Battery pack and electric vehicle equipped with the battery pack

Abstract

The present invention relates to a battery pack and an electric vehicle equipped with the battery pack. The battery pack can include at least one battery cell, a case that accommodates the at least one battery cell and has a bottom wall facing downward from the at least one battery cell, and a protection panel that is joined to a lower surface of the bottom wall of the case with an adhesive. A weld bead caused by friction stir welding and a hole located at one end of the weld bead can exist on the lower surface of the bottom wall of the case, and the hole can be covered with the adhesive.

Description

Technical Field

[0001] This disclosure relates to a battery pack and an electric vehicle equipped with the battery pack. Background Technology

[0002] Japanese Unexamined Patent Application Publication No. 2024-147845 (JP 2024-147845 A) describes a battery pack housing. In this housing, multiple constituent components are joined together by friction stir welding. In friction stir welding, a tool with a protrusion (also called a probe) at its tip is rotated while pressing against the components to be joined, causing the protrusion to penetrate into the components. Around the tool, the components to be joined are softened by frictional heat and mixed together while undergoing plastic flow due to the rotation of the tool. Therefore, the components to be joined are integrally formed. Summary of the Invention

[0003] In friction stir welding, characteristic weld beads remain on the product, and tool exit holes inevitably form at one end of the weld bead. For this reason, if the battery pack housing is friction stir welded, the tool exit holes formed on the housing surface may adversely affect the housing's sealing performance. It is conceivable to cover the surface with the tool exit holes with a protective panel; however, a protective panel alone is insufficient to reliably prevent the ingress of water and foreign matter.

[0004] This disclosure provides a technique for improving the sealing performance of housings manufactured by friction stir welding.

[0005] The present disclosure provides a battery pack. The battery pack may include at least one battery cell, a housing containing the at least one battery cell and having a bottom wall facing the at least one battery cell from below, and a protective panel bonded to the lower surface of the bottom wall of the housing using an adhesive. Weld beads resulting from friction stir welding and a hole located at one end of the weld bead (i.e., a tool withdrawal hole) may exist on the lower surface of the bottom wall of the housing, and the hole may be covered with an adhesive.

[0006] With the above configuration, the pores caused by friction stir welding are covered with adhesive, thereby avoiding or suppressing the reduction in sealing performance at the pores. By using adhesive to bond the protective panel, the sealing performance of the housing manufactured by friction stir welding can be improved without using new parts or processes.

[0007] The present disclosure also provides an electric vehicle that travels on a road surface. The electric vehicle includes a body and a battery pack supported by the body. The battery pack can be any of the battery packs disclosed herein. In this case, the protective panel of the battery pack can be exposed to the road surface. Due to the significantly improved sealing performance of the housing, all battery packs of the present disclosure can be effectively used as a power source for the electric vehicle. Attached Figure Description

[0008] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same symbols denote the same elements, and wherein: Figure 1 It is a diagram schematically illustrating the configuration of an electric vehicle; Figure 2 The battery pack configuration is shown; Figure 3 The battery module is shown when viewed from below; Figure 4 It is along Figure 2 A cross-sectional view taken from line IV-IV in the diagram; Figure 5 yes Figure 4 A magnified view of part of V in the image; Figure 6 This is a view of the casing as seen from below; and Figure 7 The view shown below shows the battery pack with the protective panel attached. Detailed Implementation

[0009] In one embodiment of the technology, at least a portion of the hole may be filled with adhesive. This configuration allows for more reliable prevention or suppression of reduced sealing performance at the hole.

[0010] In one embodiment of this technology, the bottom wall of the housing may include an upper panel and a lower panel facing each other. In this case, a channel for the flow of heat transfer medium can be defined between the upper and lower panels. With this configuration, there is a concern that holes caused by friction stir welding may reduce the sealing performance of the channel. However, since the holes are covered with adhesive, this concern can be eliminated or reduced.

[0011] In one embodiment of this technology, the upper and lower panels can be joined to each other at weld seams. With this configuration, weld seams and / or holes resulting from friction stir welding reach the upper panel, thus raising concerns about reduced sealing performance at the holes. However, since the holes are covered with adhesive, this concern can be eliminated or reduced.

