Vehicle body lower structure

The vehicle body lower structure disclosed herein may include: a hollow rocker arranged at a lower lateral part of a vehicle body and extending along a front-rear direction of the vehicle body; a reinforcement member arranged in the rocker; a power source arranged adjacent to the rocker; and an energy absorbing member (an EA member) arranged under the rocker and connected to the power source. A bolt may fix both of the EA member and the reinforcement member to the rocker.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2020-006319 filed on Jan. 17, 2020, the contents of which are hereby incorporated by reference into the present application.

TECHNICAL FIELD

The art disclosed herein relates to a vehicle body lower structure. It relates, in particular, to a vehicle body lower structure in which a power source is arranged adjacent to a rocker.

BACKGROUND

In some electric vehicles, a power source configured to supply power to a traction motor may be arranged adjacent to a rocker. The power source may be a battery, a fuel cell, or the like. The rocker is a frame (a hollow beam) extending along a front-rear direction of the vehicle body at a lower lateral part of the vehicle body. The rocker may also be referred to as “side sill”.

In order to protect the power source from an impact of lateral collision to a lateral part of the vehicle body, a member (energy absorbing member) configured to absorb impact energy caused by the collision may be arranged lateral to the power source. Japanese Patent Application Publication No. 2018-75939 describes an example of such an energy absorbing member. This energy absorbing member extends along a front-rear direction of a vehicle body. The energy absorbing member is arranged adjacent to a power source and under a rocker. The energy absorbing member is connected to a bottom plate of the rocker. Hereafter, an energy absorbing member will be referred to as “EA member” for convenience of description.

A reinforcement member called a bulkhead may be arranged in a rocker in order to enhance strength of the rocker. Japanese Patent Application Publication Nos. 2014-189262 and 2018-193026 describe examples of such a reinforcement member. Japanese Patent Application Publication No. 2014-189262 describes an electric vehicle in which a floor panel is attached between a pair of rockers and a battery pack is attached under the floor panel. A reinforcement member is arranged in each of the rockers. In an electric vehicle described in Japanese Patent Application Publication No. 2018-193026, a reinforcement member serves as an EA member.

SUMMARY

In case of an electric vehicle in which an EA member and a reinforcement member are separately fixed to a rocker, the EA member needs to be fixed to the rocker and the reinforcement member also needs to be fixed to the rocker. Providing the EA member and the reinforcement member separately to the rocker may make a vehicle body lower structure complex. The present disclosure provides a simple vehicle body lower structure in which both of an EA member and a reinforcement member are employed.

A vehicle body lower structure disclosed herein may comprise: a hollow rocker arranged at a lower lateral part of a vehicle body and extending along a front-rear direction of the vehicle body; a reinforcement member arranged in the rocker; a power source arranged adjacent to the rocker; and an energy absorbing member (an EA member) arranged under the rocker and connected to the power source.

In the vehicle body lower structure disclosed herein, a bolt may fix both of the EA member and the reinforcement member to the rocker. A simple structure is achieved because one same bolt fixes both of the EA member and the reinforcement member together to the rocker. The vehicle body lower structure disclosed herein enables a reduced number of required bolts and thus enables reduction in a total weight as compared to a conventional structure in which an EA member and a reinforcement member are fixed to the rocker separately.

In the vehicle body lower structure disclosed herein, a collar may be arranged between the energy absorbing member and the rocker, and the bolt may pass through the collar. Bottom plates of the rocker and the reinforcement member are interposed between the collar and a nut which fixes the bolt. Vibrations of the power source in an up-down direction are transferred to the collar. Deformation of the rocker caused by vibrations of the collar in the up-down direction can be suppressed because two plates (the bottom plates of the rocker and the reinforcement member) are interposed between the collar and the nut which fixes the bolt.

The reinforcement member may be arranged under a center pillar of the vehicle body. The center pillar is one of frames that secure strength of the vehicle body. Especially, the center pillar secures strength against rollover of the vehicle. Strength against rollover can be improved by arranging the reinforcement member under the center pillar.

Details and further developments of the art disclosed herein will be described in DETAILED DESCRIPTION as below.

DETAILED DESCRIPTION

Embodiment

A vehicle body lower structure3according to an embodiment will be described with reference to the drawings.FIG. 1illustrates a perspective view of a vehicle body2. In the coordinate system ofFIG. 1, “Left” indicates “left” when the vehicle body is viewed from the rear toward the front. The “Left” in the coordinate system has the same meaning in all of the drawings.

