Battery unit

Abstract

To suppress interference to a battery even if a load is concentrated to a fragile portion of a frame material.SOLUTION: A battery case 30b comprises a battery frame 40 including a frame material 41 which is formed rectangular and a reinforcement material 45, a bottom material 50 and a lid material 60. The frame material 41 and the reinforcement material 45 consist of a hollow long member having a specific cross-sectional shape. A second frame material 41b includes a first-step reinforcement wall part 403a which vertically partitions the inside thereof, and the reinforcement material 45 includes a second-step reinforcement wall part 403b which vertically partitions the inside thereof. Thickness centers ct1 and ct2 of the first-step reinforcement wall part 403a and the second-step reinforcement wall part 403b are offset in a vertical direction, and a top surface ts2 or a bottom surface bs2 of the second-step reinforcement wall part 403b is positioned between a top surface ts1 and a bottom surface bs1 of the first-step reinforcement wall part 403a in the vertical direction.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The disclosed technology relates to a battery unit that is disposed below a floor panel of a vehicle with battery cells housed in a battery case. [Background technology]

[0002] This type of battery unit is disclosed in Patent Document 1.

[0003] The battery frame 3 of Patent Document 1 has a rectangular outer frame 5 that surrounds multiple batteries 1 arranged vertically and horizontally, and a bottom plate 11 that covers the underside of the batteries 1. A plurality of beam members 9A, 9B, and 9C are installed between a pair of frame members on the sides of the outer frame 5 as reinforcing members.

[0004] Even if a collision load acts on the outer frame 5 from the side, if the load can be properly transmitted to the beam members 9A, 9B, and 9C extending in the direction of the load, the beam members can withstand the load. Therefore, inward deformation of the outer frame 5 can be suppressed, and the battery 1 can be effectively protected. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-118136 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in some cases, such as when colliding with a pillar, a pinpoint load acts on the joint between the beam members of the outer frame. In such cases, the joint is firmly supported on both sides by the beam members, resulting in a so-called three-point bending state. As a result, the load cannot be properly transmitted to the beam members, and the load is concentrated at the point where the load acts, causing the outer frame to deform significantly inward, potentially interfering with the battery.

[0007] One possible solution to this problem is to strengthen the beam members, which act as reinforcing materials, by increasing the number of beam members or their size, but doing so would create new problems, such as a reduction in the internal volume of the battery frame, increased material costs, and an increase in the weight of the battery frame.

[0008] Therefore, this specification discloses a technology that, with a simple ingenuity, can appropriately transmit the load from the frame material to the reinforcing material while suppressing interference with the battery by the frame material even when the load is concentrated and acts on the joint parts of the frame material. [Means for solving the problem]

[0009] The disclosed technology relates to a battery unit that is arranged below a floor panel of a vehicle with battery cells housed in a battery case.

[0010] The battery case includes a battery frame having a rectangular frame member adjacent to the battery cell and surrounding it, and a reinforcing member that is installed between a pair of opposing second frame members parallel to a pair of opposing first frame members, and a base material and a cover material that are assembled to the battery frame and cover the top and bottom of the battery cell.

[0011] The frame material and the reinforcing material are made of hollow, elongated members having specific cross-sectional shapes, and the battery frame is constructed by joining the frame material and the reinforcing material with each wall surface facing up, down, left, and right.

[0012] The second frame member has a first-stage reinforcing wall portion that is parallel to its upper and lower wall surfaces and divides its interior into upper and lower sections, and the reinforcing member has a second-stage reinforcing wall portion that is parallel to its upper and lower wall surfaces and divides its interior into upper and lower sections, the centers of thickness of the first-stage reinforcing wall portion and the second-stage reinforcing wall portion are offset in the vertical direction, and the upper or lower surface of the second-stage reinforcing wall portion is located between the upper and lower surfaces of the first-stage reinforcing wall portion in the vertical direction.

[0013] That is, the disclosed technology is directed to a battery unit that is arranged below a floor panel of a vehicle as a power source for driving, with battery cells housed in a battery case. The battery frame has a rectangular frame member that is adjacent to the battery cells and surrounds them. The battery frame also has a reinforcing member that is installed between one pair of opposing frames of the frame member (a pair of first frame members) and the other pair of opposing frames (a pair of second frame members) in parallel.

[0014] These frame and reinforcing members are made of hollow, elongated members with specific cross-sectional shapes, and the battery frame is constructed by joining the wall surfaces together with their respective orientations. Because they are hollow, elongated members, these frame and reinforcing members are lightweight yet have excellent strength and rigidity. Furthermore, these frame and reinforcing members have first-stage and second-stage reinforcing walls that divide their interiors into upper and lower sections, further enhancing their strength and rigidity.

[0015] The first-stage reinforcing wall portion and the second-stage reinforcing wall portion are offset by a predetermined amount in a state where they overlap in the vertical direction.

[0016] The primary purpose of these first-stage and second-stage reinforcing walls is to reinforce the frame and reinforcing material. Therefore, to efficiently transmit loads, they are typically arranged in series at the same height. This is the general configuration for conventional battery units.

[0017] Furthermore, in order to properly transmit the load, the second-stage side that receives the load requires greater strength and rigidity (for example, 1.2 to 1.5 times) than the first-stage side that transmits the load. Therefore, the thickness of the reinforcing wall portion on the second-stage side is likely to be greater than that on the first-stage side. Also, if the wall is long in the direction in which the load acts, it is prone to bending and deformation, so even greater strength and rigidity are required. Therefore, the second-stage reinforcing wall portion requires greater strength and rigidity than the first-stage reinforcing wall portion. Reinforcing materials are superior in strength and rigidity to frame materials.

[0018] As a result, when a load acts on the joint between two adjacent reinforcement members, such as when a pillar collides, the joint is firmly supported on both sides by the reinforcement members, resulting in a so-called three-point bending state. As a result, the load cannot be properly transmitted to the reinforcement members, causing the frame members to deform significantly inward, which could cause the frame members to interfere with the battery cells.