[0012] In one embodiment of this technology, the housing may further include a beam fixed to the upper surface of the bottom wall. In this case, a hole formed in the lower surface of the bottom wall may be located directly below the beam. With this configuration, while the hole is sealed with adhesive, the protective panel can be adhesively bonded to the beam-reinforced portion of the bottom wall of the housing.

[0013] In one embodiment of this technology, the beam of the housing may extend along the upper surface of the bottom wall. In this case, at least a portion of the weld bead may be located directly below the beam and may extend along the lower surface of the bottom wall in the same direction as the beam. In friction stir welding, unintended cavities can form not only at tool exit holes but also in other portions of the weld bead. In this case, if the beam is located directly above the weld bead, the reduction in the sealing performance of the housing due to the cavity can be avoided or suppressed by the beam.

[0014] In the above embodiment, the beams of the housing can be joined to the bottom wall at weld points. In other words, the weld can extend from the bottom wall of the housing to the beams. By employing this technique, friction stir welding can be actively used to join various components constituting the housing.

[0015] In one embodiment of this technology, the upper surface of the protective panel may have a main region and a protruding region projecting upward from the main region. In this case, the main region may face the lower surface of the bottom wall of the housing via a gap. Alternatively, the protruding region may be bonded to the lower surface of the bottom wall of the housing using an adhesive. With this configuration, when a gap is formed between the protective panel and the housing, the transmission of external forces applied to the protective panel to the housing can be avoided or suppressed.

[0016] In the above embodiments, the housing may further include a beam fixed to the upper surface of the bottom wall. In this case, the hole formed in the lower surface of the bottom wall may be located directly below the beam and directly above the protruding area of ​​the upper surface of the protective panel. With this configuration, in addition to the aforementioned advantages, the protective panel can be bonded to the beam-reinforced portion of the bottom wall of the housing using adhesive while the hole can be sealed with adhesive.

[0017] In one embodiment of this technology, the bottom wall of the housing can be made of metal, and the protective panel can be made of resin. Because the protective panel made of resin is relatively lightweight, it can be bonded with sufficient strength even when using adhesives.

[0018] A battery pack 20 according to an embodiment will be described with reference to the accompanying drawings. The battery pack 20 of this embodiment can be installed on an electric vehicle 10. Reference will be made to... Figure 1Electric vehicle 10 is described. Electric vehicle 10 is a battery electric vehicle (BEV). However, electric vehicle 10 is not limited to BEV, and can also be another type of electric vehicle, such as a hybrid electric vehicle (HEV) and a plug-in hybrid electric vehicle (PHEV).

[0019] Here, the orientation of the battery pack 20 in the specification and accompanying drawings refers to the orientation of the battery pack 20 when it is installed on the electric vehicle 10, and corresponds to the orientation within the electric vehicle 10. In the accompanying drawings, direction FR indicates the front side in the front-rear direction of the electric vehicle 10, and the negative direction RR of direction FR indicates the rear side in the front-rear direction of the electric vehicle 10. Direction LH indicates the left-hand side in the left-right direction of the electric vehicle 10, and the negative direction RH of direction LH indicates the right-hand side in the left-right direction of the vehicle. Direction UP indicates the upper side in the vertical direction of the electric vehicle 10, and the negative direction DW of direction UP indicates the lower side in the vertical direction of the electric vehicle 10.

[0020] The electric vehicle 10 includes a battery pack 20, a body 12, multiple wheels 14 and 16, and a motor unit 18. The electric vehicle 10 is an electric vehicle. The body 12 is formed of metal, such as steel-based materials and aluminum-based materials. The wheels 14 and 16 support the body 12. The wheels 14 and 16 include a pair of front wheels 14 located at the front of the body 12 and a pair of rear wheels 16 located at the rear of the body 12. The front wheels 14 are located on the right and left sides of the body 12, respectively. The rear wheels 16 are located on the right and left sides of the body 12. The body 12 has an interior compartment 12c. The compartment 12c is configured to accommodate occupants. The body 12 has a floor panel 12p. The floor panel 12p defines the floor of the compartment 12c.

[0021] Motor unit 18 includes a drive motor for driving front wheel 14. However, motor unit 18 is not limited to driving front wheel 14, and can be configured to drive at least one of wheels 14, 16. Motor unit 18 can be located at the front of carriage 12c.

