Battery unit for vehicle

Abstract

To provide a battery unit of a vehicle capable of efficiently receiving an input impact load by a part other than a battery cell while avoiding increase in size and weight of a battery storage case.SOLUTION: The battery unit includes a battery module and a battery housing case. The battery housing case includes a pair of frame members and a plurality of cross members. Both end portions of the cross member in the extension direction are connected to the pair of frame members. The module case is provided with cover walls respectively connected to two adjacent cross members. At least one of the cross members has a multiple rib structure and a single rib portion. In the multiple rib structure portion, the ribs are branched into a plurality of ribs from one end side toward the other end side and then merged into one rib again. An end portion of the single rib portion in the extending direction is connected to the multiple rib structure portion. The end edge of the cover wall is connected to the vicinity of a portion where the number of ribs of the multiple rib structure changes from a plurality to one.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a vehicle battery unit in which a battery module is housed in a battery housing case. [Background technology]

[0002] BACKGROUND ART A known vehicle battery unit has a plurality of battery cells housed in a battery housing case, which is attached to a frame member of the vehicle (see, for example, Patent Document 1).

[0003] The vehicle battery unit described in Patent Document 1 includes a battery module containing a plurality of stacked battery cells, and a battery housing case that houses the battery module. The battery housing case includes a bottom wall member on the top surface of which the battery module is placed, and a plurality of frame members that are connected to the top surface of the bottom wall member and surround the outside of the battery module.

[0004] The battery unit of the vehicle described in Patent Document 1 has multiple frame members connected to a bottom wall member so as to surround the outside of the battery module, so that when an impact load is input from the outside, the frame members can protect the battery module (battery cell) on the bottom wall member. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-106283 Summary of the Invention [Problem to be solved by the invention]

[0006] The vehicle battery unit described in Patent Document 1 is structured so that when an external impact load is applied, the load is received by the frame members of the battery housing case. Therefore, in order to reliably protect the battery cells housed in the battery housing case from the input of the impact load, it is necessary to increase the number of frame members or make the frame members larger. However, this causes the battery housing case to become larger and heavier, so improvements are desired.

[0007] Therefore, the present invention aims to provide a vehicle battery unit that can efficiently absorb input impact loads with parts other than the battery cells while avoiding an increase in the size and weight of the battery housing case, and ultimately contributes to improving the energy efficiency of the vehicle by making the battery housing case smaller and lighter. [Means for solving the problem]

[0008] In order to solve the above problems, the vehicle battery unit according to the present invention employs the following configuration. That is, the battery unit of the vehicle according to the present invention includes a battery module (e.g., battery module 7 in the embodiment) in which battery cells (e.g., battery cell 6 in the embodiment) are housed in a module case (e.g., module case 40 in the embodiment), and a battery housing case (e.g., battery housing case 10 in the embodiment) attached to a vehicle frame member (e.g., side sill 3 in the embodiment) and housing the battery module therein, and the battery housing case includes a pair of frame members (e.g., frame member 11 in the embodiment) extending along a first direction substantially perpendicular to the vertical direction, and a plurality of cross members (e.g., first cross member 12f, second cross member 12f in the embodiment) extending along a second direction substantially perpendicular to the vertical direction and the first direction, with both ends in the extension direction connected to the pair of frame members. and a third cross member 12s, and a third cross member 12t, the module case comprising a cover wall (e.g., cover wall 42 in the embodiment) that covers the upper part of the battery cell and has both edge portions in the first direction connected to the two adjacent cross members, and at least one of the adjacent cross members has a multi-rib structure portion (e.g., multi-rib structure portion 51 in the embodiment) in which a rib (e.g., rib 50 in the embodiment) branches from one end side to the other end side in the second direction into multiple ribs and then merges again into one rib, and a single rib portion (e.g., single rib portion 52 in the embodiment) that extends along the second direction and has an end portion in the extending direction connected to the multi-rib structure portion, and the edge of the cover wall is connected near the portion where the number of ribs in the multi-rib structure portion changes from multiple to one.

