Battery pack

Abstract

This battery pack comprises: a plurality of battery blocks in which block through-holes passing through a pair of block main surfaces are opened on each of the block main surfaces; a plurality of heat radiation plates in which plate opening holes are opened at positions facing the end surfaces of the block through-holes between adjacent battery blocks; a plurality of heat radiation tubes each of which is inserted into each of the block through-holes and in which a tube through-hole is formed; and a connection shaft that is inserted into the series of tube through-holes while the heat radiation tubes are arranged in coaxial orientations on front and rear surfaces of the plurality of heat radiation plates so that each of the tube through-holes in the front and rear surfaces communicate via the plate opening holes, the connection shaft connecting the plurality of battery blocks via the series of heat radiation tubes while the heat radiation tubes and the heat radiation plates are thermally coupled.

Description

Battery pack

[0001] The present disclosure relates to a battery pack.

[0002] Battery packs that connect multiple rechargeable secondary battery cells, such as lithium-ion secondary batteries, to power electrical devices are used for a variety of purposes (see, for example, Patent Document 1). In such battery packs, as the number of secondary battery cells used increases, it becomes necessary to stack multiple battery blocks, each connecting multiple secondary battery cells. However, because secondary battery cells generate heat during charging and discharging, it is necessary to efficiently dissipate the heat from the battery pack to the outside.

[0003] However, in a battery pack in which battery blocks are stacked in multiple stages, it is not easy to efficiently dissipate heat to the outside. In particular, the battery blocks sandwiched between the heat-generating battery blocks tend to trap heat internally, and unlike the battery blocks located at the ends, these blocks have almost no exposed surfaces that can dissipate heat, making heat dissipation difficult. For this reason, adding a structure for heat dissipation could be considered, but given the demand for smaller and cheaper battery packs, this is not easy to achieve.

[0004] Furthermore, in a configuration in which battery blocks are stacked in multiple stages, the connection strength between the battery blocks is required, and a structure for such fixing is also required.

[0005] JP 2012-89478 A

[0006] One object of the present disclosure is to provide a battery pack with improved heat dissipation. Another object is to provide a battery pack with improved connection strength in a structure in which multiple battery blocks are stacked. Note that the description of these objects and objects of the present disclosure does not preclude the existence of other objects and objects. Furthermore, it is not necessary for one embodiment of the present disclosure to solve all of these objects. Furthermore, other objects can be extracted from the description of the specification, drawings, and claims of the present disclosure.

[0007] A battery pack according to one embodiment of the present disclosure includes: a plurality of battery blocks including a plurality of secondary battery cells, each having a pair of block main surfaces and block end surfaces intersecting the pair of block main surfaces, with end faces of block through holes penetrating the pair of block main surfaces opening in each block main surface; a plurality of heat dissipation plates arranged between the opposing block main surfaces of adjacent battery blocks among the plurality of battery blocks, each having a plate opening hole at a position facing the end face of the block through hole; a plurality of heat dissipation tubes having tube through holes formed therein that are inserted into each of the block through holes; and connecting shafts that are inserted into a series of tube through holes with the heat dissipation tubes arranged coaxially on the front and back of the plurality of heat dissipation plates so that the tube through holes on the front and back are connected via the respective plate opening holes, and that connect the plurality of battery blocks to the heat dissipation plates in a thermally coupled state via the series of heat dissipation tubes.

[0008] According to a battery pack according to one embodiment of the present disclosure, multiple battery blocks are connected by connecting shafts, heat dissipation tubes are placed in the block through-holes that penetrate each battery block, and heat dissipation plates are interposed at the interfaces between the battery blocks, making it possible to efficiently dissipate heat from the inside of the battery blocks and the interfaces between the battery blocks, where heat tends to build up, via the thermally coupled heat dissipation tubes and heat dissipation plates.

[0009] 1 is a perspective view showing a battery pack according to a first embodiment. It is an exploded perspective view of the battery pack of FIG. 1. It is a vertical cross-sectional view taken along line III-III of FIG. 1. It is a vertical cross-sectional view taken along line IV-IV of FIG. 1. It is an exploded perspective view showing the battery blocks of the core block of FIG. 2 in an exploded state. It is an exploded perspective view showing the first battery block of the core block of FIG. 2 in an exploded state. It is an exploded perspective view of the core block of FIG. 5 as seen from the rear side. It is a further exploded perspective view of the core block of FIG. 5. It is an exploded perspective view showing the heat dissipation plate, heat dissipation sheet, fireproof sheet, and lead plate at the interface between the first battery block and the second battery block of the core block of FIG. 2 in an exploded state. It is a further exploded perspective view of the core block of FIG. 8. It is an enlarged cross-sectional view of the area surrounded by a dashed line in the battery pack of FIG. 3. It is a vertical cross-sectional view showing the heat dissipation path of the battery pack of FIG. 3. It is an enlarged perspective view showing the connection structure of the lead plate.

[0010] The embodiments of the present disclosure may be specified by the following configurations and features.

[0011] In a battery pack according to another aspect of the present disclosure, in the above aspect, the plurality of battery blocks are arranged with the block main surfaces perpendicular to the connecting shaft, and the block through-holes are opened in the block main surfaces so as to be spaced apart in a first direction perpendicular to the connecting shaft. With the above configuration, block through-holes are formed in multiple locations in each battery block, making it possible to efficiently cool the interior of the battery block from multiple locations that are separated from each other.

[0012] In a battery pack according to another aspect of the present disclosure, in any of the above aspects, the plurality of battery blocks have the block through-holes opened along the edge of the main surface of the block, and the plurality of block through-holes are spaced apart from one another. With this configuration, the surface of each battery block can be cooled from multiple locations that are spaced apart from one another by forming multiple block through-holes on the surface side of each battery block.

[0013] In a battery pack according to another aspect of the present disclosure, in any of the above aspects, the heat dissipation plate and the heat dissipation tube are each made of metal. With this configuration, the heat dissipation plate and the heat dissipation tube made of metal with high thermal conductivity can be used to improve the heat dissipation performance of the battery block.

