VEHICLE UNDERSTRUCTURE

Abstract

Vehicle underbody structure (10) comprising: a main body housing section (34) arranged on the underside of a vehicle cabin floor, comprising a bottom wall (40) and a front wall (42) formed on the front of the main body housing section, a rear wall (44), a left wall (46) and a right wall (48) extending towards the top of the vehicle from a circumferential edge section of the bottom wall (40), the main body housing section (34) accommodating a battery (50) inside; a front section extension section (36) formed as a rectangular box in plan view with a front wall (64), a left wall (66) and a right wall (68) and formed integrally with the front wall (42) of the main body housing section (34) on the front of the main body housing section (34);and a shock absorber section (84, 86) extending in a longitudinal direction of the vehicle, wherein a rear end section of the shock absorber section (84, 86) is connected to the front wall (64) of the front section extension section (36) in a vehicle-front area of ​​the front section extension section (36), wherein the shock absorber section (84, 86) deforms as a result of the application of an impact load to the front of the vehicle.

Description

BACKGROUNDTechnical FieldThe present disclosure relates to a vehicle lower structure.Related ArtIn a battery-carrying vehicle such as an electric car or the like, a plurality of batteries are mounted below the vehicle cabin floor in a state of being accommodated in a battery case. Consequently, there is a large load (mass) portion below the vehicle cabin. In a case where the vehicle is involved in a frontal collision with an obstacle or the like, a large inertial force may be applied to the battery unit and the vehicle cabin disposed above, and the vehicle cabin may easily deform.Accordingly, various proposals have been made to reduce the impact force applied to the vehicle cabin in such a battery-carrying vehicle. For example, JP 2012-201 284 A discloses a shock absorbing floor structure in which a frame that is substantially U-shaped in cross section and long in the longitudinal direction extends below the floor in an electric car to a region closer to the vehicle front than the front wheels of the vehicle. Further, a structure is proposed in which, because the battery is not accommodated in a fixed area of this frame from the distal end (the front end), this portion is made as a shock absorbing portion at the time of a frontal collision.Further, JP 2012-091 636 A describes, in an electric car in which the battery unit is mounted on the lower portion of the vehicle cabin floor, a battery mounting structure in which the front end portions of frame members extending in the vehicle front-rear direction and forming support members that support the battery module of the battery unit are joined to the suspension cross member. By forming such a structure, the shock absorption performance can be improved by transmitting the inertial force, which is a result of the battery unit at the time of a frontal collision, from the connection portions to the suspension member. However, in the impact absorbing floor structure of JP 2012-201 284 A, a frame continuous in a single straight line in the vehicle front-rear direction is formed. Consequently, it is conceivable that it is difficult to sufficiently secure the shock absorption performance of the frame, and there is a concern that the battery (the battery cells) itself may be damaged.Further, in the battery mounting structure of JP 2012-091 636 A, a structure that receives the inertial force needs to be separately provided on the suspension member in order for the suspension member to be able to receive the inertial force exerted from the battery module at the time of a frontal collision.DE 10 2013 204 765 A1 discloses a box-shaped battery housing in which the side sections are deformable in the event of a side impact. JP 2006-182 295 A shows a vehicle frame which consists of a rectangular frame which has front and rear longitudinal beams. The battery is attached to a separate plate which closes the rectangular frame from below. The battery box is closed from above by a further plate. FR 1 011 256 A shows a vehicle frame which accommodates batteries in a battery compartment in the middle of the vehicle. The frame has two longitudinal members to which the front axle is attached. DE 10 2016 119 670 B4 shows a vehicle frame in which a central battery compartment is arranged between two longitudinal supports. On a front wall of the battery compartment, two forwardly extending side rails are mounted. The front end of these two side rails is connected to a bumper structure.SUMMARYThe present disclosure provides, in a vehicle in which a battery is accommodated below a floor, a vehicle lower structure that can improve shock absorption performance by a simple structure.A first aspect of the present invention is a vehicle lower structure according to claim 1, more specifically comprising: a case main body portion disposed at a vehicle lower side of a vehicle cabin floor and having a bottom