[0009] In this battery unit, both edges of the cover wall of the battery module in the first direction are connected to two adjacent cross members. Therefore, when an impact load is input to one frame member from one side in the second direction, the impact load transmitted to one of the adjacent cross members is efficiently transmitted to the other cross member through the cover wall. As a result, the input impact load is efficiently distributed and supported by the multiple cross members through the cover wall. In particular, in this embodiment, at least one of the adjacent cross members has a multi-rib structure portion and a single rib portion interconnected in the second direction, and the edge of the cover wall is connected near a portion of the multi-rib structure portion where the number of ribs changes from multiple to one. Therefore, an impact load transmitted to the multi-rib structure portion of the cross member is transmitted to the cover wall through a portion that is relatively susceptible to outward movement in response to the input load. As a result, an impact load input to one cross member is efficiently transmitted to the other cross member through the cover wall. Therefore, when this configuration is adopted, it is possible to efficiently absorb an input impact load using the cover wall without increasing the number of cross members or enlarging the cross members.

[0010] The cross member having the multiple rib structure portion and the single rib portion may be provided with a widening portion (e.g., widening portion 45 in the embodiment) in which the width in the first direction gradually increases in a fan-out manner toward the fixing portion with the skeletal member (e.g., fixing portion 44 in the embodiment).

[0011] In this case, an impact load input to one of the skeletal members from one side in the second direction is transmitted from the fixed portion of the cross member to the skeletal member through the widened portion to the multi-rib structure and the individual rib portion. Because the widened portion's width in the first direction gradually decreases from the fixed portion to the skeletal member toward the multi-rib structure and the individual rib portion, the load input from the skeletal member to the cross member is easily transmitted to the multi-rib structure and the individual rib portion. Therefore, an impact load input to one cross member is easily transmitted to the other cross member through the cover wall. Furthermore, an impact load input from one side of one cross member is transmitted to the other frame member through the widened portion on the other side of the cross member. At this time, the widened portion on the other side gradually increases in width in the first direction toward the fixed portion with the other frame member, so the impact load is stably received over a wide area of ​​the other frame member in the first direction. Therefore, when this configuration is adopted, it becomes possible to more efficiently absorb the input impact load by portions other than the battery cells.

[0012] Near the area where the number of ribs in the multi-rib structure portion of the cross member changes from multiple to one, a connection portion (e.g., fastening boss portion 54 in the embodiment) to the cover wall may be provided via multiple reinforcing ribs (e.g., reinforcing rib 53 in the embodiment) extending along the first direction.

[0013] In this case, multiple reinforcing ribs extend from the multi-rib structure of the cross member in a direction perpendicular to the extension direction of the cross member, and the multiple reinforcing ribs are connected to the cover wall, so that impact loads input to the multi-rib structure of the cross member can be efficiently transmitted to the cover wall via the multiple reinforcing ribs.

[0014] A separation space (for example, separation space S in the embodiment) may be provided between the skeletal member and the battery module, the space being spaced apart in the second direction.

[0015] In this case, when an impact load is applied to one of the skeletal members from one side in the second direction, the impact load is absorbed by the cross member and the cover wall of the battery module. Even if a portion of one of the skeletal members is displaced in the second direction, the load is unlikely to be directly transmitted from the skeletal member to the battery module because a separation space is secured between the skeletal member and the battery module. Therefore, when this configuration is adopted, it is possible to more effectively protect the battery cells when an impact load is applied.

[0016] The two adjacent cross members may be arranged so that the coupling portions (for example, the fastening boss portions 54, 65 in the embodiment) with respect to the cover wall are provided at positions offset from each other in the second direction.

[0017] In this case, when an impact load is input to one of the frame members from one side in the second direction, the load is absorbed by the two adjacent cross members and also by the cover wall. At this time, the connecting portions where the load is transmitted from the two cross members to the cover wall are positioned at positions offset from each other in the second direction. This makes it difficult for the cover wall to bend or deform when an impact load is input, allowing the cover wall to efficiently absorb the impact load. [Effects of the Invention]

[0018] The vehicle battery unit according to the present invention can efficiently absorb input impact loads by portions other than the battery cells while avoiding an increase in the size and weight of the battery housing case. Therefore, when the battery unit according to the present invention is adopted, the overall size and weight of the battery housing case can be reduced, thereby contributing to improved energy efficiency of the vehicle. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing a structure of a lower part of a vehicle body of an embodiment; [Figure 2] FIG. 2 is a plan view of the battery unit according to the embodiment. [Figure 3] FIG. 3 is an enlarged plan view of a part of the battery unit shown in FIG. 2. [Figure 4] An enlarged view of part IV in Figure 3. [Figure 5] 4 is a plan view of a portion of the third cross member according to the embodiment, which corresponds to the portion V in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the present invention will be described below with reference to the drawings. In the drawings, an arrow FR pointing forward of the vehicle 1, an arrow UP pointing upward of the vehicle 1, and an arrow LH pointing to the left side of the vehicle 1 are shown at appropriate locations.