[0014] In yet another aspect of the battery pack of the present disclosure, in any of the above aspects, the battery pack further includes a thermally conductive exterior case that houses a core block formed by joining the plurality of battery blocks, and the exterior case is fastened to the connecting shaft while being in thermally coupled contact with a heat dissipation tube that is exposed at the end face of the block through hole in the block main surface that constitutes one face of the core block. With the above configuration, by fastening the connecting shaft to the exterior case with excellent thermal conductivity, heat can be conducted to the exterior case via the heat dissipation tube, further improving heat dissipation.

[0015] In a battery pack according to still another aspect of the present disclosure, in any of the above aspects, the exterior case is divided into a first case and a second case, and the second case has a screw boss formed therein that abuts against the tip of the connecting shaft and the open end of the heat dissipation tube surrounding the tip of the connecting shaft. With the above configuration, the second case is joined to the heat dissipation tube and the connecting shaft via the screw boss, and heat is conducted to the exterior case side through these, enabling improved heat dissipation.

[0016] In a battery pack according to still another aspect of the present disclosure, in any of the above aspects, the second case is formed of a metal case, and this configuration allows heat from the core block to be efficiently dissipated to the outside via the metal second case.

[0017] Furthermore, in a battery pack according to another embodiment of the present disclosure, in any of the above embodiments, the plurality of battery blocks include a first battery block, a second battery block arranged on a block main surface of the first battery block, and a third battery block arranged on a block main surface of the second battery block, and the block main surface of the third battery block is formed larger than the block main surface of the second battery block.

[0018] In addition, a battery pack according to another aspect of the present disclosure is any of the above-described aspects, further including an insulating and flexible heat-dissipating sheet disposed at the interface between the heat-dissipating plate and the main surface of the battery block. With this configuration, the heat-dissipating plate and the battery block are insulated from each other, and by interposing the flexible heat-dissipating sheet at the interface between the heat-dissipating plate and the battery block, it is possible to prevent gaps from occurring at the interface, enhance thermal bonding, and improve thermal conductivity.

[0019] In addition, a battery pack according to another aspect of the present disclosure may further include a fire-resistant sheet disposed at the interface between the heat dissipation plate and the main surface of the battery block in a position that does not overlap the heat dissipation sheet. With this configuration, even if a secondary battery cell in one of the battery blocks catches fire, the fire-resistant sheet prevents the flame from reaching the battery block on the opposite side of the heat dissipation plate, thereby enhancing safety.

[0020] In a battery pack according to another aspect of the present disclosure, in any of the above aspects, each of the plurality of secondary battery cells has a gas exhaust port on one of its cell end faces for exhausting gas when internal pressure increases, and the fire-resistant sheet is positioned opposite one of the cell end faces of the secondary battery cell. With this configuration, by arranging the fire-resistant sheet, which is positioned so as not to overlap with the heat-dissipating sheet, opposite the cell end face with the gas exhaust port, even if high-temperature, high-pressure gas is exhausted from the gas exhaust port, the fire-resistant sheet can prevent a flame from reaching the battery block side opposite the heat-dissipating plate.

[0021] In addition, in a battery pack according to another aspect of the present disclosure, in any of the above aspects, a step is formed on the end face of the heat dissipation tube, and the heat dissipation sheet and the fire-resistant sheet each have an opening or a bypass around the portion where the heat dissipation tube is arranged. This configuration prevents the heat dissipation sheet and the fire-resistant sheet from interfering with thermal bonding at the joint interface between the heat dissipation tube and the heat dissipation plate.

[0022] In addition, a battery pack according to another aspect of the present disclosure is any of the above-described aspects, further including lead plates disposed on the main surfaces of the battery blocks and connecting the plurality of secondary battery cells, and bus bars connected to the lead plates at the outer edges of the heat dissipation plates. With this configuration, the heat dissipation plates are interposed between the battery blocks, and electrical connection between the battery blocks can be achieved by bypassing the heat dissipation plates via the bus bars around the heat dissipation plates.

[0023] In a battery pack according to still another aspect of the present disclosure, in any of the above aspects, the heat dissipation plate has plate notches formed at its edge, and the bus bars are disposed in the plate notches. This configuration makes it easy to position and arrange the bus bars on the edge of the lead plates.

[0024] In addition, a battery pack according to another aspect of the present disclosure is any of the above-described aspects, further including a metal current collector plate that is thicker than the lead plate and is laminated on the lead plate, and the bus bar is connected to the current collector plate. With this configuration, by laminating a thicker current collector plate on the lead plate, it is possible to pass a large current through the lead plate and connect it to the bus bar.

[0025] In a battery pack according to another aspect of the present disclosure, in any of the above aspects, the heat dissipation tubes are arranged in the same orientation as the plurality of secondary battery cells. With this configuration, the heat dissipation tubes can be positioned so as not to get in the way within the battery block.

[0026] Embodiments of the present disclosure will be described below with reference to the drawings. However, the embodiments described below are merely examples for embodying the technical concepts of the present disclosure, and the present disclosure is not limited to the following. Furthermore, this specification does not in any way specify the components set forth in the claims to be those of the embodiments. The dimensions, materials, shapes, relative positions, etc. of components described in the embodiments are not intended to limit the scope of the present disclosure, and are merely illustrative examples, unless otherwise specified. The size and positional relationships of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate components that are identical or of the same quality, and detailed descriptions will be omitted as appropriate. Furthermore, the elements constituting the present disclosure may be configured with the same components, such that multiple elements are shared by one component, or conversely, the functions of one component may be shared by multiple components.

[0027] The battery pack of the present disclosure can be used as a driving power source for mobile objects such as electric carts, electric scooters, and assisted bicycles, as a power source for portable electrical devices such as radios, electric cleaners, and power tools, as a backup power source for servers in stationary power storage applications, as a power supply device for home, office, or factory use, and as a driving power source for vehicles such as hybrid cars and electric automobiles. Hereinafter, a battery pack used as a driving power source for an electric motorcycle will be described as one embodiment of the present invention.