The vehicle body2comprises a pair of rockers10. The rockers10are arranged respectively at lower lateral parts of the vehicle body2in a vehicle-width (left-right) direction. Each rocker10has an elongated shape and extends along a front-rear direction of the vehicle body2. Lower ends of center pillars51are connected respectively to the rockers10at vicinities of centers of the rockers10in a longitudinal direction of the rockers10. The pair of rockers10and the center pillars51are one type of frame configured to secure rigidity of the vehicle body2. Each of the rockers10is formed by press working operation for a metal plate (typically, a steel plate).

A battery pack40and a floor panel50are arranged between the pair of rockers10. In other words, the battery pack40and the floor panel50are arranged adjacent to each of the rockers10. The battery pack40includes a large number of battery cells therein. The battery cells are connected in series and configured to output high-voltage power. The battery pack40(the plurality of battery cells) is configured to supply the power to an electric traction motor (not shown).

The floor panel50corresponds to a floor of a cabin. Ends of the floor panel50in the vehicle-width direction are fixed respectively to the rockers10. The battery pack40is arranged under the floor panel50. Although details will be described later, energy absorbing members (not shown inFIG. 1) are arranged respectively along the rockers10, and the battery pack40is supported by the pair of rockers10via the energy absorbing members. The battery pack40may be supported by the rockers10via the floor panel50as well as via the energy absorbing members.

The energy absorbing members are arranged on both sides of the battery pack40in the vehicle-width direction. Hereafter, the energy absorbing member(s) will be referred to as EA member(s) for convenience of description.

FIG. 2shows a cross section of the vehicle body2cut along a plane II inFIG. 1.FIG. 2shows a left part of the lower structure3of the vehicle body2. As aforementioned, the battery pack40is fixed to the rockers10via the EA members20(energy absorbing members20) at lower right and lower left parts of the vehicle body2. The left part of the lower structure3of the vehicle body2will be described hereinafter. The vehicle body2is symmetrical with respect to the left-right direction, thus the right part of the lower structure3of the vehicle body2has the same structure as that ofFIG. 2. That is, the vehicle body lower structure3of the embodiment comprises the pair of rockers10and the pair of EA members20, and each of the EA members20is arranged along corresponding one of the pair of rockers10. Hereinafter, one of the rockers10that is arranged at the left part of the vehicle body2(left rocker10) and one of the EA members20that is fixed to this rocker10will be described.

The battery pack40comprises a lower cover41, an upper cover42, and a plurality of battery cells43. A container is configured by the lower cover41and the upper cover42, and the plurality of battery cells43is housed within the container. Each of the lower cover41and the upper cover42is provided with a flange, and the container is configured by the flanges of the lower cover41and the upper cover42being joined.

The rocker10is configured of a rocker inner panel11and a rocker outer panel12. The rocker inner panel11has a square U shape (a channel shape) and is disposed with the U shape lying down on its side. The rocker inner panel11includes a lower flange11aand an upper flange11b. The lower flange11aextends downward from a lower edge of the lying U shape of the rocker inner panel11. The upper flange11bextends upward from an upper edge of the lying U shape of the rocker inner panel11. The rocker outer panel12has the same shape as the rocker inner panel11. The rocker outer panel12includes a lower flange12aand an upper flange12b, and the lower flange12aand the upper flange12bface the lower flange11aand the upper flange11bof the rocker inner panel11, respectively. The lower flanges11aand12aare welded to each other and the upper flanges11band12bare welded to each other, which results in the rocker10having a hollow rectangular tube shape. InFIG. 2, the rocker outer panel12is depicted apart from the rocker inner panel11to help understanding.

A bulkhead60is arranged in the rocker10. The bulkhead60is a reinforcement member for enhancing strength of the rocker10. The bulkhead60is attached to inside of the rocker inner panel11before the rocker inner panel11and rocker outer panel12are joined to each other. The bulkhead60is fixed to the rocker inner panel11by welding or with a bolt (not shown). A nut32is fixed to inside of the bulkhead60by welding. The bulkhead60will be described later.

The EA member20is configured of a first EA member21and a second EA member22. The first EA member21is arranged under the rocker10. The second EA member22is arranged between the first EA member21and the battery pack40. The first EA member21is fixed to the rocker10. The second EA member22is connected to the first EA member21and also connected to the battery pack40.

The EA member20(each of the first EA member21and the second EA member22) has a hollow rectangular tube shape. In other words, the EA member20(each of the first EA member21and the second EA member22) is a hollow beam. The EA member20is configured to absorb collision energy caused by a lateral collision to the vehicle to protect the battery pack40. The EA member20is configured to absorb the collision energy by being crushed in the vehicle-width direction by an impact of the collision. The rocker10also contributes to absorption of the collision energy, however, the rocker10alone may be insufficient to absorb all the collision energy on its own. To address this, the hollow EA member20is arranged along the rocker10.