[0022] The battery pack 20 is electrically connected to the motor unit 18 via, for example, a power converter (not shown). The battery pack 20 supplies power to the motor unit 18 for driving the wheels 14, 16. The battery pack 20 is located at the lower part of the vehicle body 12. Specifically, the battery pack 20 is located below the floor panel 12p of the vehicle body 12. The battery pack 20 is supported by the vehicle body 12. For example, the battery pack 20 can be fixed to the right side beam and the left side beam of the vehicle body 12.

[0023] Reference Figures 2 to 7 Describe the details of battery pack 20. For example... Figure 2As shown, the battery pack 20 is a thin battery pack with a smaller dimension in the vertical direction. The battery pack 20 has a flat cuboid shape. The dimension of the battery pack 20 in the vertical direction is smaller than the dimension of the battery pack 20 in the horizontal direction, and the dimension of the battery pack 20 in the horizontal direction is smaller than the dimension of the battery pack 20 in the front-back direction.

[0024] The battery pack 20 includes multiple battery modules 50, a housing 22, a protective panel 38, and a cover 44. The housing 22 houses the battery modules 50.

[0025] like Figure 3 As shown, each battery module in battery module 50 includes multiple battery cells 52. In a variation, battery module 50 may include only one battery cell 52. Each of the battery cells 52 is a rechargeable and dischargeable secondary battery cell. The secondary battery cell is, for example, a lithium-ion battery cell. Battery module 50 has an opening 51 in its lower surface 50b. At the lower surface 50b of battery module 50, the end face of each battery cell 52 is exposed through the opening 51. Each battery cell 52 is a pouch cell (also called a laminated cell). Each of the battery cells 52 has a flat shape. The battery cell 52 is oriented along its thickness direction ( Figure 3 The battery cells 52 are stacked in the left-right direction. The individual battery cells 52 are constrained by the fixing straps 54 while compressed along the stacking direction. The battery module 50 is stacked in a direction perpendicular to the stacking direction of the individual battery cells 52. Figure 3 The battery module 50 has a positive terminal 60a and a negative terminal 60b on one end side (in the front-to-back direction). The battery module 50 has a module housing 56 that houses the battery cells 52. An opening 51 is defined by the module housing 56.

[0026] The casing 22 is made of a metal such as aluminum. Figure 2 and Figure 4 As shown, the housing 22 includes a housing body 24 and a plurality of beams 34a, 34b, 34c, 36. The housing body 24 has a bottom wall 26 and a peripheral wall 32. The battery module 50 is disposed on the bottom wall 26. The peripheral wall 32 is upright from the outer peripheral edge 26e of the bottom wall 26. The peripheral wall 32 extends around the outer peripheral edge 26e of the bottom wall 26 for a complete circle. The housing body 24 has an upwardly opening 25. The opening 25 is defined by the inner surface of the peripheral wall 32. The cover 44 is a plate-like member configured to close the opening 25 of the housing body 24 from above. The cover 44 is made of a metal such as aluminum.

[0027] Beams 34a, 34b, 34c, and 36 are frame members of the shell 22. Beams 34a, 34b, 34c, and 36 extend along the upper surface 26a of the bottom wall 26. Beams 34a, 34b, 34c, and 36 comprise a plurality of first beams 34a, 34b, and 34c and a second beam 36. Each of the first beams 34a, 34b, and 34c extends in a left-right direction to cross the upper surface 26a of the bottom wall 26. Each of the first beams 34a, 34b, and 34c extends from the left peripheral wall 32 to the right peripheral wall 32. The second beam 36 extends in a front-rear direction to cross the upper surface 26a of the bottom wall 26 longitudinally. The first beams 34a, 34b, and 34c are spaced apart from each other in the front-rear direction. The second beam 36 is positioned at the center of the bottom wall 26 in a left-right direction. Each of the first beams 34a, 34b, and 34c (hereinafter referred to as first beam 34) is orthogonal to the second beam 36. Figure 4 As shown, each extension of the first beam 34 crosses the second beam 36. The first beam 34 and the second beam 36 are configured to engage with each other. The beams 34 and 36 are fixed to the upper surface 26a of the bottom wall 26.