[0028] [Embodiment 1] A battery pack 100 according to Embodiment 1 of the present disclosure is shown in Figures 1 to 13. In these figures, Figure 1 is a perspective view showing the battery pack 100 according to Embodiment 1, Figure 2 is an exploded perspective view of the battery pack 100 of Figure 1, Figure 3 is a vertical cross-sectional view taken along line III-III of Figure 1, Figure 4 is a vertical cross-sectional view taken along line IV-IV of Figure 1, Figure 5 is an exploded perspective view showing the core block 2 of Figure 2 in an exploded state in which each battery block 20 is separated, Figure 6 is an exploded perspective view showing the core block 2 of Figure 2 in an exploded state in which the first battery block 21 is separated, Figure 7 is an exploded perspective view of the core block 2 of Figure 5 as seen from the rear side, and Figure 8 is an exploded perspective view of the core block 2 of Figure 5 in an exploded state in which the first battery block 21 is separated. Fig. 9 is an exploded perspective view of the core block 2 in Fig. 2, showing the heat dissipation plate 30, heat dissipation sheet 60, fireproof sheet 70, and lead plate 4 at the interface between the first battery block 21 and the second battery block 22, Fig. 10 is a further exploded perspective view of the core block 2 in Fig. 8, Fig. 11 is an enlarged cross-sectional view of the area surrounded by a dashed line in the battery pack 100 in Fig. 3, Fig. 12 is a vertical cross-sectional view showing the heat dissipation path HP of the battery pack 100 in Fig. 3, and Fig. 13 is an enlarged perspective view showing the connection structure of the lead plates. The battery pack 100 shown in these figures includes an outer case 10 and a core block 2.

[0029] (External Case 10) The external case 10 is a component for storing the core block 2. The external shape of the external case 10 can be any shape that has an internal storage space. In the example shown in Figures 1 to 3, the external case 10 has a boot-like appearance with a larger bottom. However, the external case is not limited to this shape, and can have any shape, such as a rectangular parallelepiped, a cubic, or other prismatic shape, a cylindrical shape, or an elliptical cylindrical shape.

[0030] The outer case 10 is divided into multiple parts. In the example shown in FIG. 2 , the outer case 10 is divided vertically into a first case 11 and a second case 12. The first case 11 is a rectangular column with an open bottom, with its lower portion protruding forward, creating a connected internal space. The first case 11 also has an open cylindrical top, which is closed by a lid 14. The lid 14 and the first case 11 are connected by threading a joint formed around the top open end. This configuration is not limited to this, and the lid and the first case may be molded integrally. Meanwhile, the second case 12 is tub-shaped, with an open top that matches the opening on the bottom of the first case 11. A screw boss 16 is formed on the bottom of the opening to secure the second case 12 to the core block 2. The screw boss 16 has a thread groove that threads onto the tip of a connecting shaft 50, which will be described later.

[0031] 2 to 4, an internal space is formed inside the exterior case 10 to house the core block 2. The first case 11 and the second case 12 each have an opening at their joint surface, and house the core block 2 sandwiched between them. The first case 11 and the second case 12 are joined by screwing together the joint surfaces formed around the open ends.

[0032] The second case 12 is made of a material that is rigid and thermally conductive. Preferably, it is made of a metal such as aluminum, magnesium, zinc, iron, or stainless steel. In the example of FIG. 2, the first case 11 is made of polycarbonate resin, which has excellent formability. Heat from the core block 2 can be efficiently dissipated to the outside via the metal second case 12 (details will be described later).

[0033] (Core block 2) As shown in Figures 2 to 4, the core block 2 is housed inside the exterior case 10. The core block 2 is made up of multiple battery blocks 20. The core block 2 is made up of multiple battery blocks 20, multiple heat dissipation plates 30, multiple heat dissipation tubes 40, and multiple connecting shafts 50. The multiple battery blocks 20 are connected in a multi-tiered stacked state.

[0034] (Battery block 20) ​​Each battery block 20 houses multiple rechargeable battery cells 1. By combining and using multiple battery blocks 20, each housing multiple rechargeable battery cells 1, it is easy to adjust the number of rechargeable battery cells used. Furthermore, when using a large number of rechargeable battery cells, dividing them into multiple battery blocks improves the handling of each battery block and simplifies the configuration.

[0035] Each battery block 20 is composed of a battery holder 5 that houses multiple rechargeable battery cells 1. A circuit board 3 may also be added to the battery holder 5. In the examples shown in Figures 3 to 10 , multiple cylindrical rechargeable battery cells are housed and held vertically in the battery holder 5. The multiple rechargeable battery cells 1 are connected in series or parallel via lead plates 4 or the like. The number of series connections or parallel connections can be set as desired depending on the required specifications. In the examples shown in Figures 3 , 4 , and 10 , the first battery block 21 and the second battery block 22 each use 72 rechargeable battery cells 1, forming a 3 series × 24 parallel configuration, while the third battery block 23 uses 192 rechargeable battery cells 1, forming an 8 series × 24 parallel configuration. However, the present disclosure is not limited to this configuration, and any number of rechargeable battery cells can be used to achieve any series or parallel connection depending on the required specifications.

[0036] The battery holder 5 has multiple storage cylinders 6 that individually store the rechargeable battery cells 1. In the example shown in Figures 9 and 10, the battery holder 5 is divided into two sub-holders, each of which has a storage cylinder 6, and the two storage cylinders 6 sandwich and store the rechargeable battery cells 1. However, the present disclosure is not limited to this battery holder configuration; the battery holder may be divided into three or more sections, or one battery holder may have an opening at its end to allow the insertion of rechargeable battery cells. Such a battery holder 5 can be made of a resin such as polycarbonate, which has excellent insulating properties.