[0019] In contrast, in this battery unit, the first-stage reinforcing wall and the second-stage reinforcing wall are offset in a partially overlapping state in the vertical direction, so that a predetermined load acting on the first-stage reinforcing wall is transmitted to the reinforcing material, and the remaining load is transmitted to parts other than the second-stage reinforcing wall via the frame material.

[0020] Since the load transmitted to the reinforcing member is reduced, the strength and rigidity required for the reinforcing member can also be reduced. As a result, the thickness of the second-stage reinforcing wall can be reduced. This battery unit can reduce material costs and weight.

[0021] Furthermore, even if a load is applied to the joint due to the reinforcement, the support force of the reinforcement supporting both sides is weakened appropriately, preventing three-point bending. This prevents the frame material from deforming significantly inward and interfering with the battery cells, effectively protecting the battery cells.

[0022] The reinforcing member may be disposed so as to extend in the front-rear direction and assembled to the vehicle.

[0023] This makes it possible to effectively protect the battery cells against a collision load from the front or rear of the vehicle.

[0024] The vehicle may have a pair of front side frames that form a vehicle body together with the floor panel and extend forward from the front side of the floor panel on both sides, and at least a portion of the second frame member located on the front side may be positioned so as to overlap in the vertical direction with the rear ends of both of the front side frames.

[0025] From the perspective of protecting the battery cells, it is best to avoid applying strong loads to the battery unit. However, the need to secure space to install a large-capacity battery unit places restrictions on the vehicle body design, which could result in a decrease in the strength of the vehicle body.

[0026] In contrast, with this battery unit, even if a load acts on the relay portion, the load can be transmitted appropriately while protecting the internal battery cells.

[0027] When a strong collision load acts on the pair of front side frames due to a frontal collision or other event, the front side frames are deformed, and their rear ends are displaced rearward. In this case, if the structure is as described above, the rear ends are received by the second frame member, so part of the collision load can be transmitted to the battery unit. The battery unit can supplement the strength of the vehicle body.

[0028] At least a portion of a front end of the reinforcing member may be disposed at a position overlapping with a rear end of the front side frame in the left-right direction.

[0029] The portions of the battery frame that are reinforced by the reinforcing material have greater strength than other portions, so the above-described configuration allows the load of the front side frame to be efficiently transmitted to the reinforcing material.

[0030] The reinforcing member may be disposed so as to extend in the left-right direction and assembled to the vehicle.

[0031] In such a case, the vehicle may have a pair of side sills that form the body together with the floor panel and extend in the fore-and-aft direction along the left and right side edges of the floor panel, the battery frame may further have a hollow support portion with a rectangular cross section that is integrally formed so as to protrude outward from the frame material, and the battery case may be supported by the pair of side sills via the support portion.

[0032] If the reinforcing material is arranged so as to extend in the left-right direction, the battery cells can be effectively protected against a collision load from the side of the vehicle.

[0033] Furthermore, if the battery frame is supported by a pair of side sills via square pipe-shaped support parts that are integrated with the frame material, the side collision load can be transmitted directly from the side sills to the battery frame.

[0034] Furthermore, the thickness center of at least one of the upper and lower support walls constituting the support portion may be offset in the vertical direction from the thickness center of the first-stage reinforcing wall portion, and the upper or lower surface of the first-stage reinforcing wall portion may be positioned between the upper and lower surfaces of the support wall in the vertical direction.

[0035] This allows the side collision load transmitted through the side sill to be appropriately dissipated and transmitted in a balanced manner from the support to the second frame member, i.e., to the entire battery frame.The thickness of the reinforcing material for the second frame member can be made thinner, which reduces the weight of the battery unit. [Effects of the Invention]

[0036] According to the disclosed technology, a simple modification to the battery unit structure allows the load to be appropriately transmitted from the frame material to the reinforcing material. Even when the load is concentrated at the joints of the frame material, interference with the battery cells by the frame material can be suppressed. This allows for a lightweight battery unit with excellent battery cell protection performance to be provided. It can also be incorporated into part of the collision load transmission mechanism in the vehicle body structure. [Brief explanation of the drawings]

[0037] [Figure 1] 1 is a top view of a vehicle body structure to which the disclosed technology is applied. [Figure 2] FIG. 2 is a perspective view seen from the direction of arrow A in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along the line BB in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along the line DD in FIG. [Figure 5] 5 is a view seen from the direction of arrow E in FIG. 4. [Figure 6] 2 is a cross-sectional view taken along the line CC of FIG. 1. [Figure 7A] FIG. 2 is a diagram illustrating the structure of a battery unit. [Figure 7B] FIG. 2 is a diagram illustrating the structure of a battery unit. [Figure 8] 10A and 10B are diagrams for explaining the detailed structure of a battery unit related to the disclosed technology. [Figure 9A] FIG. 1 is a diagram for explaining a problem in the conventional art (comparison example). [Figure 9B] 10A and 10B are diagrams for explaining a battery unit of an embodiment in comparison with a comparative example. [Figure 10] FIG. 10 is a diagram for explaining a second embodiment of the disclosed technology. DETAILED DESCRIPTION OF THE INVENTION

[0038] The disclosed technology will be described below. However, the description is essentially merely illustrative. The front-rear, left-right, and up-down directions used in the description are based on the vehicle. In each drawing, these directions are indicated by arrows. The left-right direction corresponds to the vehicle width direction.

[0039] <Body structure> 1 to 6 illustrate examples of vehicle body structures to which the disclosed technology is applied. FIG. 1 is a view (plan view) of the vehicle body 1 as seen from above. FIG. 2 is a perspective view as seen from the direction of arrow A in FIG. 1. FIG. 3 is a cross-sectional view taken along the line BB in FIG. 1. FIG. 4 is a cross-sectional view taken along the line DD in FIG. 3. FIG. 5 is a view (bottom view) as seen from the direction of arrow E in FIG. 4. FIG. 6 is a cross-sectional view taken along the line CC in FIG. 1. The vehicle body 1 in these FIGS. 1 to 6 is simplified.