[0028] The bottom wall 26 includes an upper panel 28 and a lower panel 30 facing each other in the vertical direction. Each of the upper panel 28 and the lower panel 30 is a plate-like member. The upper panel 28 and the lower panel 30 are joined together. A channel 40 for the flow of a heat transfer medium is defined between the upper panel 28 and the lower panel 30. The bottom wall 26 of the housing 22 serves as a cooler for the battery module 50. In this example, the lower panel 30 has a corrugated shape to form the channel 40. As a result, the upper surface 30a of the lower panel 30 has a contact area 30c that contacts the lower surface 28 of the upper panel 28 and a recessed area 30d that is recessed downward from the contact area 30c. The channel 40 is formed between the lower surface 28b of the upper panel 28 and the recessed area 30d of the lower panel 30. The temperature of the battery module 50 disposed on the upper surface 26a of the bottom wall 26 is regulated by the flow of the heat transfer medium through the channel 40. In this example, the heat transfer medium may be a coolant.

[0029] Figure 6 This is a view of the housing 22 as seen from below. Figure 6 In the middle, the channel 40 formed inside the bottom wall 26 is indicated by a single-point long dashed line. Figure 6 In the diagram, beams 34 and 36, fixed to the upper surface 26a of the bottom wall 26, are represented by dashed lines. For example... Figure 6 As shown, a supply port 40a through which the heat transfer medium is supplied to the channel 40 and a discharge port 40b through which the heat transfer medium is discharged from the channel 40 are located at the front end 26f of the bottom wall 26. The channel 40 extends from the supply port 40a to the discharge port 40b in a tortuous manner.

[0030] Friction stir welding is employed to join the upper panel 28 and lower panel 30 of the bottom wall 26. Multiple weld beads WJ formed by friction stir welding are formed on the lower surface 26b of the bottom wall 26. Figure 6 In the diagram, weld beads WJ are indicated by shaded lines. Each weld bead WJ extends along the lower surface 26b of the bottom wall 26. Each weld bead WJ is located directly below either of the beams 34 or 36. Each weld bead WJ extends in the direction of extension of the corresponding beam in the beams 34 or 36 (i.e., left-right or front-back). A hole 26h, caused by friction stir welding, is formed at one end of each weld bead WJ in the direction of extension. In other words, the hole 26h is formed in the final stage of friction stir welding when the tool is withdrawn.

[0031] like Figure 4 and Figure 5 As shown, each hole in hole 26h passes through the lower panel 30 and the upper panel 28 and reaches a corresponding beam in beams 34 and 36 (in Figure 2 as well as Figure 5 The first beam 34 in the middle). The cross-section of the weld bead WJ has an upwardly projecting dome shape. This cross-section is taken perpendicular to the direction in which the weld bead WJ extends. Each of the weld beads WJ is formed such that the cross-sectional area increases from the top surface 26h1 of the hole 26h toward the lower surface 26b of the bottom wall 26. As in the case of the hole 26h, each of the weld beads WJ extends from the lower panel 30 to a corresponding one of the beams 34, 36. In other words, the upper panel 28 and the lower panel 30 are joined to each other at the weld bead WJ. The beams 34, 36 are joined to the bottom wall 26 at the weld bead WJ.

[0032] A protective panel 38 is disposed on the lower surface 26b of the bottom wall 26. The protective panel 38 is a plate-like member with a predetermined profile. The protective panel 38 is a protective member and covers the bottom wall 26 from below. The protective panel 38 is located at the bottommost part of the battery pack 20 and is exposed to the road surface. By providing the protective panel 38, the impact of the road surface and other factors (such as impacts and rain) on the battery module 50 is reduced. The protective panel 38 is bonded to the lower surface 26b of the bottom wall 26 using an adhesive 42. The protective panel 38 is made of resin. Therefore, because the protective panel 38 is relatively lightweight, it can be bonded with sufficient strength even using the adhesive 42.

[0033] Some of the adhesive in the adhesive 42 binds the protective panel 38 to the bottom wall 26 and covers the hole 26h on the lower surface 26b of the bottom wall 26. In this example, the adhesive 42 also fills the interior of the hole 26h. In other words, the hole 26h is sealed by the adhesive 42.