[0021] Fig. 1 is a diagram showing the underbody structure of a vehicle 1. Fig. 1 is a cross-sectional view of the underbody of the vehicle 1 cut in a direction perpendicular to the longitudinal direction of the vehicle body. A pair of side sills 3, which are vehicle body framework members extending generally along the longitudinal direction of the vehicle, are disposed at lower positions on both sides of the vehicle interior 2 in the vehicle width direction. Only one of the side sills 3 is shown in FIG. 1. A floor panel 4 is mounted on the left and right side sills 3. A battery unit 5 is disposed below the floor panel 4 so as to generally follow the underside of the floor panel 4. The battery unit 5 includes a battery module 7 that houses a plurality of stacked battery cells 6 (see FIG. 2), and a battery housing case 10 that is attached to the left and right side sills 3 of the vehicle and houses the plurality of battery modules 7 inside.

[0022] The battery housing case 10 includes a case main body 25 on the upper surface of which are mounted a plurality of battery modules 7 (battery cells 6) and control devices (not shown), and a cover member 30 that covers the upper part of the case main body 25. The case body 25 is formed in a substantially rectangular shape in a plan view. The left and right side edges of the case body 25 are fixed to the lower surfaces of the corresponding left and right side sills 3 by fastening members (not shown).

[0023] The side sill 3 is configured by sandwiching a stiffener 3C between a hat-shaped side sill inner 3A and a side sill outer 3B. The side sill inner 3A and the side sill outer 3B have upper and lower joining flanges 3Af, 3Bf. The upper and lower joining flanges 3Af, 3Bf of the side sill inner 3A and the side sill outer 3B are arranged opposite each other. The mutually opposing joining flanges 3Af, 3Bf are connected by welding or the like with the stiffener 3C sandwiched between them. The side sill inner panel 3A has an inner bulge portion 3Ac with a U-shaped cross section that bulges inward in the vehicle width direction from the base of the upper and lower joining flanges 3Af, 3Bf. The left and right side edges of the case body 25 are connected to the underside of the inner bulge portion 3Ac of the side sill inner panel 3A.

[0024] Fig. 2 is a plan view of the battery unit 5. Note that the cover member 30 is omitted from Fig. 2. The case body 25 of the battery housing case 10 includes a pair of skeletal members 11 extending substantially along the longitudinal direction of the vehicle body. The pair of skeletal members 11 are spaced apart in the vehicle width direction. The pair of skeletal members 11 are connected by a first cross member 12f, a second cross member 12s, and a third cross member 12t that extend along the vehicle width direction. Both ends of the first cross member 12f in the extension direction are connected to the vicinity of the front ends of the left and right skeletal members 11, and both ends of the second cross member 12s in the extension direction are connected to the vicinity of the rear ends of the left and right skeletal members 11. Furthermore, both ends of the third cross member 12t in the extension direction are connected to approximately the center of the left and right skeletal members 11 in the longitudinal direction.

[0025] In this embodiment, the vehicle body longitudinal direction is the first direction substantially perpendicular to the vertical direction, and the vehicle width direction is the second direction substantially perpendicular to the vertical direction and the first direction. The pair of skeletal members 11 extend along the first direction (vehicle body longitudinal direction) and are spaced apart from each other in the second direction (vehicle width direction). The first, second, and third cross members 12f, 12s, and 12t extend along the second direction (vehicle width direction) and form cross members whose both ends in the extension direction are connected to the pair of skeletal members 11.

[0026] The case body 25 further includes a bottom wall member 13 that covers the lower space between the pair of skeletal members 11. The bottom wall member 13 is rectangular in plan view, and the pair of skeletal members 11 and the lower ends of the first, second, and third cross members 12f, 12s, and 12t are coupled to its upper surface. A plurality (four) of battery modules 7 are mounted on the upper surface of the bottom wall member 13. Two battery modules 7 are mounted side by side in the vehicle width direction on the front upper surface of the bottom wall member 13, sandwiching the third cross member 12t therebetween, and the remaining two battery modules 7 are similarly mounted side by side in the vehicle width direction on the rear upper surface of the bottom wall member 13, sandwiching the third cross member 12t therebetween. The battery modules 7 (plurality of battery cells 6) housed in the case body 25 are surrounded on the outside by the pair of skeletal members 11 and the first, second, and third cross members 12f, 12s, and 12t. The number of battery modules 7 housed in the battery housing case 10 is not limited to four, and any number can be selected depending on the size of the battery housing case 10, the layout of the mounted components, etc.