[0037] 9 and other figures, the battery holder 5 has a connection window 7 on the end surface of the cylindrical storage tube 6 so that the cell end surfaces 1a of the secondary battery cells 1 stored in the cylindrical storage tube 6 can be connected to the lead plates 4 from outside the battery holder 5. The connection window 7 is formed large enough to expose a portion of the cell end surfaces 1a.

[0038] As shown in Figure 2 and other figures, the battery block 20 is connected to a circuit board 3. The circuit board 3 is equipped with a charge / discharge circuit that charges and discharges the rechargeable battery cells 1, a protection circuit that monitors the voltage and temperature of the rechargeable battery cells 1 and cuts off the current in the event of an abnormality, and other components. The circuit board 3 is made of a glass epoxy board or other material. A board holder for holding the circuit board 3 may also be provided. The board holder can be connected to the battery holder 5. Furthermore, a junction box 8 carrying electrical components may be provided separately from the circuit board 3. In this case, the battery block 20 is connected to the junction box 8 and is connected to the circuit board 3 via the junction box 8. In the examples shown in Figures 2 to 5, the junction box 8 is located on the top surface of the first battery block 21. The junction box 8 contains protection circuit components such as a current fuse, relay, and pre-charging resistor.

[0039] (Lead Plates 4) The lead plates 4 connect the electrodes on the cell end faces 1a of the secondary battery cells 1 to each other, connecting multiple secondary battery cells 1 in series or parallel. In the example of Fig. 9, a lead plate 4 is disposed on each cell end face 1a of the secondary battery cells 1. Each cell end face 1a may also be divided into multiple lead plates 4. Each lead plate 4 is formed in a plate shape and connects the electrodes provided on the cell end faces 1a of the secondary battery cells 1 to each other.

[0040] These lead plates 4 are made of metal plates with excellent conductivity, such as aluminum or nickel. If necessary, a coating of nickel or other material may be added to the surface of the lead plate 4. The lead plate 4 is fixed to the cell end surface 1a of the secondary battery cell 1 by laser welding, spot welding, projection welding, or the like.

[0041] (Secondary battery cell 1) Each secondary battery cell 1 may be a secondary battery cell with a cylindrical or rectangular outer shape. In the examples shown in Figures 3, 4, 10, etc., cylindrical secondary battery cells 1 are arranged in a row in a vertical orientation with their axial directions aligned vertically. However, the number and arrangement of secondary battery cells 1 are not limited to this example, and any number and arrangement can be used as appropriate. For example, cylindrical secondary battery cells may be stacked in multiple stages. Furthermore, the stacked secondary battery cells may be arranged in a staggered pattern, or in a grid or matrix pattern.

[0042] The cylindrical secondary battery cell 1 has cell end faces 1a on both sides of the cylinder. The pair of cell end faces 1a is made up of a first cell end face 1a1 and a second cell end face 1a2.

[0043] Each secondary battery cell 1 has a positive and negative electrode, which are preferably provided on a first cell end surface 1a1 of the secondary battery cell 1. Such secondary battery cells 1 can be any known secondary battery, such as a lithium-ion secondary battery, a nickel-metal hydride battery, or a nickel-cadmium battery.

[0044] (Gas exhaust section 1c) The outer can of each secondary battery cell 1 is provided with a gas exhaust section 1c. The gas exhaust section 1c releases gas inside the outer can to the outside when the internal pressure of the outer can increases. The gas exhaust section 1c is provided on one of the cell end faces 1a of the secondary battery cell 1. In the example shown in FIG. 11 , the gas exhaust section 1c is provided on the first cell end face 1a1, which is the positive electrode side of the secondary battery cell 1. Such a gas exhaust section 1c can be configured as a gas exhaust valve that opens in response to an increase in internal pressure of the outer can. Alternatively, it may be a thin-walled section or a slit that breaks in response to an increase in internal pressure of the outer can.

[0045] The multiple secondary battery cells 1 are held in the storage tube 6 of the battery holder 5 and are arranged so that the cell end faces 1a are aligned on the same plane. A region where the first cell end faces 1a1 are aligned on the same plane is also provided collectively. This arrangement defines the region where high-temperature, high-pressure gas may be discharged from the secondary battery cells 1, and defines the placement region for the fireproof sheet 70, described below. Furthermore, concentrating the gas discharge region makes it easier to define a gas discharge path within the exterior case 10 that guides the gas to the case-side discharge hole 13.

[0046] On the other hand, the exterior case 10 has a case-side exhaust hole formed in a part thereof for releasing high-pressure gas to the outside when the gas exhaust portion 1c of the secondary battery cell 1 is opened and the gas is discharged. The case-side exhaust hole is formed, for example, in the first case 11 or the lid portion 14. The case-side exhaust hole may be rectangular, or may be a chamfered rectangle, a polygonal shape such as an octagon, hexagon, or square, or a circle, track, or ellipse.

[0047] (First battery block 21, second battery block 22, third battery block 23) Each battery block 20 has a pair of block main surfaces 24 and block end surfaces 25 that intersect with the pair of block main surfaces 24. Each block main surface 24 is formed in a rectangular shape. Furthermore, as shown in FIG. 6 , each battery block 20 has a block through-hole 26 that penetrates the pair of block main surfaces 24, with the end surface of the block through-hole 26 opening into each block main surface 24. In this manner, each block main surface 24 is disposed in a position that intersects with the connecting shaft 50. The first direction is a direction perpendicular to the connecting shaft 50. In the example of FIG. 6 , the first direction coincides with the extension direction of the rectangular shape of each block main surface 24 (the left-right direction in the figure).

[0048] In the example of Figure 5, the multiple battery blocks 20 are made up of three battery blocks 20, which are, from top to bottom, a first battery block 21, a second battery block 22, and a third battery block 23. The number of battery blocks 20 may be two or four or more. Even when there are two battery blocks, depending on the configuration, it may not be possible to ensure a heat conduction path with the outside. In such cases, a heat dissipation structure using a heat dissipation plate and heat dissipation tubes is effective.