[0040] The vehicle body 1 is composed of a bumper beam 2, a shroud upper member 3, an apron member 4, a front side frame 5, a side sill 6, a dash panel 7, a floor panel 8, and the like.

[0041] This vehicle is an electric vehicle. It is driven by a motor. Although not shown, the motor is mounted in a front space 1a provided at the front of the vehicle body 1. A passenger compartment 1b is formed in the middle of the vehicle body 1. A floor panel 8, which is roughly rectangular in top view, is laid in the middle of the vehicle body 1 so as to extend in both the front-rear and left-right directions (horizontally). The floor panel 8 forms the floor surface of the passenger compartment 1b.

[0042] A battery unit 30 is mounted on a vehicle as a power source for driving a driving motor. The battery unit 30 is required to have high output. Therefore, the battery unit 30 is heavy and has a large capacity. However, the installation space in a vehicle is limited. Therefore, the battery unit 30 is arranged below the floor panel 8 so as to extend along the floor panel 8, as shown by the dashed line in FIG. 1.

[0043] The battery unit 30 of this vehicle has a rectangular appearance when viewed from above, which is substantially the same as the floor panel 8. The battery unit 30 will be described separately below.

[0044] As shown in Fig. 2, the front space 1a and the passenger compartment 1b are separated by a dash panel 7 that extends in both the vertical direction (vertical direction). As shown in Fig. 3, the front end portion of the floor panel 8 is provided with an upwardly inclined surface portion 8a that is inclined so as to become higher toward the front.

[0045] The tip of the upwardly inclined surface portion 8a is connected to the lower end of the dash panel 7. The dash panel 7 and floor panel 8 are integrally formed by joining multiple pressed steel plates. The lower end portion of the dash panel 7 is provided with a protruding strip portion 7a that extends in the left-right direction and protrudes forward.

[0046] A reinforcing rib 7b that forms a closed cross-section structure is provided behind the protruding strip 7a. A bulging portion 8b that bulges upward and extends rearward in a band-like shape is formed in the center of the front end of the floor panel 8. Torque boxes 70 are attached to the left and right sides of the bulging portion 8b on the underside of the floor panel 8, utilizing the upwardly inclined surfaces 8a.

[0047] A pair of side sills 6, 6 with excellent strength and rigidity are provided on both the left and right sides of the center portion of the vehicle body 1. Each side sill 6 is made of a pillar-shaped member and extends parallel to the front-to-rear direction along the left and right side edges of the floor panel 8. A rear side frame 9 extending rearward is connected to the rear end of each side sill 6. A rear floor panel 9a connected to the floor panel 8 is laid between these rear side frames 9, 9.

[0048] As shown in Figures 1, 2, 3, etc., a pair of front side frames 5, 5 extend forward, spaced apart on the left and right sides, from the front side of the floor panel 8. Each front side frame 5 is made of a columnar member with a rectangular cross section, and has a main body portion 5a extending substantially horizontally and a rear end portion 5b extending at a downward incline from the rear end of the main body portion 5a.

[0049] Each front side frame 5 is joined via its rear end 5b to the upwardly inclined surface 8a of the floor panel 8 and to the torque box 70. As shown in Figures 1 and 2, the joint locations of the rear end portions 5b are located midway between the center of the vehicle body 1 and each of the left and right side edges in the left-right direction. The pair of front side frames 5, 5 are arranged at a slight incline so that they widen laterally as they move forward when viewed from the top-bottom direction.

[0050] Suspension housings 11 are provided in front of each of the left and right ends of the dash panel 7. The lower end of each suspension housing 11 is connected to the corresponding front side frame 5. The upper end of each suspension housing 11 is connected to an apron member 4.

[0051] Each apron member 4 extends forward from the outside of each suspension housing 11. Each apron member 4 is curved so that it faces inward in the vehicle width direction as it moves forward. The tips of the pair of apron members 4, 4 are connected by a shroud upper member 3 that extends in the left-right direction.

[0052] A bumper beam 2 extending in the left-right direction is disposed below and forward of the shroud upper member 3. The front ends of the front side frames 5 are connected to both ends of the bumper beam 2 via crash cans 12.

[0053] <Battery unit> 7A and 7B show examples of the structure of the battery unit 30. The battery unit 30 has a plurality of battery cells 30a and a battery case 30b that houses these battery cells 30a.

[0054] Each battery cell 30a is configured by connecting a large number of lithium ion batteries or the like. All of the battery cells 30a are electrically connected and configured to be able to output a predetermined high voltage. Each battery cell 30a is formed in a rectangular block shape (cuboid shape) in consideration of loading efficiency into the battery case 30b. In the case of this battery unit 30, 12 battery cells 30a are arranged inside the battery case 30b so that four are arranged in the left-right direction and three are arranged in the front-rear direction and are closely spaced horizontally.

[0055] The battery case 30b includes a battery frame 40, a base member 50, a lid member 60, etc. The battery frame 40 includes a rectangular frame member 41 that is adjacent to and surrounds a group of densely arranged battery cells 30a, and a plurality of reinforcing members 45. The frame member 41 and the reinforcing members 45 are made of hollow, elongated members with specific cross-sectional shapes. These members have a square pipe shape and are formed by extruding aluminum.

[0056] The battery frame 40 is formed by joining the frame material 41 and the reinforcing material 45 with their wall surfaces facing up, down, left, and right. The detailed structure of the battery unit 30, including the frame material 41 and the reinforcing material 45, will be described separately later.

[0057] The frame member 41 has a pair of first frame members 41a, 41a facing each other laterally and a pair of second frame members 41b, 41b facing each other front-to-rear. Each second frame member 41b has a rectangular cross section with a partitioned interior. Front fastening portions 31 for fastening to the torque box 70 are provided at two predetermined positions symmetrically on the left and right of the front second frame member 41b (also referred to as the front second frame member 41b).