[0027] 2, an equipment mounting frame 33 is installed on top of the first cross member 12f and the second cross member 12s of the battery housing case 10. The equipment mounting frame 33 is installed in the center of the first cross member 12f and the second cross member 12s in the vehicle width direction so as to straddle the front and rear above the center region of the four battery modules 7 in the vehicle width direction. Control equipment and its wiring (not shown) are mounted on the top of the equipment mounting frame 33.

[0028] The bottom wall member 13 includes a base wall 8b facing the storage area for the battery modules 7 and a flow path forming wall 8f joined to the underside of the base wall 8b. The flow path forming wall 8f forms a coolant passage 14 between itself and the underside of the base wall 8b for flowing coolant inside. The multiple battery modules 7 stored in the battery storage case 10 are cooled by the coolant flowing through the coolant passage 14. The bottom wall member 13 has a multi-wall structure with a hollow portion inside, formed by the base wall 8b and the flow path forming wall 8f below it. This multi-wall structure maintains the bottom wall member 13's high rigidity.

[0029] Each battery module 7 houses a plurality of battery cells 6 in a rectangular parallelepiped module case 40 with a narrow vertical width. The plurality of battery cells 6 are stacked in the module case 40 along the vehicle width direction. A predetermined number of battery cells 6 are grouped together to form a battery module 7 and housed in a battery housing case 10. The module case 40 includes a case main body 41 that opens upward and houses a plurality of battery cells 6 therein, and a cover wall 42 that is attached to the top surface of the case main body 41 and closes the opening of the case main body 41. When attached to the case main body 41, the cover wall 42 covers the upper parts of the plurality of battery cells 6 inside the case main body 41. The case main body 41 and cover wall 42 that form the module case 40 are formed from a highly rigid metal plate or the like. A separation space S is secured between each battery module 7 housed in the battery housing case 10 and the adjacent frame member 11 so that the battery modules 7 are not in contact with the frame member 11 in the vehicle width direction.

[0030] As shown in Figure 1, the skeleton member 11 has a hollow base frame portion 15 on its inner surface in the vehicle width direction to which the extending ends of the first, second, and third cross members 12f, 12s, and 12t are connected, and a hollow mounting frame portion 16 extending outward in the vehicle width direction from the outer end of the base frame portion 15 in the vehicle width direction. The base frame portion 15 has a cross section perpendicular to the longitudinal direction of the vehicle body, the cross section being a vertically long, rectangular closed cross section that extends substantially along the longitudinal direction of the vehicle body.

[0031] The mounting frame portion 16 has an upper wall portion 17 whose inner end in the vehicle width direction is connected to approximately the center in the height direction of the base frame portion 15, and a lower wall portion 18 whose inner end in the vehicle width direction is connected to the lower end of the base frame portion 15. The lower wall portion 18 is disposed at a height position approximately equal to that of the bottom wall member 13. The outer ends in the vehicle width direction of the upper wall portion 17 and the lower wall portion 18 are closed by end walls 29 that stand up approximately vertically. The mounting frame 16 has a horizontally elongated, substantially rectangular closed cross section formed by the outer side wall of the base frame 15 in the vehicle width direction, the upper wall 17, the lower wall 18, and an end wall 29. This closed cross section extends in the fore-and-aft direction of the vehicle body. The closed cross section of the mounting frame 16 is reinforced by reinforcing ribs 27 and 28.

[0032] Fig. 3 is a plan view of the battery unit 5, showing an enlarged portion of Fig. 2. Fig. 4 is an enlarged view of part IV of Fig. 3. The third cross member 12t, located at the center of the battery housing 10 in the longitudinal direction, includes a lower member 12tL, both ends of which in the extension direction are welded to the base frame portions 15 of the left and right skeletal members 11, and an upper member 12tU, which is placed on top of the lower member 12tL and fixed to the lower member 12tL in this state with fastening members 35. The upper member 12tU has a length extending in the vehicle width direction that is slightly shorter than that of the lower member 12tL. Widened portions 45 are formed at both ends of the lower member 12tL in the vehicle width direction, and the width of the widened portions 45 gradually increases in the longitudinal direction toward fixed portions 44 (welded fixed portions) to the skeletal members 11. Both ends of the upper member 12tU in the vehicle width direction are joined by fastening members 35 to the narrowest portions of the widened portions 45 of the lower members 12tL.