[0049] The first battery block 21 is arranged so that the upper block main surface 24 of the second battery block 22 overlaps the lower block main surface 24. The block main surfaces 24 of the first battery block 21 and the second battery block 22 are approximately the same size and shape. On the other hand, the block main surface 24 of the third battery block 23 is formed larger than the block main surface 24 of the second battery block 22.

[0050] (Heat Dissipation Plate 30) As shown in Figures 5 to 10, a heat dissipation plate 30 is interposed at the interface between adjacent battery blocks 20 among the multiple battery blocks 20. Each heat dissipation plate 30 has a plate opening hole 32 at a position facing the end face of the block through-hole 26. Such heat dissipation plates 30 can be made of a material with excellent thermal conductivity, such as aluminum, copper, iron, or SUS. In the example of Figures 5 and 6, aluminum sheet metal is used.

[0051] 3 to 9, a heat dissipation plate 30 is also placed on the top surface of the first battery block 21, although not at the interface between the battery blocks. The junction box 8 is placed on the top surface of the first battery block 21 and is a heat source, so the presence of the heat dissipation plate 30 can improve heat dissipation at this interface as well.

[0052] (Heat Dissipation Tubes 40) As shown in Figures 3 to 11, a heat dissipation tube 40 is inserted into each block through-hole 26. Each heat dissipation tube 40 is pipe-shaped and has a tube through-hole 42 formed inside. The heat dissipation tubes 40 are preferably aligned in the same orientation as the cylindrical rechargeable battery cells 1. In this embodiment, the heat dissipation tubes 40 are inserted into the block through-holes 26 in the center of each battery block 20 using the storage cylinders 6 that do not house the rechargeable battery cells 1 of the battery holders 5 of each battery block 20, and are not covered by the lead plates 4. This allows the heat dissipation tubes 40 to be positioned unobtrusively within the battery block 20. Such heat dissipation tubes 40 can be made of a material with excellent thermal conductivity, such as aluminum, copper, iron, or stainless steel. The heat dissipation tubes 40 are preferably made of the same material as the heat dissipation plate 30.

[0053] (Connecting Shaft 50) The connecting shaft 50 is inserted into the tube through-holes 42 of the heat dissipation tubes 40. The connecting shaft 50 connects multiple battery blocks 20 stacked in multiple layers. Specifically, the heat dissipation tubes 40 are inserted into the block through-holes 26 of each battery block 20. In this state, as shown in Figures 3 to 11, the multiple battery blocks 20 are stacked in multiple layers with heat dissipation plates 30 interposed at the interfaces between adjacent battery blocks 20. At this time, the heat dissipation tubes 40 of each battery block 20 are coaxial with each other, and as shown in Figure 11, the heat dissipation tubes 40 are arranged coaxially on the front and back of each heat dissipation plate 30, i.e., the tube through-holes 42 of the heat dissipation tubes 40 arranged on the front and back are connected via the plate opening holes 32. In this state, connecting shafts 50 are inserted into the series of tube through-holes 42, and the ends of the connecting shafts 50 are fastened to the exterior case 10 to connect the multiple battery blocks 20. In this state, the connecting shafts 50 connect multiple battery blocks 20, while the heat dissipation tubes 40 and heat dissipation plates 30 are thermally coupled. This means that the battery blocks 20 are mechanically coupled and have a structure for heat dissipation at the same time. As a result, as shown in FIG. 12 , heat can be efficiently dissipated from the interior of the battery blocks 20 and the interfaces between the battery blocks 20, where heat tends to build up, via the thermally coupled heat dissipation tubes 40 and heat dissipation plates 30. The connecting shafts 50 are designed to be long enough to penetrate and connect multiple stacked battery blocks 20. A screw thread is formed at the tip of the connecting shaft 50. Furthermore, the connecting shaft 50 is made of a material with sufficient rigidity. In the examples shown in FIGS. 5 to 10 , stainless steel, molybdenum steel, steel, iron, etc. can be used.

[0054] In a battery pack composed of multiple secondary battery cells, if a large number of secondary battery cells are used, a core block may be formed by stacking multiple battery blocks connected to the secondary battery cells. In such a configuration, a structure that efficiently dissipates heat generated by each secondary battery cell is required. In this case, battery blocks located at the ends of the stacked battery blocks, such as the upper and lower tiers, are relatively easy to dissipate heat because they do not have battery blocks on one side. In contrast, battery blocks located in the middle are more likely to trap heat because they have battery blocks on both sides. This requires some kind of heat dissipation mechanism, but adding such a heat dissipation mechanism has raised concerns that the battery block will become larger, the configuration will become more complex, and costs will increase. On the other hand, a configuration in which battery blocks are stacked in multiple tiers also requires a certain level of connection strength between the battery blocks, so a fixing structure is also necessary.

[0055] Therefore, in the battery pack 100 according to this embodiment, heat dissipation tubes 40 are disposed within each battery block 20, and heat dissipation plates 30 are disposed at the interfaces of the battery blocks 20. The heat dissipation tubes 40 and the heat dissipation plates 30 are thermally coupled by long connecting shafts 50. This realizes a heat dissipation structure that efficiently conducts heat from within the battery blocks 20 and dissipates it. A fastening structure is also realized in which the connecting shafts 50 penetrate the stacked battery blocks 20 in the stacking direction. In this way, the heat dissipation structure and fastening structure can be realized with a common structure using the heat dissipation plates 30, heat dissipation tubes 40, and connecting shafts 50. Furthermore, the thin heat dissipation plates 30 prevent the battery pack 100 from becoming too tall. Furthermore, by arranging the heat dissipation tubes 40 in the same orientation as the secondary battery cells 1, the heat dissipation tubes 40 can be added to the battery blocks 20 without interfering with their placement, thereby preventing the battery pack 100 from becoming too large. In addition, by forming the second case 12 from a material with high thermal conductivity and thermally coupling it to the heat dissipation structure, the heat dissipation performance can be further improved.