[0058] Meanwhile, each first frame member 41a has an inverted L-shaped cross section with the interior partitioned, and an outward-projecting support portion 42 is integrally formed at its upper portion. Side fastening portions 32 for fastening to the side sill 6 are provided at multiple locations spaced apart in the longitudinal direction of the support portion 42. Additionally, screw fastening portions 33 for screwing the cover member 60 are provided at multiple locations on the frame member 41.

[0059] The reinforcing members 45 also have a rectangular cross section with an interior that is partitioned. In the case of this battery unit 30, there are three reinforcing members 45. Each reinforcing member 45 extends in the front-to-rear direction between and parallel to a pair of first frame members 41a, 41a. Each reinforcing member 45 is installed between the front and rear second frame members 41b, 41b so as to pass between the battery cells 30a.

[0060] The base material 50 and the lid material 60 are made of members formed by pressing aluminum plate material. The base material 50 is joined (welded) to the lower surface of the frame material 41 so as to cover the lower sides of the battery cells 30a. The lid material 60, which covers the upper sides of the battery cells 30a, is fastened to the upper surface of the frame material 41.

[0061] The lid 60 has a tray-like appearance with an opening facing downward. Specifically, when viewed from above, it has a rectangular upper surface 61, a frame-shaped side surface 62 whose upper edge is continuous with the periphery of the upper surface 61, and a flange surface 63 that extends from the lower edge of the side surface 62 around the periphery.

[0062] A platform portion 64 is formed at the rear portion of the lid member 60, extending along the rear edge thereof and having an upper surface portion 61 that is one step higher. This platform portion 64 accommodates electrical components, such as a control device that controls the battery unit 30 and a power input / output device, which are not shown. Side surface portions 62 facing to the left and right are formed to hang down from the upper surface portion 61. On the other hand, the side surface portion 62 facing forward is formed to slope downward toward the front (also referred to as downwardly inclined surface portion 65).

[0063] Fastening holes 66 for screw fastening are formed in multiple locations on the flange surface portion 63, corresponding to the arrangement of the screw fastening portions 33 of the frame material 41. By fastening screws 67 inserted into each fastening hole 66 to the screw fastening portions 33, the lid material 60 is detachably attached to the frame material 41.

[0064] By attaching the cover member 60 to the frame member 41, a step portion 68 that is lower in height than the upper surface of the battery unit 30, i.e., the upper surface portion 61, is formed at the front end portion of the battery unit 30. In detail, the upper surface of the front second frame member 41b and the outer surface of the downwardly inclined surface portion 65 form a step-like portion that is lower in height than the upper surface portion 61 and extends left and right along the front edge of the battery unit 30.

[0065] In this vehicle body structure, by receiving the torque box 70 in this step portion 68, the front end portion of the battery unit 30 and the torque box 70 are arranged to be stacked vertically. This allows the battery unit 30 to be formed into a rectangle that is approximately the same size as the rectangular floor panel 8 when viewed from above. The battery unit 30 can be expanded forward while maintaining the functionality of the torque box 70, resulting in a battery unit 30 with a large capacity.

[0066] <Torque box> When a load acts on the vehicle from the front due to a collision or the like, the load is received by the bumper beam 2. Most of the load received by the bumper beam 2 is transmitted rearward via the left and right crash cans 12, 12 and the pair of front side frames 5, 5.

[0067] The torque box 70 connects the rear end portions 5b of the left and right front side frames 5, 5 to the front end portions of the side sills 6. As a result, the torque box 70 transmits the load acting on the pair of front side frames 5, 5 to the pair of side sills 6, 6.

[0068] Torque box 70 needs to have a predetermined strength and rigidity to properly transmit load. In this vehicle body 1, torque box 70 has a closed cross-sectional structure with excellent strength and rigidity, and is formed by attaching a box panel 71 of a specific shape to the underside of the front end portion of floor panel 8. Torque box 70 cooperates with floor panel 8 to connect rear end portions 5b of each of left and right front side frames 5 to the front end portions of side sills 6.

[0069] There are two box panels 71 in the vehicle body 1. They are formed symmetrically. The left and right box panels 71, 71 are joined and attached to the left and right undersides of the front end portion of the floor panel 8, respectively.

[0070] Each torque box 70 extends relatively long in the left-right direction from the front end portion of the floor panel 8, and has a closed cross-sectional structure with a substantially triangular cross section with a relatively small aspect ratio deviation when viewed from the left-right direction. Therefore, these torque boxes 70 have excellent strength and rigidity.

[0071] As described above, each front side frame 5 is joined via its rear end 5b to the upwardly inclined surface portion 8a of the floor panel 8 and the torque box 70. In detail, as shown in FIGS. 3, 4, and 5, the rear end 5b of each front side frame 5 has a frame joining portion formed to match the shapes of the upwardly inclined surface portion 8a and the front wall of the torque box 70.

[0072] The frame joints are provided with joint flanges 5d that come into surface contact with the upwardly inclined surface 8a and the front wall of the torque box 70. By joining the joint flanges 5d to the upwardly inclined surface 8a and the front wall of the torque box 70, each front side frame 5 is connected to the floor panel 8 and the torque box 70.

[0073] That is, each torque box 70, which has a closed cross-sectional structure with excellent strength and rigidity, cooperates with the floor panel 8 to connect the rear end portion 5b of each of the left and right front side frames 5 to the front end portion of the side sill 6. Therefore, when a load acts on each front side frame 5 from the front, the load can be effectively transmitted to each torque box 70. The load acting on each torque box 70 can then be effectively transmitted to each side sill 6. This allows the torque boxes 70 to fully function.

[0074] A step 68 is provided at the front end portion of the battery unit 30. The step 68 is formed to fit along the bottom wall and rear wall of each torque box 70. As a result, the front end portion of the battery unit 30 and each torque box 70 are arranged to overlap vertically with a small clearance C. This gives the battery unit 30 a rectangular shape that is approximately the same size as the floor panel 8 when viewed from above. As a result, the battery unit 30 is supported by the pair of torque boxes 70, 70 and the pair of side sills 6, 6, which have excellent strength and rigidity.

