one of claims 1 to 16.