[0056] Each battery block 20 can have heat dissipation tubes 40 embedded in multiple different locations. The block main surface 24 is formed in a chamfered rectangular or trapezoidal shape extending in a first direction, perpendicular to the connecting shaft 50. The first direction is one direction perpendicular to the connecting shaft 50. When each battery block 20 has a chamfered rectangular shape as in the embodiment, the first direction is preferably the longitudinal direction of the block main surface 24. In the example shown in Figures 5 to 8, the first battery block 21 and the second battery block 22 have different widths in the first and second directions that are perpendicular to the connecting shaft 50 and perpendicular to each other, and the width in the horizontal first direction is longer than the width in the vertical second direction in the figures. In these first battery blocks 21 and second battery blocks 22, the block through-holes 26 through which the heat dissipation tubes 40 are disposed are spaced apart in the first direction. By arranging the plurality of heat dissipation tubes 40 at intervals in the longitudinal direction in this manner, even an elongated battery block 20 can dissipate heat from each of the heat dissipation tubes 40 arranged along the longitudinal direction, thereby achieving nearly uniform cooling capacity.

[0057] The block through-holes 26 may also be spaced apart in a second direction intersecting the first direction. In the examples of Figures 5 to 8, multiple block through-holes 26 are also spaced apart in the short direction of the first battery block 21 and the second battery block 22. Here, the block through-holes 26 are provided on the back side of the battery block 20 in the figures. In this way, forming block through-holes 26 in the parts of each battery block 20 that face the outside allows for efficient cooling from the surface of the battery block 20.

[0058] The third battery block 23 houses more rechargeable battery cells 1 than the first battery block 21 or the second battery block 22, and has the same width as the first battery block 21 or the second battery block 22, resulting in a shape that protrudes forward. That is, unlike the first battery block 21 or the second battery block 22, the third battery block 23 has a first direction that is the short side (left-right direction in FIG. 5 , etc.) and a second direction that is the long side (front-rear direction in FIG. 5 , etc.). However, because the first battery block 21 or the second battery block 22 is not present on the upper surface of the forward-protruding region, heat dissipation is also achieved from the upper surface of the third battery block 23. Furthermore, as shown in FIG. 3 , FIG. 5 , etc., the heat dissipation plate 30 disposed at the interface between the second battery block 22 and the third battery block 23 extends its front surface to cover the upper surface of the third battery block 23, including the region where the second battery block 22 is not present, thereby enhancing heat dissipation from the upper surface. 2 and 3, the lower half of the third battery block 23 is housed in the second case 12, and by making the second case 12 out of metal, heat dissipation from the underside is also promoted. Therefore, in the third battery block 23, block through-holes 26 are provided only in the rear area where the first battery block 21 and second battery block 22 are stacked, and additional heat dissipation is promoted by the heat dissipation structure using the heat dissipation plate 30 and heat dissipation tubes 40.

[0059] Additionally, by thermally coupling at least a portion of the outer case 10 to the core block 2 using metal, heat dissipation can be further enhanced. Specifically, the second case 12 constituting the outer case 10 is made of metal and is fastened to the connecting shaft 50 while being thermally coupled to the heat dissipation tube 40 that is exposed at the end of the block through-hole 26 on the block main surface 24, which forms the bottom surface of the core block 2. This allows the connecting shaft 50 to be fastened to the second case 12, which has excellent thermal conductivity, and heat can be conducted to the second case 12 via the heat dissipation tube 40, further enhancing heat dissipation. For this reason, the second case 12 is formed with a screw boss 16 for fastening the tip of the connecting shaft 50. As shown in FIG. 12 , the end surface of the screw boss 16 around the threaded hole abuts against the open end of the heat dissipation tube 40 that surrounds the tip of the connecting shaft 50 on the bottom surface of the core block 2. As a result, by fastening the connecting shaft 50 to the screw boss 16, the open end of the heat dissipation tube 40 and the end face of the screw boss 16 are thermally coupled, forming a heat dissipation path HP from the heat dissipation tube 40 to the second case 12.

[0060] (Heat Dissipation Sheet 60) The core block 2 may also include a heat dissipation sheet 60. The heat dissipation sheet 60 is disposed at the interface between the heat dissipation plate 30 and the block main surface 24 of the battery block 20. The heat dissipation sheet 60 is composed of a material with high thermal conductivity. The heat dissipation sheet 60 is preferably flexible. As shown in Figures 6, 7, 8, 9, 10, and 11, the flexible heat dissipation sheet 60 can be interposed at the interface between the heat dissipation plate 30 and the battery block 20 to prevent gaps from forming at the interface, thereby enhancing thermal bonding and improving thermal conductivity. In particular, when the heat dissipation plate and battery holder, both of which are hard materials, are directly stacked, gaps are likely to form at the interface, creating an air gap that creates an insulating effect and reduces thermal conductivity. Therefore, by interposing a flexible heat dissipation sheet 60 at the interface between the hard materials, the formation of such an air gap can be avoided and thermal bonding can be improved.

[0061] The heat dissipation sheet 60 is also preferably insulating, which can prevent unintended electrical conduction to conductive members such as the lead plates 4. In other words, the heat dissipation sheet 60 can also serve to insulate the interface between the heat dissipation plate 30, which is made of metal or other conductive material, and the battery block 20. Such a heat dissipation sheet 60 can be made of silicone resin, polyimide resin, acrylic resin, or the like, which contains a highly thermally conductive filler.

[0062] (Fireproof Sheet 70) The core block 2 may also be equipped with a fireproof sheet 70. The fireproof sheet 70 is preferably positioned at the interface between the heat dissipation plate 30 and the block main surface 24 of the battery block 20 so as not to overlap with the heat dissipation sheet 60. This allows the fireproof sheet 70 to prevent the flame from reaching the opposing battery block 20 across the heat dissipation plate 30, thereby enhancing safety. Such a fireproof sheet 70 is made of a material such as silica or mica.