[0033] As shown in FIG. 3 , the upper surface of the upper member 12tU is provided with a multi-rib structure 51 in which a rib 50 branches into two (plural) ribs from one end to the other in the vehicle width direction (second direction) before rejoining, and an individual rib 52 that extends along the vehicle width direction (second direction) and whose end in the extending direction is connected to the end (the single rib 50) of the multi-rib structure 51 in the vehicle width direction. The multi-rib structure 51 and the individual rib 52 are alternately arranged along the vehicle width direction on the upper surface of the upper member 12tU (third cross member 12t). The multi-rib structure 51 is disposed at each end of the upper member 12tU (third cross member 12t) in the vehicle width direction. The two ribs 50 branching from each multi-rib structure 51 extend along the vehicle width direction so as to be parallel to each other. Additionally, the multiple rib structure portions 51 at both ends in the vehicle width direction are joined to the widened portion 45 on the lower member 12tL side at the portion where the two ribs 50 join together.

[0034] FIG. 5 is an enlarged plan view of a portion of third cross member 12t corresponding to portion V in FIG. In each of the multiple rib structures 51 of the upper member 12tU, near a portion where the number of ribs 50 changes from two (plural) to one, a pair of reinforcing ribs 53 extending parallel to the front side along the longitudinal direction and a pair of reinforcing ribs 53 extending parallel to the rear side along the longitudinal direction are integrally formed. Each pair of reinforcing ribs 53 is disposed at a predetermined distance apart in the vehicle width direction. Furthermore, a fastening boss 54 is provided adjacent to the end of each pair of reinforcing ribs 53 in the extending direction, to which an edge of the cover wall 42 of the battery module 7 is fastened and fixed. Each fastening boss 54 is formed with an insertion hole 56 into which a shaft portion of a fastening member 55 (see FIG. 3) is inserted.

[0035] On the other hand, the battery module 7 disposed on the rear side of the third cross member 12t has fastening tongues 60 extending from the front edge of its cover wall 42, which are superimposed on the upper surfaces of the fastening bosses 54 at the rear edge of the third cross member 12t, as shown in Fig. 3. Each fastening tongue 60 at the front edge of the cover wall 42 is fastened and fixed to the corresponding fastening boss 54 with fastening members 55 while superimposed on the upper surface of the corresponding fastening boss 54.

[0036] Similarly, the battery module 7 disposed on the front side of the third cross member 12t has fastening tongues 60 extending from the rear edge of its cover wall 42. The fastening tongues 60 are placed on the upper surfaces of the corresponding fastening bosses 54 at the front edge of the third cross member 12t. Each fastening tongue 60 at the rear edge of this front cover wall 42 is placed on the upper surface of the corresponding fastening boss 54 and is fastened to the fastening boss 54 with fastening members 55 in this state.

[0037] 3, a plurality of fastening bosses 65 are provided protruding forward from the front edge of the rear second cross member 12s. The battery module 7 disposed in front of the second cross member 12s has fastening tongues 67 extending from the rear edge of its cover wall 42. Each fastening tongue 67 on the rear edge of the rear cover wall 42 is fastened and fixed to the corresponding fastening boss 65 with fastening members 55 while overlapping the upper surface of the corresponding fastening boss 65.

[0038] Here, the fastening boss portion 54 (connection portion to the cover wall 42) of the central third cross member 12t and the fastening boss portion 65 (connection portion to the cover wall 42) of the rear second cross member 12s are positioned at positions offset from each other in the vehicle width direction. In other words, the connection portion between the third cross member 12t on the leading edge side of the cover wall 42 and the connection portion between the second cross member 12s on the trailing edge side of the cover wall 42 are all positioned at positions offset from each other in the vehicle width direction.

[0039] 3 does not show the connection portion between the first cross member 12f and the front cover wall 42, but the connection portion between the first cross member 12f and the front cover wall 42 has a similar structure to the connection portion between the second cross member 12s and the rear cover wall 42. The connection portion between the rear edge of the front cover wall 42 and the third cross member 12t and the connection portion between the front edge of the front cover wall 42 and the first cross member 12f are all positioned at positions offset in the vehicle width direction.