[0075] 3 and 6, a bolt support tube 31a that passes through the front second frame member 41b in the vertical direction is attached to the front fastening portion 31. The upper end portion of the bolt support tube 31a protrudes from the upper surface of the front second frame member 41b. The bolt 31b inserted through the bolt support tube 31a is fastened to a fastening seat 72 provided on the bottom wall of each torque box 70.

[0076] Although not shown here, each side fastening portion 32 provided on the support portion 42 of the first frame member 41a is configured similarly to the front fastening portion 31. That is, bolts 32b inserted into the bolt support pipes of each side fastening portion 32 are fastened to each side sill 6. By doing so, the lower surface of the floor panel 8 including the torque box 70 and the upper surface of the battery case 30b including the frame member 41 and the lid member 60 face each other with a predetermined gap (clearance C) between them.

[0077] <Detailed structure of the battery unit> 8 shows a main part (a connecting portion between the reinforcing member 45 and the frame member 41) of the battery unit 30 in order to specifically explain the disclosed technology. Here, the connecting portion of the second frame member 41b of the frame member 41 is illustrated as an example.

[0078] As described above, the frame material 41 and the reinforcing material 45 are made of hollow, elongated members formed by extruding aluminum, and have specific cross-sectional shapes. That is, the cross-sectional shapes (both short and long directions) of the frame material 41 and the reinforcing material 45 are the same over their entire lengths.

[0079] The frame member 41 and the reinforcing member 45 each have a pair of first wall surfaces 401, 401 facing each other vertically, and a pair of second wall surfaces 402, 402 facing each other front-to-back or left-to-right along both edges of the first wall surfaces 401, 401. The pair of second wall surfaces 402, 402 of the second frame member 41b face each other front-to-back, and the pair of second wall surfaces 402, 402 of the reinforcing member 45 face each other left-to-right.

[0080] With the end face of the reinforcing member 45 butted against the side face of the second frame member 41b, the peripheral portion of the end face of the reinforcing member 45 is joined (welded) to the second frame member 41b, thereby connecting them. For example, the second frame member 41b and the reinforcing member 45 can be positioned in the up-down direction by adjusting the positions of their first wall surfaces 401 (surface alignment).

[0081] That is, the vertical widths (distance between the upper and lower surfaces) of the pair of first wall surfaces 401, 401 of the frame material 41 and the reinforcing material 45 are approximately the same. Only one of the surfaces may be flush-fitted. Also, the vertical positions of the frame material 41 and the reinforcing material 45 may be adjusted by a concave-convex fit or the like. A structure (positioning structure) is provided between the frame material 41 and the reinforcing material 45 that can easily achieve appropriate vertical positioning thereof.

[0082] Inside these frame material 41 and reinforcing material 45, reinforcing wall portions 403 are provided that run parallel to the upper and lower first wall surfaces 401, 401 and divide the interior into upper and lower sections (the reinforcing wall portion 403 of the second frame material 41b is also referred to as the first-stage reinforcing wall portion 403a, and the reinforcing wall portion 403 of the reinforcing material 45 is also referred to as the second-stage reinforcing wall portion 403b). The first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b are arranged at positions that divide the first wall surface 401 approximately in half in the vertical direction.

[0083] 8 shows the cross-sectional shape (cross-sectional shape seen from the short side direction) of the second frame member 41b and the vertical cross-sectional shape (cross-sectional shape seen from the long side direction) of the reinforcing member 45. The thicknesses of the first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b are approximately the same throughout the frame member 41 and the reinforcing member 45 (with differences of the order of tolerance).

[0084] Based on the difference in length in the transmission direction (front-rear direction here) of a particularly important load (load from the front here), the second-stage reinforcing wall portion 403b is thicker than the first-stage reinforcing wall portion 403a. In other words, compared to the second frame member 41b to which the main load is applied in the short direction, the reinforcing member 45 to which the load is applied in the long direction is required to have greater strength and rigidity.

[0085] The main purpose of these reinforcing wall portions 403a, 403b is to reinforce the frame material 41 and the reinforcing material 45. Therefore, the first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b are usually arranged at the same height and connected in series so that the load can be efficiently transmitted. This is the general configuration for conventional battery units.

[0086] In contrast, in this battery unit 30, by applying the disclosed technology, the vertical arrangement is intentionally designed to be slightly offset, as shown in the enlarged view of Fig. 8. Specifically, the first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b are configured such that the thickness centers ct1, ct2 of the first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b are offset in the vertical direction, and the upper surface ts2 or the lower surface bs2 of the second-stage reinforcing wall portion 403b is positioned between the upper surface ts1 and the lower surface bs1 of the first-stage reinforcing wall portion 403a in the vertical direction.

[0087] Here, the first-stage reinforcing wall portion 403a is offset from the second-stage reinforcing wall portion 403b so that the thickness center ct1 of the first-stage reinforcing wall portion 403a is located above the thickness center ct2 of the second-stage reinforcing wall portion 403b (indicated by Δh in FIG. 8). Thus, the second-stage reinforcing wall portion 403b is disposed so that the upper surface ts2 of the second-stage reinforcing wall portion 403b is located between the upper surface ts1 and the lower surface bs1 of the first-stage reinforcing wall portion 403a (see the extended dashed line s-s in FIG. 8).

[0088] Furthermore, the lower surface bs1 of the first-stage reinforcing wall portion 403a is located above the thickness center ct2 of the second-stage reinforcing wall. Note that the offset direction may be downward, and the lower surface bs2 of the second-stage reinforcing wall portion 403b may be positioned between the upper surface ts1 and the lower surface bs1 of the first-stage reinforcing wall portion 403a. In this case, the upper surface ts1 of the first-stage reinforcing wall portion 403a may be located below the thickness center ct2 of the second-stage reinforcing wall.

[0089] Given their functions, the first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b generally extend parallel to the horizontal direction. Depending on the specifications, they may be slightly curved or inclined. However, if the purpose is reinforcement, these differences in shape do not affect the results.