wall and peripheral walls extending toward the vehicle upper side from a peripheral edge portion of the bottom wall, the case main body portion accommodating a battery in an interior thereof; a front portion extending portion formed integrally with the case main body portion at a vehicle front side of the case main body portion, at the peripheral wall that is at a vehicle front side of the case main body portion; and a shock absorber portion extending in a vehicle front-rear direction, a rear end portion of the shock absorber portion being connected to a vehicle front side region of the front portion extension portion, the shock absorber portion deforming due to application of the collision load from a vehicle front side.In the vehicle lower structure according to the first aspect, the case main body portion having the bottom wall and the peripheral wall is disposed at the vehicle lower side of the vehicle cabin floor, and a battery is accommodated in the interior thereof. Further, the front portion extending portion on the vehicle front side of the case main body portion is formed integrally with the case main body portion from the peripheral wall on the vehicle front side of the case main body portion. The vehicle lower structure has, on the vehicle front side of this front portion extension portion, the shock absorbing portion which extends in the vehicle front-rear direction and whose rear end portion is connected to the vehicle front side of the front portion extension portion.Consequently, in a case where the vehicle is involved in a frontal impact, the collision load is first applied to the shock absorbing portion. As a result, the shock absorbing portion deforms and shock energy is absorbed. In a case where the impact energy cannot be fully absorbed by the deformation of the shock absorbing portion, the front portion extending portion deforms and the collision energy by the frontal impact is absorbed. Therefore, the deformation of the case main body portion or the damage of the battery accommodated in the inside of the case main body portion can be prevented or suppressed.Further, since the front portion extending portion is integrally provided with the case main body portion, the structure can be simple (the assemblability becomes good).In a second aspect of the present disclosure, in the above-described first aspect, the case main body portion may be connected to rocker arms, the rocker arms extending in the vehicle front-rear direction at both sides of the case main body portion in the vehicle width direction.In a second aspect of the present disclosure, the case main body portion is connected to the pair of rocker arms extending in the vehicle front-rear direction at both end portions of the case main body portion in the vehicle width direction. Consequently, the collision load applied to the case main body accommodating the battery due to a front collision of the vehicle is dispersed to the rocker panels. Consequently, deformation of the case main body portion or damage of the battery accommodated in the inside of the case main body portion can be further suppressed or prevented.In a third aspect of the present disclosure, in the above-described aspects, a pair of left and right suspension legs may be pivotally mounted to both end portions of the front portion extension portion in the vehicle width direction.In the vehicle lower structure according to the third aspect of the present invention, a pair of left and right suspension axles are mounted on the vehicle transverse direction both end portions of the front portion extension portion. Consequently, existing suspension members supporting the front wheel suspensions become unnecessary, and the vehicle body structure can be simplified. Further, the front wheel suspensions (the suspension axles) can be made integral with and a module with the front portion extension portion (the case main body portion).In a frontal impact of the vehicle, collision energy is absorbed by the front portion extension portion deforming and the front wheel suspensions mounted on the front portion extension portion also deforming. As a result, the absorbed amount of collision energy on the front side of the case main body portion can be increased, and deformation of the case main body portion or damage of the battery accommodated inside the case main body portion can be further prevented or suppressed.In a fourth aspect of the present disclosure, in the above-described aspects, the shock absorber portion may include a pair of left and right sub-members extending in the vehicle front-rear direction and having a sub-reinforcement connecting the front ends of the sub-members.In the vehicle lower structure according to the fourth aspect of the present invention, the shock absorbing portion disposed at the vehicle front side of the front portion extending portion includes a pair of left and right sub-members extending in the vehicle front-rear direction and a sub-reinforcement connecting the front ends of the sub-members. Consequently, the collision energy at the time of a frontal impact can