[0034] As described above, in this embodiment, friction stir welding is used to join the upper panel 28 and the lower panel 30. When the panels 28 and 30 constituting the bottom wall 26 are joined by friction stir welding in this manner, a characteristic weld bead WJ remains on the bottom wall 26, and a hole 26h is inevitably formed at one end of the weld bead WJ. In particular, the hole 26h formed during friction stir welding as a tool withdrawal hole may adversely affect the sealing performance of the housing 22.

[0035] In this embodiment, the hole 26h on the lower surface 26b of the bottom wall 26, created by friction stir welding, is covered with adhesive 42. As a result, a decrease in sealing performance at the hole 26h is avoided or suppressed. By using adhesive 42 to bond the protective panel 38 to the bottom wall 26, the sealing performance of the housing 22 manufactured by friction stir welding can be improved without using new components or processes.

[0036] Specifically, in this embodiment, each of the holes 26h in the bottom wall 26 is completely filled with adhesive 42. This configuration allows for more reliable prevention or suppression of any reduction in the sealing performance of the housing 22 at the holes 26h. In a variation, each of the holes 26h does not need to be completely filled with adhesive 42. It is sufficient for each of the holes 26h to be at least partially filled with adhesive 42. While not limited to this, the holes 26h in the bottom wall 26 facing areas other than the area where the protective panel 38 is joined can also be similarly covered with adhesive 42.

[0037] In this embodiment, the bottom wall 26 of the housing 22 includes an upper panel 28 and a lower panel 30 facing each other, and a channel 40 for the flow of the heat transfer medium is defined between the two panels 28 and 30. With this configuration, there is a concern that the holes 26h caused by friction stir welding may reduce the sealing performance of the channel 40. However, since the holes 26h are covered with adhesive 42, this concern can be eliminated or reduced.

[0038] In this embodiment, the two panels 28, 30 constituting the bottom wall 26 are joined together at the weld bead WJ. With this configuration, the weld bead WJ and / or hole 26h caused by friction stir welding reach the upper panel 28, thus raising concerns about reduced sealing performance at the hole 26h. However, since the hole 26h is covered with adhesive 42, this concern can be eliminated or reduced.

[0039] In this embodiment, the hole 26h formed in the lower surface 26b of the bottom wall 26 is located directly below the beams 34, 36 that are fixed to the upper surface 26a of the bottom wall 26. With this configuration, while the hole 26h is covered with adhesive 42, the protective panel 38 can be bonded to the portion of the bottom wall 26 of the housing 22 reinforced by the beams 34, 36 using adhesive 42.

[0040] In this embodiment, each weld bead WJ is located directly below the corresponding beam of beams 34 and 36, and extends along the lower surface 26b of the bottom wall 26 in the same direction as the corresponding beam of beams 34 and 36. In friction stir welding, unintended cavities can form not only at the hole 26h used as a tool exit hole, but also in other parts of the weld bead WJ. In this case, if beams 34 and 36 are located directly above the weld bead WJ, the reduction in the sealing performance of the housing 22 due to cavities can be avoided or suppressed by beams 34 and 36. Each weld bead WJ does not need to be completely located directly below the corresponding beam of beams 34 and 36. Each weld bead WJ may be partially located directly below the corresponding beam of beams 34 and 36.

[0041] In this embodiment, beams 34 and 36 of the housing 22 are joined to the bottom wall 26 at welds WJ. In other words, each weld WJ extends from the bottom wall 26 of the housing 22 to a corresponding beam 34 or 36. By employing this technique, friction stir welding can be actively used to join the various components constituting the housing 22.

[0042] Here, we will refer to Figure 4 , Figure 5 and Figure 7 Further description of the protection panel 38. (e.g.) Figure 4 and Figure 5 As shown, the upper surface 37 of the protective panel 38 has a main region 37m and a protruding region 37p projecting upward from the main region 37m. The protruding region 37p of the protective panel 38 is bonded to the lower surface 26b of the bottom wall 26 using an adhesive 42. The main region 37m of the protective panel 38 faces the lower surface 26b of the bottom wall 26 across a gap CL. With this configuration, when the gap CL is formed between the protective panel 38 and the housing 22, the transmission of external forces (i.e., impact loads) applied to the protective panel 38 to the housing 22 can be avoided or suppressed.