[0040] As described above, in the battery unit 5 of this embodiment, the front and rear end edges of the cover wall 42 of the battery module 7 are connected to two adjacent cross members (the third cross member 12t and the second cross member 12s, and the third cross member 12t and the first cross member 12f). Therefore, when an impact load is input to one of the frame members 11 from one side in the vehicle width direction, the impact load transmitted to one of the adjacent cross members is efficiently transmitted to the other cross member through the cover wall 42. As a result, the input impact load is efficiently distributed and supported by the multiple cross members through the cover wall 42.

[0041] Furthermore, in the battery unit 5 of this embodiment, one of the adjacent cross members (the third cross member 12t) has a multi-rib structure 51 and a single rib 52 interconnected in the vehicle width direction, and the longitudinal edge of the cover wall 42 is connected to the multi-rib structure 51 near a portion where the number of ribs 50 in the multi-rib structure 51 changes from two to one. Therefore, an impact load transmitted to the multi-rib structure 51 of the third cross member 12t is transmitted to the cover wall 42 through a portion that is relatively susceptible to movement in the outward opening direction in response to the input load. As a result, an impact load input to the third cross member 12t is efficiently transmitted through the cover wall 42 to the first cross member 12f and the second cross member 12s. Therefore, when the battery unit 5 of this embodiment is employed, it is possible to efficiently absorb the input impact load using the cover wall 42 without increasing the number of cross members or the size of the cross members. Thus, it is possible to efficiently absorb the input impact load by portions other than the battery cells 6 while avoiding an increase in the size and weight of the battery housing case 10.

[0042] Furthermore, in the battery unit 5 of this embodiment, the third cross member 12t, which has a multi-rib structure 51 and an individual rib 52, includes a widened portion 45 whose front-to-rear width gradually increases toward the fastening portion 44 with the skeletal member 11. Therefore, an impact load input to one of the skeletal members 11 from one side in the vehicle width direction is transmitted from the fastening portion 44 with the skeletal member 11 of the third cross member 12t through the widened portion 45 to the multi-rib structure 51 and the individual rib 52. Since the widened portion 45 gradually decreases in front-to-rear width from the fastening portion 44 with the skeletal member 11 toward the multi-rib structure 51 and the individual rib 52, the load input from the skeletal member 11 to the third cross member 12t is more easily transmitted to the multi-rib structure 51 and the individual rib 52. As a result, the impact load input to the third cross member 12t is more easily transmitted by the first cross member 12f and the second cross member 12s via the cover wall 42. Additionally, an impact load input from one side of the third cross member 12t is transmitted to the other skeletal member 11 through the widened portion 45 on the other side of the third cross member 12t. At this time, the widened portion 45 on the other side gradually increases in front-to-rear width toward the fixed portion 44 with the other skeletal member 11, so the impact load is stably received by a wide area of ​​the other skeletal member 11 in the front-to-rear direction. Therefore, when the battery unit 5 of this embodiment is employed, it becomes possible to more efficiently receive the input impact load by portions other than the battery cells.

[0043] Furthermore, in the battery unit 5 of this embodiment, a fastening boss 54 is provided via a pair of reinforcing ribs 53 extending in the front-to-rear direction near the location where the number of ribs 50 in the multi-rib structure 51 of the third cross member 12t changes from two to one. Therefore, an impact load input to the multi-rib structure 51 of the third cross member 12t can be efficiently transmitted to the cover wall 42 via the pair of reinforcing ribs 53.

[0044] Furthermore, in the battery unit 5 of this embodiment, a separation space S is provided between the skeletal member 11 and the adjacent battery module 7, separating them in the vehicle width direction. When an impact load is input to one of the skeletal members 11 from one side in the vehicle width direction, the impact load is received by the multiple cross members and the cover wall 42 of the battery module 7. At this time, even if a portion of one of the skeletal members 11 is displaced inward in the vehicle width direction, the separation space S is provided between the skeletal member 11 and the battery module 7, making it difficult for the load to be transmitted directly from the skeletal member 11 to the battery module 7. Therefore, when the battery unit 5 of this embodiment is employed, it is possible to more effectively protect the battery cells 6 when an impact load is input.