be absorbed by the under reinforce and the sub-members deforming upon a frontal impact of the vehicle.According to the above-described aspects, the vehicle lower structure of the present disclosure can improve the shock absorption performance at the time of a front collision of a vehicle with a simple structure.BRIEF DESCRIPTION OF THE DRAWINGSAn exemplary embodiment will be described in detail on the basis of the following figures, wherein: FIG. 1 is a schematic drawing showing a vehicle lower structure according to an embodiment of the present disclosure as viewed from a vehicle side portion; FIG. 2 is a perspective view showing the vehicle lower structure according to the embodiment of the present disclosure, a portion of which is omitted; and FIG. 3 is a sectional view taken along line A-A of FIG. 1.DETAILED DESCRIPTIONA vehicle lower structure according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 3. Note that the vehicle upper side in the vertical direction is indicated by an arrow UP, the vehicle front-rear direction side is indicated by an arrow FRONT, and the vehicle transverse direction right side is indicated by an arrow RIGHT. Furthermore, the illustration of the side elements 14 and sills 122 is omitted in FIG. 2.A vehicle 12 to which a vehicle lower structure 10 is applied will be described first.As shown in FIG. 1, the vehicle 12 is an electric car and has the side members 14 that are vehicle frame members and a battery pack 16 that is supported on the side members 14.As shown in FIG. 1, the side members 14 (only one of which is shown) are a pair of left and right vehicle frame members that extend from the front end to the rear end of the vehicle at the vehicle transverse direction both side portions of the vehicle. Each of the side members 14 includes a front side member 18, an under-floor reinforcement 20, and a rear side member 22. The underbody reinforcement 20 extends from the rear end of the front side member 18 in continuation with the vehicle rear side thereof to a position one step lower than the front side member 18 and supports a floor panel 120. The rear side member 22 extends from the rear end of the underbody reinforcement 20 in continuation with the vehicle rear side thereof to a position one step higher than the underbody reinforcement 20.An upper reinforcement 26 is mounted to the front ends of the front side members 18 via crash boxes 24. The upper reinforcement 26 extends in the vehicle width direction and connects the front ends of the pair of front side members 18 (the crash boxes 24).The rear end of the rear member 22 is similarly connected to the other rear member 22 by a reinforcement 28.As shown in FIG. 2, the battery pack 16 has a case lower 30, a case upper 32 which is a cover body of a battery module accommodating portion of the case lower 30.The case lower 30 includes a case main body portion 34, a front portion extending portion 36, and a rear portion extending portion 38. The front portion extending portion 36 is formed at the front side of the case main body portion 34, and is shaped as a box which is rectangular in plan view and whose upper portion is open. The rear extension portion 38 is formed at the rear of the case main body portion 34, and is shaped as a box that is rectangular in plan view and whose upper portion is open. In the case lower 30, the case main body portion 34, the front portion extending portion 36, and the rear portion extending portion 38 are integrally formed as a molding.The case main body portion 34 is formed rectangular in plan view by surrounding a bottom wall 40 with a front wall 42, a rear wall 44, a left wall 46, and a right wall 48. A battery module 50 is accommodated inside this case main body portion 34.Screw holes 52 for mounting the upper case 32 are formed in the top surfaces of the front wall 42, the rear wall 44, the left wall 46, and the right wall 48 of the case main body portion 34. Note that, in FIG. 2, only one of the screw holes 52 is denoted by the reference numeral, and the other reference numerals are omitted to avoid obscuring the drawing.Further, a plurality of mounting portions 54 that are for mounting the case main body portion 34 to the underbody reinforcement 20 are formed on the outer side surfaces of the left wall 46 and the right wall 48 at predetermined intervals in the vehicle front-rear direction. As shown in FIGS. 1 and 2, the mounting portion 54 has a top wall 56 that is rectangular as viewed in plan view and a pair of side walls 58 that extend downward from the front end and the rear end of the top wall 56, respectively. As shown in FIGS. 2 and 3, the side walls 58 are shaped such that the width in the vertical direction is wide on the left wall 46 side and on the right wall 48 side thereof, and the width in the vertical directions becomes narrower toward the vehicle width direction outer sides.A through hole 60 for passing a fastener is formed in the top wall 56. Note that, in FIGS. 1 and 2, only one of the through holes 60 is denoted by the reference numeral, and the reference numerals are omitted from the