[0090] At least, the first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b should be configured so as to have such an arrangement in the vicinity of the joint portion between them, as shown in an enlarged view at the bottom of Figure 8. More specifically, at the joint portion between the first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b, the joined ends thereof are arranged so as to be approximately parallel to each other.

[0091] Incidentally, even in conventional battery units, such an arrangement may occur accidentally. However, in the disclosed technology, the frame member 41 and the reinforcing member 45 are deliberately configured to always stably maintain such an arrangement. For example, the positioning structure described above is one way to achieve this.

[0092] By devising such a configuration that the frame material 41 and the reinforcing material 45 are slightly offset vertically, it is possible to appropriately transmit the load from the frame material 41 to the reinforcing material 45. Even when a load is concentrated on the joint portion of the frame material 41, it is possible to suppress interference of the frame material 41 with the battery cells 30a. This makes it possible to provide a lightweight battery unit 30 that has excellent performance in protecting the battery cells 30a.

[0093] This point will be explained with reference to Figures 9A and 9B. Figure 9A shows the structure of a conventional battery unit 100 (conventional example) given as a comparative example. Figure 9B shows the structure of a battery unit 30 in this embodiment to which the disclosed technology is applied.

[0094] The battery units 100, 30 are required to protect the internal battery cells 30a against loads acting from the outside due to a collision or the like. The frame material 41 receives the load first. The load is then transmitted to the reinforcing material 45. In order to suppress excessive deformation and transmit the load appropriately, the reinforcing material 45 (second stage) to which the load is transmitted next is required to have greater strength and rigidity than the frame material 41 (first stage) that receives the load first (for example, 1.2 to 1.5 times). Therefore, the reinforcing wall portion 403 of the second stage is likely to be thicker than that of the first stage.

[0095] The length in the direction in which the load acts also has an effect. If the length is long in the direction in which the load acts, the reinforcing member 45 is more likely to bend and deform. If the reinforcing member 45 bends, it may interfere with the battery cell 30a. Therefore, the reinforcing member 45 is required to have even greater strength and rigidity.

[0096] In particular, in the case of the battery units 100 and 30, the length in the direction in which the load acts is overwhelmingly longer than that of the reinforcing member 45, so it is unavoidable that the thickness of the second-stage reinforcing wall portion 403b is increased. Therefore, in the conventional structure, as shown in Fig. 9A, the thickness of the second-stage reinforcing wall portion 403b is increased so that the load acting from the second frame member 41b can be appropriately received and transmitted.

[0097] However, as shown in the lower diagram of Figure 9A, when a column P collides, there are cases where a load acts precisely on the joint between two adjacent reinforcing members 45, that is, on the part that is not reinforced by the reinforcing members 45. In such cases, because both sides of the joint are firmly supported by the reinforcing members 45, a so-called three-point bending state occurs.

[0098] As a result, the load cannot be properly transmitted to the reinforcing material 45, and the load is concentrated at the portion where the load acts. As a result, the frame material 41 is significantly deformed inward, and there is a risk that the frame material 41 may interfere with the battery cell 30a.

[0099] In contrast, as shown in Fig. 9B, in the battery unit 30 to which the disclosed technology is applied, the first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b are intentionally arranged with their positions shifted in the vertical direction. In detail, as shown in the upper diagram of Fig. 9B, the first-stage reinforcing wall portion 403a and the second-stage reinforcing wall portion 403b are offset in the vertical direction while partially overlapping each other.

[0100] As a result, as shown by arrows A1 to A3 in Figure 9B, of the load A1 acting on the first-stage reinforcing wall portion 403a, a predetermined proportion of the load A2 is transmitted to the reinforcing material 45, and the remaining load A3 is transmitted to a portion other than the second-stage reinforcing wall portion 403b via the frame material 41.

[0101] As described above, conventional reinforcing members 45 are required to have strength and rigidity that are 1.2 to 1.5 times that of the frame member 41, which is the source of the load. In contrast, in this battery unit 30, the load transmitted to the reinforcing member 45 is reduced, so the strength and rigidity required of the reinforcing member 45 can also be reduced. Accordingly, the thickness of the reinforcing wall portion 403 can be made thinner. The reinforcing member 45 is designed to have approximately the same strength and rigidity as the frame member 41 (1x). This battery unit 30 can reduce material costs and weight.

[0102] 9B, even if a load acts on the joint portion at a pinpoint due to the reinforcing material 45, the supporting force of the reinforcing material 45 supporting both sides of the joint portion is weakened appropriately, so that a three-point bending state can be avoided. This prevents the frame material 41 from significantly deforming inward and interfering with the battery cell 30a.

[0103] By applying the disclosed technology, the battery unit 30 can appropriately transmit a load to the reinforcing member 45 while mitigating the concentration of the load at the load acting portion. In other words, the load can be transmitted from the frame member 41 to the reinforcing member 45 while being appropriately dispersed, regardless of the acting portion. The entire frame member 41 and the reinforcing member 45 deform appropriately to absorb the load. Therefore, the battery cells 30a can be effectively protected.

[0104] Furthermore, this battery unit 30 can also be incorporated into a part of a transmission mechanism for the load (collision load) acting on the vehicle body 1.

[0105] For example, as described above, when a load acts on the vehicle from the front, much of the load is transmitted rearward via the bumper beam 2, the crash cans 12, 12, the pair of front side frames 5, 5, the first torque box 70, 70, and the pair of side sills 6, 6.

[0106] From the viewpoint of protecting the battery cells 30a, it is desirable to avoid a strong load from acting on the battery unit 30. However, the need to secure space for mounting a large-capacity battery unit 30 places restrictions on the design of the vehicle body 1. This may result in a decrease in the strength of the vehicle body 1.

[0107] In contrast, with this battery unit 30, even if a load acts on the joint portion, the load can be appropriately transmitted while protecting the internal battery cells 30a. Therefore, the battery unit 30 can be incorporated into part of the collision load transmission mechanism of the vehicle body 1, thereby complementing the strength of the vehicle body 1.