[0045] Furthermore, in the battery unit 5 of this embodiment, two adjacent cross members (the third cross member 12t and the second cross member 12s, and the third cross member 12t and the first cross member 12f) are connected to the edge of the cover wall by fastening bosses 54, 65 that are positioned at positions offset from each other in the vehicle width direction. Therefore, when an impact load is applied to one of the frame members from one side in the vehicle width direction, the load is absorbed by the two adjacent cross members and also by the cover wall 42. In this case, the fastening bosses 54, 65, which are the points at which the load is transmitted from the two cross members to the cover wall 42, are positioned at positions offset from each other in the vehicle width direction. Therefore, when the battery unit 5 of this embodiment is used, the cover wall 42 is less likely to bend or deform when an impact load is applied, and the cover wall 42 can efficiently absorb the impact load.

[0046] The present invention is not limited to the above-described embodiment, and various design modifications are possible without departing from the spirit of the present invention. In the above-described embodiment, three cross members are provided spaced apart in the front-rear direction and connected to a pair of frame members 11, but the number of cross members is not limited to three. The number of cross members may be four or more or two or less.

[0047] In the above embodiment, the pair of skeletal members 11 extend along the vehicle width direction and are spaced apart from each other in the vehicle width direction, and the first, second, and third cross members 12f, 12s, and 12t are arranged along the vehicle width direction. However, the arrangement of the skeletal members and cross members is not limited to this. For example, the pair of skeletal members may extend along the vehicle width direction and be spaced apart from each other in the vehicle width direction, and the cross members may be arranged along the vehicle width direction.

[0048] Furthermore, in the above embodiment, the multiple rib structure portion 51 and the individual rib portion 52 are provided on only one of the adjacent cross members, but the multiple rib structure portion 51 and the individual rib portion 52 may also be provided on both of the adjacent cross members in the same manner.

[0049] Furthermore, the multi-rib structure portion 51 in the above embodiment has a shape in which one rib 50 branches into two from one side of the extension direction to the other side and then merges into one again, but the multi-rib structure portion 51 may also have a shape in which one rib 50 branches into three or more from one side of the extension direction to the other side and then merges into one again. [Explanation of symbols]

[0050] 3...Side sill (framework) 5...Battery unit 6...Battery cell 7...Battery module 10...Battery storage case 11...skeletal member 12f...First cross member (cross member) 12s...Second cross member (cross member) 12t...3rd cross member (cross member) 40...Module case 42...Cover wall 44…Fixed part 45...Wide section 50...Ribs 51...Multiple rib structure 52...Single rib section 53...Reinforcing rib 54...Fastening boss (connecting part) 65...Fastening boss (connecting part) S: Separate space

Claims

1. a battery module in which battery cells are housed in a module case; a battery housing case attached to a frame member of a vehicle and housing the battery module therein; The battery housing case includes: a pair of skeletal members extending along a first direction substantially perpendicular to the vertical direction; a plurality of cross members extending along a vertical direction and a second direction substantially perpendicular to the first direction, and both ends in the extending direction being connected to the pair of framework members; the module case includes a cover wall that covers an upper portion of the battery cell and has opposite end edges in the first direction that are respectively connected to the two adjacent cross members; At least one of the adjacent cross members is a multi-rib structure portion in which a rib branches from one end side to the other end side in the second direction and then merges into a single rib again; a single rib portion extending along the second direction and having an end portion in the extending direction connected to the multi-rib structure portion, A battery unit for a vehicle, characterized in that the edge of the cover wall is connected to the vicinity of the portion of the multi-rib structure where the number of ribs changes from multiple to one.

2. The vehicle battery unit described in claim 1, characterized in that the cross member having the multiple rib structure portion and the single rib portion has an expanded portion in which the width in the first direction gradually increases in a fan-out manner toward the fixed portion with the skeletal member.

3. A battery unit for a vehicle as described in claim 1, characterized in that a connection portion to the cover wall is provided near the portion where the number of ribs of the multi-rib structure portion of the cross member changes from multiple to one via multiple reinforcing ribs extending along the first direction.

4. The battery unit for a vehicle according to claim 2 , wherein a separation space is provided between the framework member and the battery module, the separation space being spaced apart in the second direction.

5. 2. The battery unit for a vehicle according to claim 1, wherein the connecting portions of the two adjacent cross members to the cover wall are provided at positions offset from each other in the second direction.

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