others to avoid obscuring the drawing.The front portion extending portion 36 is formed integrally with the case main body portion 34 on the vehicle front side of the case main body portion 34 (the front wall 42). The front portion extending portion 36 is formed to be rectangular in plan view by surrounding a bottom wall 62 by a front wall 64, a left wall 66, a right wall 68, and the front wall 42 of the case main body portion 34. Note that no battery module is disposed inside this front portion extension portion 36.Further, as shown in FIG. 2, the vehicle width direction width of the front portion extension portion 36 is set to be narrow as compared with the vehicle width direction width of the case main body portion 34 to be able to mount steering knuckle 80A, 80B.Further, brackets 70A, 70B for mounting front side members 18 are provided at the front end portions of the top surfaces of the left wall 66 and the right wall 68, respectively. The boom 70A has a leg portion 72A that extends upward inclined toward a vehicle width direction outer side (upward and leftward) from the top surface of the left wall 66, and a mounting portion 74A that is configured to extend toward the vehicle width direction outer side (the left side) from the upper end of the leg portion 72A. A fastener passing hole 76A for fastening the front side member 18 is formed in the mounting portion 74A. Thus, as shown in FIG. 1, the mounting portion 74A is made to abut on the bottom surface of the front side member 18, and the bracket 70A is fixed to the front side member 18 by a fixing member (not shown) passing through the passing hole 76A. That is, the front portion extending portion 36 is fixed to the front side member 18.The boom 70B has left-right symmetry with respect to the boom 70A. Thus, the constituent elements of the boom 70B that are the same as the constituent elements of the boom 70A are denoted by the same reference numerals as the constituent elements of the boom 70A except that a B replaces the A and the detailed description thereof is omitted.The knuckle 80A is supported at the lower portion of the left wall 66 to pivot in the vertical direction about a shaft body extending in the vehicle front-rear direction and supported at the left wall 66. The knuckle 80B is likewise supported on the lower portion of the right wall 68. Thus, the front portion extending portion 36 is made integral with the front suspensions including the steering knuckles 80A, 80B.As shown in FIGS. 1 and 2, a steering gear 82 extending in the vehicle width direction is mounted on the upper portion of the front wall 64.Rear ends of a pair of left and right sub-members 84 are connected to the lower portion of the front wall 64.The respective sub-members 84 extend in the vehicle front-rear direction on the vehicle front side of the front portion extension portion 36, and the front ends thereof are connected by a sub-reinforcement 86 extending in the vehicle width direction. Note that the sub-members 84 and the sub-reinforcement 86 are structured to deform more easily than the front portion extension portion 36 when a collision load is input from the vehicle front.As shown in FIG. 2, the rear portion extension portion 38 is integrally formed with the case main body portion 34 on the vehicle rear side of the case main body portion 34 (the rear wall 44). The rear portion extension portion 38 is formed rectangular in a plan view by surrounding a bottom wall 88 by a left wall 90, a right wall 92, a rear wall 94, and the rear wall 44 of the case main body portion 34. Note that no battery module is disposed inside this rear portion extension portion 38.Further, as shown in FIG. 2, the width of the rear portion extension portion 38 in the vehicle width direction is formed to be narrow as compared with the width of the case main body portion 34 in the vehicle width direction.Further, brackets 96A, 96B for mounting the rear side members 22 are provided at the rear end portions of the top surfaces of the left wall 90 and the right wall 92, respectively. In the same manner as the beams 70A, 70B, the beams 96A, 96B have leg portions 100A, 100B and mounting portions 102A, 102B in which through holes 104A, 104B are formed. Further, the brackets 96A, 96B are fixed to the rear side members 22 by fastening members inserted into the through holes 104A, 104B. That is, the rear portion extension portion 38 is fixed to the rear side members 22.Further, constituent elements of unillustrated rear suspensions are fixed to the left wall 90 and the right wall 92, and the rear suspensions and the rear portion extension portion 38 are made integral.The upper case 32 is placed on the case main body portion 34 of the lower case 30. The upper case 32 has a cover main body portion 108 formed in the shape of a box that is rectangular in plan view and whose lower side is open, and a flange portion 110 that extends toward the outside from the opening portion of the cover main body portion 108. A plurality of fastener passing holes 112 are formed in the flange portion 110 at positions facing the screw holes 52 