[0043] Figure 7 A view of the battery pack 20 is shown below. In other words, Figure 7 The lower surface 39 of the protective panel 38 is shown. (As shown) Figure 7 As shown, the lower surface 39 of the protective panel 38 has a main region 39m and a recessed region 39r that is recessed upward from the main region 39m. In the protective panel 38, the main region 39m of the lower surface 39 is located on the opposite side to the main region 37m of the upper surface 37, and the recessed region 39r of the lower surface 39 is located on the opposite side to the protruding region 37p of the upper surface 37. Figure 7 In the diagram, beams 34 and 36, which are mounted on the upper surface 26a of the bottom wall 26, are indicated by dashed lines. For example... Figure 7As shown, some of the recessed areas 39r are located directly below beams 34 and 36. In other words, in the protective panel 38, as in the case of recessed areas 39r, some of the protruding areas 37p are also located directly below beams 34 and 36.

[0044] Because the sealing performance of the housing 22 is significantly improved, the battery pack 20 in this embodiment can be effectively used as a power source for the electric vehicle 10 traveling on the road.

[0045] In this embodiment, the protective panel 38 can be a component made of metal, such as a component containing aluminum or iron as the main component, rather than a resin component. When the protective panel 38 is a component made of metal (e.g., a component containing aluminum or iron as the main component), the protective panel 38 can be joined using known joining methods (such as welding and fastening) in combination with adhesive 42.

[0046] Embodiments of the present technology have been described in detail above; however, these are merely illustrative and not intended to limit the appended claims. The technology described in the appended claims also covers various variations and modifications from the specific examples described above. The technical elements described in the specification or drawings exhibit technical availability only or in various combinations, and are not limited to the combinations of the claims appended at the time of filing this application. The technology illustrated in the specification and drawings can achieve multiple objectives simultaneously, and has technical availability by achieving one of these objectives.

Claims

1. A battery pack, characterized in that... include: At least one battery cell; A housing that houses the at least one battery cell, the housing having a bottom wall facing the at least one battery cell from below; as well as A protective panel, wherein the protective panel is bonded to the lower surface of the bottom wall of the housing with an adhesive, wherein: A weld bead and a hole exist on the lower surface of the bottom wall of the housing, wherein the weld bead is formed by friction stir welding, and the hole is located at one end of the weld bead; and The hole is covered with the adhesive.

2. The battery pack according to claim 1, characterized in that, At least a portion of the hole is filled with the adhesive.

3. The battery pack according to claim 1, characterized in that, The pores were completely filled with the adhesive.

4. The battery pack according to claim 1, characterized in that: The bottom wall of the housing includes an upper panel and a lower panel facing each other; and The channel for allowing the heat transfer medium to flow is defined between the upper panel and the lower panel.

5. The battery pack according to claim 4, characterized in that, The upper panel and the lower panel are joined together at the weld.

6. The battery pack according to claim 1, characterized in that: The housing also includes a beam fixed to the upper surface of the bottom wall; and The hole formed in the lower surface of the bottom wall is located directly below the beam.

7. The battery pack according to claim 6, characterized in that: The beams of the housing extend along the upper surface of the bottom wall; and At least a portion of the weld bead is located directly below the beam and extends along the lower surface of the bottom wall in the same direction as the beam.

8. The battery pack according to claim 7, characterized in that, The beams of the housing are joined to the bottom wall at the weld.

9. The battery pack according to claim 1, characterized in that: The upper surface of the protective panel has a main area and a protruding area that protrudes upward from the main area; The main region faces the lower surface of the bottom wall of the housing across the gap; and The protruding area is bonded to the lower surface of the bottom wall of the housing using the adhesive.

10. The battery pack according to claim 9, characterized in that: The housing also includes a beam fixed to the upper surface of the bottom wall; and The hole formed in the lower surface of the bottom wall is located directly below the beam and directly above the protruding area of ​​the upper surface of the protective panel.

11. The battery pack according to claim 1, characterized in that: The bottom wall of the casing is made of metal; and The protective panel is made of resin.

12. An electric vehicle that travels on a road surface, characterized in that it comprises: Body; as well as The battery pack according to any one of claims 1 to 11, wherein the battery pack is supported by the vehicle body, wherein The protective panel of the battery pack is exposed to the road surface.

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