[0063] The fireproof sheet 70 is provided only in the area of ​​each of the multiple secondary battery cells 1 that faces the first cell end face 1a1, where the gas exhaust port is provided. That is, between the heat dissipation plate 30 and the block main surface 24 of the battery block 20, the fireproof sheet 70 is provided in the area that faces the first cell end face 1a1, and the heat dissipation sheet 60 is provided in the area that faces the second cell end face 1a2, as shown in Figure 11. The fireproof sheet 70 has low thermal conductivity to provide heat resistance, while the heat dissipation sheet 60 has high thermal conductivity. Therefore, by arranging these sheets with opposing properties separately, the functions of each sheet can be effectively utilized.

[0064] Furthermore, these fireproof sheets 70 and heat dissipation sheets 60 are preferably placed on both sides of the heat dissipation plate 30. This makes it possible to improve the heat dissipation properties of the battery block 20 and safety during gas release on the top and bottom surfaces of the heat dissipation plate 30.

[0065] Furthermore, the heat dissipation sheet 60 and the fire-resistant sheet 70 have openings or bypasses in the areas where the heat dissipation tubes 40 are located. By bypassing, we mean a configuration in which the heat dissipation sheet 60 or the fire-resistant sheet 70 is not interposed at the interface between the heat dissipation tubes 40 and the heat dissipation plate 30, such as by partially cutting out or recessing the end shape. This prevents the heat dissipation sheet 60 or the fire-resistant sheet 70 from interfering with the thermal bonding at the interface between the heat dissipation tubes 40 and the heat dissipation plate 30.

[0066] 11, a step 44 is preferably formed on the end face of the heat dissipation tube 40. This prevents the heat dissipation sheet 60 or the fireproof sheet 70 from interfering with the thermal bonding at the joint interface between the heat dissipation tube 40 and the heat dissipation plate 30. The portion where the heat dissipation sheet 60 or the fireproof sheet 70 is to be placed may be configured to be fixed and positioned by being sandwiched between the step 44 of the heat dissipation tube 40.

[0067] (Bus bars 80) Furthermore, the lead plates 4 arranged on the block main surfaces 24 are connected to other lead plates 4 via bus bars 80. In a configuration in which a heat dissipation plate 30 is interposed between battery blocks 20, the heat dissipation plate 30 inhibits electrical connection between the battery blocks 20. To electrically connect the battery blocks 20 beyond the heat dissipation plate 30, it is possible to partially drill holes in the heat dissipation plate 30 and electrically connect the lead plates 4 through these holes. However, this poses a problem of reduced heat dissipation in the holed areas because the heat dissipation plate 30 is not present in these areas. Therefore, in the battery pack 100 according to this embodiment, the bus bars 80 connecting the lead plates 4 to each other are arranged on the outer edges of the heat dissipation plate 30, thereby achieving electrical connection between the battery blocks 20 while the heat dissipation plate 30 is positioned at the interface where the battery blocks 20 are stacked.

[0068] FIG. 13 shows how the battery blocks 20 are electrically connected around the heat dissipation plate 30 via the bus bar 80. This figure shows how the lead plate 4A of the first battery block 21 is connected to the lead plate 4 of the second battery block 22. For ease of explanation, the first battery block 21 is not shown, and only the lead plate 4A connected to the first battery block 21 is shown. The lead plate 4A has a lead screw hole 4A1 for connection to the bus bar 80. The bus bar 80 is formed by bending a rectangular metal plate. First and second connection holes 81 and 82 are formed at both ends of the bus bar 80 to connect the lead plate 4A of the first battery block 21 to the lead plate 4 of the second battery block 22, respectively. Furthermore, the bus bar 80 is bent at two points to create an inclined surface in the middle and to make the heights of both ends different, so that the lead plate 4A of the first battery block 21 and the lead plate 4 of the second battery block 22, which are at different heights, can be connected. This bus bar 80 is screwed together by aligning the first connection hole 81 with the lead screw hole 4A1 of the lead plate 4A of the first battery block 21, and the second connection hole 82 with the lead screw hole 4A1 of the lead plate 4 of the second battery block 22. The screw boss 16 of the battery holder 5 of the first battery block 21 is also placed below the first connection hole 81 of the lead plate 4. In this case, the first battery block 21 and the second battery block 22 can also be screwed together with a common screw by also placing the screw boss 16 of the battery holder 5 of the second battery block 22 below the screw boss 16 of the first battery block 21.

[0069] 13 , plate notches 34 are formed on the edge of the heat dissipation plate 30. Bus bars 80 are placed in these plate notches 34. This makes it easier to position and place the bus bars 80 on the edge of the lead plates 4. In particular, by forming plate notches 34 in the corners of the heat dissipation plate 30, the screws that connect the lead plates 4 and bus bars 80 can be used in common with the components that connect the battery blocks 20, making it possible to simultaneously physically join and electrically connect the battery blocks 20.

[0070] (Current Collector Plate 90) The battery block 20 may further include a metal current collector plate 90 thicker than the lead plate 4 that is layered on the lead plate 4. Thinner lead plates 4 result in higher electrical resistance and greater heat generation. The greater the current flow, the greater the heat generation. On the other hand, thicker lead plates 4 result in poorer workability. Therefore, by laminating a metal current collector plate 90 thicker than the lead plate 4 separately from the lead plate 4, electrical resistance can be reduced, enabling a configuration that can withstand large currents. Furthermore, increasing the thickness of the lead plate 4 by laminating such current collector plates 90 provides effective strength for fastening to the bus bar 80 by screwing or other means. The example in Figure 13 shows a state in which a current collector plate 90 is layered on each of the lead plate 4A of the first battery block 21 and the lead plate 4 of the second battery block 22. In Figure 13, a current collector plate 90 is layered on the back side of the lead plate 4A of the first battery block 21 and on the front side of the lead plate 4 of the second battery block 22.