when the flange portion 110 is placed on the upper portion of the housing main body portion 34. Thus, the upper case 32 is fixed to the case main body portion 34 by placing the flange portion 110 of the upper case 32 on the upper portion of the case main body portion 34, and passing fastening members through the through holes 112 of the flange portion 110 and screwing with the screw holes 52 of the case main body portion 34.Note that in FIG. 3, the battery pack 16 is disposed below the bottom plate 120. The floor panel 120 is joined to the sills 122 that extend in the vehicle front-rear direction at both vehicle width direction end portions of the vehicle cabin. Note that a closed cross section of the rocker 122 is formed by joining the flange portions of a rocker panel 124 disposed on the vehicle width direction inner side and a rocker panel outer 126 disposed on the vehicle width direction outer side. Further, the floor panel 120 is supported from below by the under-floor reinforcements 20 that are hat-shaped in cross section. In cross section, the underbody reinforcement 20 is formed as a hat whose upper side is open, and a closed cross section is formed by joining flange portions 128 at both end portions of the underbody reinforcement 20 to the floor panel 120. Further, through holes for fastening members (bolts 132) are formed in bottom walls 130 of the underbody reinforcements 20. In assembly, the battery pack 16 (the case main body portion 34) is fixed to the under-floor reinforcements 20 by inserting the bolts through the through-holes 60 of the mounting portions 54 of the case main body portion 34 from the through-hole sides of the bottom walls 130 of the under-floor reinforcements 20 and fastening them by nuts 134 from below. That is, the battery pack 16 (the case main body portion 34) is connected to the sills 122 via the under-floor reinforcements 20 and the floor panel 120.Note that, in FIG. 1, reference numeral 136 denotes an electric motor, and reference numeral 138 denotes an upper monocoque body.The operation of the vehicle lower structure 10 configured as described above will be described.In a case where the vehicle 12 is involved in a frontal impact with an obstacle or the like, firstly, collision load is input to the sub-reinforcement 86 and the sub-members 84 from the vehicle front, and the sub-reinforcement 86 and the sub-members 84 deform. As a result, the collision energy occurring due to the front collision is absorbed. In a case where the collision energy is not completely absorbed by the deformation of the sub reinforcement 86 and the sub members 84, the collision energy is absorbed by deforming the front portion extension portion 36 to which the rear ends of the sub members 84 are connected and constituent members of the front wheel suspensions mounted on the front portion extension portion 36.In this way, at the time of a front collision of the vehicle, by the under reinforce 86, the sub members 84, the front portion extension portion 36, and constituent elements of the front suspension wheels attached to the front portion extension portion 36 deforming, collision energy is sufficiently absorbed, and deformation of the case main body portion 34 and damage to the battery module 50 accommodated in the case main body portion 34 can be prevented or suppressed.Further, in the case of a slight frontal impact, the deformation occurs only at the sub-members 84 and the sub-reinforcement 86. Since the sub-members 84, the sub-reinforcement 86, and the battery pack 16 (the case lower part 30) are formed as separate bodies, it is sufficient to replace only the sub-members 84 and the sub-reinforcement 86 after the collision.In addition, the battery pack 16 (the case main body portion 34 of the case lower 30) is connected to the sills 122 via the under-floor reinforcement 20 and the floor panel 120. Consequently, the collision load applied to the battery pack 16 (the case main body portion 34) is dispersed into the sills 122. Consequently, in a frontal impact of the vehicle, deformation of the case main body portion 34 and damage to the battery module 50 accommodated in the case main body portion 34 can be further prevented or suppressed.Further, as shown in FIG. 3, on the battery pack 16, the case main body portion 34 is disposed between the pair of underbody reinforcements 20, and the width in the vehicle width direction is secured to be wide. Thus, a battery module 50 of a predetermined capacity can be accommodated inside the case main body portion 34.On the other hand, the width in the vehicle transverse direction of the front portion extension portion 36 is formed to be narrower than that of the housing main body portion 34. Moreover, because the rear portion extension portion 38 is formed the same as the front portion extension portion 36, structural members of the rear suspension may be fixed to the left wall 90 and the right wall 92.Because the front portion extending portion 36 supports the front wheel suspensions (the steering knuckles 80A, 80B) in this manner, existing suspension members can be