[0108] Specifically, as shown in Figures 3 and 4, each front side frame 5 has, at its rear end 5b, downward protrusions 410 located below the torque box 70. The upper part of the front second frame member 41b is positioned so as to overlap these downward protrusions 410 in the up-down direction when viewed from the front-rear and left-right directions. In other words, each downward protrusion 410 is positioned so that its lower end is located below the upper surface of the front second frame member 41b. Each downward protrusion 410 faces the front-rear second frame member 41b with a small gap between them.

[0109] When a strong collision load acts on the pair of front side frames 5, 5 due to a front collision or the like, the front side frames 5 are deformed. Then, their rear ends 5b are displaced rearward. At that time, the downward protrusions 410 are received by the front second frame members 41b, so that part of the collision load can be transmitted to the battery unit 30.

[0110] The battery unit 30, together with the pair of torque boxes 70, 70, can transmit a collision load to the pair of side sills 6, 6 via the battery frame 40. Because the collision load can be distributed and transmitted between the two, the burden on the torque boxes 70 can be reduced. The battery unit 30 can supplement the strength of the vehicle body 1.

[0111] In this case, it is preferable that at least a part of the front end of the reinforcing member 45 is disposed at a position that overlaps in the left-right direction with the rear end 5b of the front side frame 5 when viewed in the front-rear direction.

[0112] As described above, by applying the disclosed technology, interference of the frame material 41 with the battery cells 30a can be suppressed even when a load is concentrated on the joint portion of the frame material 41. Therefore, the rear end portion 5b of the front side frame 5 can be positioned at any position on the frame material 41.

[0113] However, within the battery frame 40, the portions reinforced by the reinforcing material 45 are stronger than other portions. Therefore, by arranging the downward protrusions 410 in positions where they at least partially overlap the front ends of the reinforcing material 45 in the left-right direction, the load of the front side frames 5 can be efficiently transmitted to the reinforcing material 45. The collision load due to a frontal collision can be transmitted to each side sill 6 while effectively protecting the battery cells 30a.

[0114] <Second embodiment> 10 illustrates a second embodiment of the disclosed technology. In this embodiment, the orientation of the reinforcing member 45 of the battery unit 30 differs from that of the above-described embodiment. Except for this, the basic configuration of this embodiment is the same as that of the above-described embodiment.

[0115] For example, the vehicle body 1, the battery cells 30a of the battery unit 30, the cover material 60, the base material 50, etc. are the same as those in the above-described embodiment. Therefore, only the differences will be specifically described, and descriptions of other configurations will be omitted.

[0116] In the case of the battery unit 30 (also referred to as the second battery unit 300) of this embodiment, when assembled to a vehicle, the reinforcing material 45 is arranged to extend in the left-right direction.

[0117] That is, in the above-described battery unit 30, the frame material 41 has a pair of first frame materials 41a, 41a facing each other laterally and a pair of second frame materials 41b, 41b facing each other front-to-rear. In contrast, in the case of the second battery unit 300, a pair of horizontal frame materials 301, 301 (corresponding to the first frame material 41a) face each other front-to-rear, and a pair of vertical frame materials 302, 302 (corresponding to the second frame material 41b) face each other left-to-right.

[0118] The second battery unit 300 has two reinforcing members 45 (also referred to as horizontal reinforcing members 303). Each horizontal reinforcing member 303 extends in the left-right direction between and parallel to a pair of horizontal frame members 301, 301. Each horizontal reinforcing member 303 is installed between the left and right vertical frame members 302 so as to pass between the battery cells 30a.

[0119] In the case of the second battery unit 300, the interior of the vertical frame member 302 and the horizontal reinforcement member 303 is divided into three sections. Specifically, the vertical frame member 302 has a pair of first-stage reinforcing wall portions 403a, 403a (also referred to as the upper first-stage reinforcing wall portion 304 and the lower first-stage reinforcing wall portion 305) spaced apart from each other above and below. The horizontal reinforcement member 303 has a pair of second-stage reinforcing wall portions 403b, 403b (also referred to as the upper second-stage reinforcing wall portion 306 and the lower second-stage reinforcing wall portion 307) spaced apart from each other above and below.

[0120] Furthermore, the upper first-stage reinforcing wall portion 304 and the upper second-stage reinforcing wall portion 306, and the lower first-stage reinforcing wall portion 305 and the lower second-stage reinforcing wall portion 307 are offset in a state where they partially overlap in the vertical direction, similar to the previous battery unit 30.

[0121] Furthermore, in the case of the second battery unit 300, the support portion 42 (also referred to as the second support portion 310) provided on each vertical frame member 302 is formed as a hollow portion with a rectangular cross section. Specifically, the second support portion 310 has a pair of support walls 311 (an upper support wall portion 311a and a lower support wall portion 311b) that protrude horizontally from the side surface of the vertical frame member 302 and face each other vertically, and an end wall portion 312 that continues to the tip of these support walls 311a and 311b.

[0122] That is, the second support portion 310 is configured by integrating a square pipe-shaped portion with the vertical frame material 302. Therefore, it is possible to reduce the weight and it is also excellent in strength and rigidity.

[0123] The side fastening portions 32 for fastening to the side sill 6 are provided at three locations corresponding to the positions of the front horizontal frame member 301 and each horizontal reinforcement member 303. Specifically, each side fastening portion 32 is disposed at a position overlapping or in the vicinity of the end of the front horizontal frame member 301 and each horizontal reinforcement member 303 in the front-rear direction when viewed from the top-bottom or left-right directions.

[0124] The side fastening portion 32 is composed of through holes formed in the upper support wall portion 311a and the lower support wall portion 311b, and second bolt support pipes 313 installed to communicate with these through holes. Bolts inserted into the second bolt support pipes 313 are fastened to the side sills 6. This fixes the vertical frame members 302 to the side sills 6.