[0071] In the above example, the battery pack is used as a power source for an electric scooter. However, the present disclosure is not limited to this. The battery pack can also be used for other purposes, such as attaching it to an electric device to be driven and supplying power to the electric device. Examples of electric devices include mobile objects such as electric vehicles and electric carts, as well as portable electric devices. In such electric devices, when the remaining capacity of the battery pack becomes low or the battery pack deteriorates over time, the battery pack can be replaced to continue using the electric device. However, the present disclosure is not limited to replaceable battery packs that mainly house secondary battery cells, but can also be applied to battery packs in which secondary battery cells are housed within the housing of the electric device. In the present disclosure, a battery pack is defined as a battery pack that houses secondary battery cells in a case, and also includes battery packs in which secondary battery cells for driving the electric device are built into the housing of the electric device itself. In other words, the present disclosure is not limited to replaceable battery packs, but can also be applied to electric devices that house secondary battery cells.

[0072] The battery pack according to the present invention can be suitably used as a driving power source for mobile objects such as electric scooters, electric carts and assisted bicycles, as a power source for radios, and as a power source for portable electrical equipment such as electric cleaners and power tools, as a backup power source for servers and the like, and as a stationary power storage device for home, office and factory use, etc.

[0073] DESCRIPTION OF SYMBOLS 100...Battery pack 1...Secondary battery cell 1a...Cell end face 1a1...First cell end face 1a2...Second cell end face 1c...Gas exhaust section 2...Core block 3...Circuit board 4...Lead plate 4A...Lead plate of first battery block 21 4A1...Lead screw hole 5...Battery holder 6...Storage tube 7...Connection window 8...Junction box 10...External case 11...First case 12...Second case 14...Cover portion 16...Screw boss 20...Battery block 21...First battery block 22...Second battery block 23...Third battery block 24...Block main surface 25...Block end face 26...Block through hole 30...Heat dissipation plate 32...Plate opening hole 40...Heat dissipation tube 42...Tube through hole 44...Step 50...Connecting shaft 60...Heat dissipation sheet 70...Fireproof sheet 80...Bus bar 81...First connection hole 82...Second connection hole 90...Current collecting plate HP...Heat dissipation path

Claims

1. A battery pack comprising: a plurality of battery blocks each including a plurality of secondary battery cells, each having a pair of block main surfaces and block end surfaces intersecting the pair of block main surfaces, with end faces of block through holes penetrating the pair of block main surfaces opening into each of the pair of block main surfaces; heat dissipation plates arranged between adjacent battery blocks among the plurality of battery blocks, between the block main surface of the pair of block main surfaces that faces the adjacent battery block, with plate opening holes opened at positions facing the end faces of the block through holes; heat dissipation tubes having tube through openings therein that are inserted into the block through holes; and connecting shafts that are inserted into the tube through openings of the adjacent battery blocks, with the heat dissipation tubes coaxially arranged on the front and back of the heat dissipation plate so that the tube through openings on the front and back are connected via the plate opening holes, and that connect the adjacent battery blocks via the heat dissipation tubes of the adjacent battery blocks so that the heat dissipation tubes and the heat dissipation plate are thermally coupled to each other.

2. A battery pack as claimed in claim 1, wherein the plurality of battery blocks are arranged with the pair of block main surfaces perpendicular to the connecting shaft, and the block through-hole is one of a plurality of block through-holes that open in the pair of block main surfaces and are spaced apart in a direction perpendicular to the connecting shaft.

3. A battery pack according to claim 1, wherein the plurality of battery blocks have the block through-hole as one of a plurality of block through-holes that are opened along the edges of the pair of block main surfaces and are spaced apart from each other.

4. A battery pack according to claim 1, wherein the heat dissipation plate and the heat dissipation tube are each made of metal.

5. A battery pack as claimed in claim 1, further comprising a thermally conductive outer case that houses a core block formed by joining the plurality of battery blocks, wherein the outer case is fastened to the connecting shaft while being in thermally coupled contact with a heat dissipation tube that is exposed at the end face of the block through-hole on one of the pair of block main faces that constitute one face of the core block.

6. A battery pack as claimed in claim 5, wherein the exterior case is divided into a first case and a second case, and the second case is provided with a screw boss that abuts against the tip of the connecting shaft and the open end of the heat dissipation tube that surrounds the tip of the connecting shaft.

7. A battery pack according to claim 6, wherein the second case is made of metal.

8. A battery pack as claimed in claim 1, wherein the plurality of battery blocks include a first battery block, a second battery block arranged on the block main surface of the first battery block, and a third battery block arranged on the block main surface of the second battery block, and the block main surface of the third battery block is larger than the block main surface of the second battery block.

9. A battery pack according to any one of claims 1 to 8, further comprising an insulating and flexible heat dissipation sheet disposed at the interface between the heat dissipation plate and the main surface of the battery block.

10. A battery pack as claimed in claim 9, further comprising a fire-resistant sheet arranged at the interface between the heat dissipation plate and the main surface of the battery block in a position that does not overlap the heat dissipation sheet in a plan view.

11. A battery pack as claimed in claim 10, wherein each of the plurality of secondary battery cells is provided with a gas exhaust section on one of a pair of cell end faces for exhausting gas when the internal pressure rises, and the fireproof sheet is positioned opposite one of the cell end faces.

12. A battery pack as claimed in claim 10, wherein the end face of the heat dissipation tube is provided with a step, and the heat dissipation sheet and the fireproof sheet each have an opening or a bypass around the location where the heat dissipation tube is placed.

13. A battery pack according to any one of claims 1 to 8, further comprising: lead plates arranged on each of the pair of block main surfaces and connecting the plurality of secondary battery cells; and bus bars connected to the lead plates at the outer edge of the heat dissipation plate.

14. A battery pack according to claim 13, wherein the heat dissipation plate has plate notches at its edge, and the bus bars are arranged in the plate notches.

15. A battery pack according to claim 13, further comprising a metal current collector plate that is laminated with the lead plate and is thicker than the lead plate, and the bus bar is connected to the current collector plate.

16. A battery pack according to any one of claims 1 to 8, wherein the heat dissipation tubes are arranged parallel to the axes of the plurality of secondary battery cells.

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