omitted. Specifically, the front portion extending portion 36 provided on the battery pack 16 to absorb the collision energy at the time of a frontal impact supports the front wheel suspensions (also functions as suspension members). Consequently, the structure of the vehicle body can be simplified. The same applies to the rear portion extension portion 38 equally.Further, the front wheel suspensions and the rear wheel suspensions may be made integral and made a module with the battery pack 16 through the front portion extension portion 36 and the rear portion extension portion 38. Thus, the vehicle is formed by mounting the upper monocoque body 138 on the upper portion of a structure in which the battery pack 16 and the front wheel suspensions and the rear wheel suspensions have been made integral (one module). Consequently, vehicles of various types of vehicles can be manufactured by replacing only the upper monocoque body 138 with an upper monocoque body of a different configuration.Similarly to the case main body portion 34, the battery module 50 and the like are not accommodated inside the front portion extending portion 36. Thus, the front portion extension portion 36 can easily deform in a frontal collision, as compared with a case main body portion 34 inside which the battery module 50 is accommodated.Although the front portion extending portion 36 and the case main body portion 34 are integrally formed, they are separated by the front wall 42, and thereby deformation of the front portion extending portion 36 can be prevented from reaching the case main body portion 34. Consequently, deformation of the case main body portion 34 in a frontal impact and damage of the battery module 50 accommodated in the case main body portion 34 can be prevented or further suppressed.Note that, in the present embodiment, the front portion extension portion 36 is formed in the shape of a box that is rectangular as viewed in plan and whose upper portion is open. However, the present invention is not limited thereto. The shape may be any shape as long as the front portion extension portion has a structure that deforms more easily than the case main body portion 34 and is harder to deform than the sub reinforcement 86 and the sub members 84 in a frontal impact.Further, although the sub reinforcement 86 and the sub members 84 are provided as the shock absorbing portions in the present embodiment, the present disclosure is not limited thereto. The shock absorbing portions may have any configuration as long as they are disposed on the vehicle front side of the front portion extending portion 36 and more easily deform than the front portion extending portion 36 in a frontal impact.In addition, in the present embodiment, the vehicle lower structure 10 is applied to a vehicle 12 that is an electric car, but the present disclosure is not limited thereto. The vehicle lower structure 10 may be applied to a vehicle such as a hybrid vehicle (an HV) or the like, provided that the vehicle is a vehicle in which the battery pack 16 is mounted below the floor panel 120.

Claims

A vehicle lower structure (10) comprising: a case main body portion (34) disposed at a vehicle lower side of a vehicle cabin floor and having a bottom wall (40) and a front wall (42) formed on the vehicle front side of the case main body portion, a rear wall (44), a left wall (46), and a right wall (48) extending toward a vehicle upper side from a peripheral edge portion of the bottom wall (40), the case main body portion (34) accommodating a battery (50) inside thereof; a front portion extension portion (36) shaped as a rectangular box in plan view having a front wall (64), a left wall (66), and a right wall (68) and formed integrally with the front wall (42) of the case main body portion (34) on the vehicle front side of the case main body portion (34); and a shock absorber portion (84, 86) extending in a vehicle front-rear direction, wherein a rear end portion of the shock absorber portion (84, 86) is connected to the front wall (64) of the front portion extension portion (36) in a vehicle front side region of the front portion extension portion (36), the shock absorber portion (84, 86) deforming due to application of shock load to a vehicle front side.The vehicle lower structure (10) according to claim 1, wherein the case main body portion (34) is connected to sills (122), the sills (122) extending in the vehicle front-rear direction at both sides of the case main body portion (34) in the vehicle width direction.The vehicle lower structure (10) according to claim 1 or 2, wherein a pair of left and right suspension legs (80A, 80B) are pivotally mounted to both vehicle width direction end portions of the front portion extension portion (36).The vehicle lower structure (10) according to any one of claims 1 to 3, wherein the shock absorbing portion (84, 86) includes a pair of left and right sub-members (84) extending in the vehicle front-rear direction and including a sub-reinforcement (86) connecting front ends of the sub-members (84).

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