[0125] A collision load due to a side collision acting on the side sill 6 is transmitted to the battery frame 40 via each side fastening portion 32. Therefore, the collision load can be efficiently transmitted to the transverse reinforcement member 303. The collision load due to a side collision can be transmitted to the vehicle body 1 via the battery frame 40 while effectively protecting the battery cells 30a.

[0126] It is preferable that the thickness centers ct3u, ct3d of at least one of the upper support wall portion 311a and the lower support wall portion 311b are offset in the vertical direction from the thickness centers ct1u, ct1d of the upper first-stage reinforcing wall portion 304 and / or the lower first-stage reinforcing wall portion 305, and that the upper or lower surface of the first-stage reinforcing wall portion 403a is positioned between the upper and lower surfaces of that (these) support wall portion 311 in the vertical direction.

[0127] 10, the thickness center ct3u of the upper support wall portion 311a is offset upward with respect to the thickness center ct1u of the upper first-stage reinforcing wall portion 304, and the upper surface of the upper first-stage reinforcing wall portion 304 is located between the upper surface ts3u and the lower surface bs3u of the upper support wall portion 311a in the vertical direction. Similarly, the thickness center ct3d of the lower support wall portion 311b is offset upward with respect to the thickness center ct1d of the lower first-stage reinforcing wall portion 305, and the upper surface of the lower first-stage reinforcing wall portion 305 is also located between the upper surface ts3d and the lower surface bs3d of the lower support wall portion 311b in the vertical direction.

[0128] The offset direction may be downward, and the lower surface of the upper first-stage reinforcing wall portion 304 or the like may be positioned between the upper and lower surfaces of the upper support wall portion 311a or the like.

[0129] This allows the load, which is transmitted in three stages in this order: second support section 310, vertical frame member 302, and horizontal frame member 301, to be transmitted to these members while being appropriately relieved. This eliminates the need to make the vertical frame members stronger than the support sections, and the horizontal frame members even stronger than the vertical frame members, as in the past, and allows the thickness of the reinforcing walls of the vertical and horizontal frame members to be thinner. This allows the battery unit to be lighter without compromising the protective performance of the battery cells.

[0130] The disclosed technology is not limited to the above-described embodiment, but includes various other configurations. For example, although an electric vehicle is used as an example of the vehicle in the embodiment, the vehicle may be a hybrid vehicle. The vehicle body structure, including the box panel 71, and the detailed shapes of the battery units 30, 300 can be modified as needed depending on the specifications as long as the application of the disclosed technology is not affected.

[0131] The number of first-stage reinforcing wall portions 403a and second-stage reinforcing wall portions 403b provided may be three or more. The inside of the support portion 42, 310 may also be reinforced with reinforcing wall portions 403. The frame material and reinforcing material may be die-cast products. [Explanation of symbols]

[0132] 1. Body 2 bumper beams 3 Shroud upper member 4 Apron Members 5 Front side frame 5a Main body 5b Rear end 6 Side sill 7 Dash Panel 8 Floor Panels 8a Uphill slope 8b Bulge 12 Crush Can 30 Battery Unit 30a battery cell 30b Battery Case 40 Battery Frame 41 Frame material 41a 1st frame material 41b 2nd frame material 42 Support part 45 Reinforcement 50 Bottom material 60 Lid material 65 Downward slope section 68 Step 70 Torque box 401 First Wall 402 Second wall 403 Reinforced wall 403a One-piece reinforced wall 403b Two-section reinforcement wall section 410 Lower protrusion

Claims

1. A battery unit that is disposed under a floor panel of a vehicle with battery cells housed in a battery case, The battery case includes: a battery frame including a rectangular frame member adjacent to the battery cell so as to surround the battery cell, and a reinforcing member disposed between a pair of opposing second frame members of the frame members in parallel with a pair of opposing first frame members; a bottom material and a cover material that are assembled to the battery frame and cover the top and bottom of the battery cell; Equipped with The frame material and the reinforcing material are made of hollow elongated members having specific cross-sectional shapes, and the battery frame is configured by joining the frame material and the reinforcing material with each wall surface facing up, down, left, and right, The second frame member has first-stage reinforcing wall portions parallel to its upper and lower wall surfaces to divide its interior into upper and lower sections, and the reinforcing member has second-stage reinforcing wall portions parallel to its upper and lower wall surfaces to divide its interior into upper and lower sections, A battery unit characterized in that the thickness centers of the first-stage reinforcing wall portion and the second-stage reinforcing wall portion are offset in the vertical direction, and the upper or lower surface of the second-stage reinforcing wall portion is located between the upper and lower surfaces of the first-stage reinforcing wall portion in the vertical direction.

2. 2. The battery unit according to claim 1, The battery unit is assembled to the vehicle with the reinforcing member disposed so as to extend in the front-rear direction.

3. 3. The battery unit according to claim 2, The vehicle includes a pair of front side frames that form a vehicle body together with the floor panel and extend forward from a front side of the floor panel at a distance on the left and right, A battery unit is arranged in a position where at least a portion of the second frame member located on the front side overlaps with the rear ends of both of the front side frames in the vertical direction.

4. The battery unit according to claim 3, The battery unit is arranged in a position where at least a portion of a front end portion of the reinforcing material overlaps with a rear end portion of the front side frame in the left-right direction.

5. 2. The battery unit according to claim 1, The battery unit is assembled to the vehicle with the reinforcing member disposed so as to extend in the left-right direction.

6. 6. The battery unit according to claim 5, The vehicle includes a pair of side sills that form a vehicle body together with the floor panel and extend in a front-rear direction along both left and right side edges of the floor panel, The battery frame further includes a hollow support portion having a rectangular cross section that is integrally formed with the frame material so as to protrude outward, The battery unit has the battery case supported by the pair of side sills via the support portions.

7. 7. The battery unit according to claim 6, A battery unit in which the thickness center of at least one of the upper and lower support walls constituting the support portion is offset in the vertical direction from the thickness center of the first-stage reinforcing wall portion, and in the vertical direction, the upper surface or lower surface of the first-stage reinforcing wall portion is located between the upper and lower surfaces of the support wall.

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