Strength of the EA member20is determined in advance, for example, by simulation such that the EA member20can effectively absorb the collision energy. An inner space of the first EA member21is partitioned into several cell spaces CS by a plurality of partition plates25which connects an upper plate23and a lower plate24of the first EA member21to each other. The strength of the EA member20can be adjusted by appropriately selecting the number and/or thicknesses of the partition plates25. The strength of the FA member20is set lower than at least strength of the battery pack40.

As aforementioned, the first EA member21is arranged under the rocker10. Meanwhile, the rocker10is provided with the lower flange11a(12a) extending downward from a bottom plate13of the rocker10. The first EA member21needs to be arranged such that it can avoid interference with the lower flange11a(12a). If the first EA member21is divided into an inner portion and an outer portion relative to the lower flange11a(12a), the structure of the EA member thereby becomes complex. It should be noted that the “inner portion relative to the lower flange11a(12a)” means a portion of the first EA member21that is closer to a vehicle center than the lower flange11a(12a) in the vehicle-width direction. Similarly, the “outer portion relative to the lower flange11a(12a)” means a portion of the first EA member21that is farther from the vehicle center than the lower flange11a(12a) in the vehicle-width direction.

In the vehicle body lower structure3of the embodiment, the interference between the first EA member21and the lower flange11a(12a) can be avoided by a collar30being arranged between the first EA member21and the rocker10. Placing the first EA member21under the lower flange11a(12a) allows the first EA member21to have a simple shape and extend to a position that is on outer side relative to the lower flange11a(12a) in a vehicle-width direction.

The collar30is a metal cylinder. In other words, the collar30is a spacer configured to secure a clearance between the rocker10and the first EA member21. As shown inFIG. 2, a height h1of the collar30above the first EA member21is greater than a height h2of the lower flange11a(12a). The collar30secures a clearance of distance h1between the bottom plate13of the rocker10and the upper plate23of the first EA member21. Because the height of the lower flange11a(12a) is h2(<h1), the lower flange11a(12a) does not interfere with the first EA member21. Thus, a simple rectangular tube shape can be employed as the shape of the first EA member21, manufacturing costs for the EA member21can thereby be reduced.

A structure around the collar30will be described. The collar30passes through a hole23aprovided in the upper plate23of the first EA member21. An upper end of the collar30is in contact with a lower surface of the bottom plate13of the rocker10. A lower end of the collar30is in contact with an upper surface of the lower plate24of the first EA member21. The first EA member21, the rocker10, and the bulkhead60are joined together and fixed to each other with a bolt31passing through the collar30and the nut32.

When the battery pack40vibrates up and down while the vehicle is running, the collar30also vibrates up and down, and thus a vibration load is applied to the rocker10in an up-down direction. A deformation of the rocker10caused by the vibration load applied from the collar30is small because the bulkhead60and the bottom plate13are arranged between the collar30and the nut32.

A support plate44extends outward from a lower surface of the battery pack40in the vehicle-width direction. The support plate44and the first EA member21are also joined together and fixed to each other with the bolt31and the nut32. The battery pack40can be fixed to the EA member20firmly by fixing the support plate44extending from the battery pack40to the first EA member21.

A connecting structure of the first EA member21and the second EA member22will be described. A flange26extends from an end of the upper plate23of the first EA member21towards the vehicle center in the vehicle-width direction. The second EA member22is fixed to the flange26of die first EA member21with a bolt33and a nut34. The support plate44extending from the battery pack40is also fixed to the second EA member22with the bolt33. The second EA member22is held and fixed between the flange26of the first EA member21and the support plate44of the battery pack40. The second EA member22is bonded to a side surface of the lower cover41of the battery pack40. The battery pack40and the second EA member22are fixed firmly to each other with the bolt33and adhesive material.

The EA member20is divided into the first EA member21which is fixed to the rocker10and the second EA member22which is bonded to the battery pack40. The second EA member22is detachable from the first EA member21. The EA member20can be applied to a variety of vehicles having different body widths by selecting a second EA member having an appropriate width from among a variety of second EA members22having different widths and combining the selected second EA member22with the first EA member21.

The bottom view of the vehicle body2is shown inFIG. 3. The EA member20(the first EA member21) and the rocker10is joined together with the plurality of bolts31arranged in the front-rear direction of the vehicle. As shown inFIG. 2, each of the plurality of bolts31passes through a corresponding collar30and fixes the first EA member21to the rocker10. The EA members20(the first EA members21) and the rockers10are connected firmly to each other with a fewer bolts because they are joined together with the bolts. InFIG. 3, the collars30are omitted.

A plurality of bulkheads60is arranged in each of the rockers10along the front-rear direction of the vehicle. Each of the plurality of bulkheads60is also joined together with a corresponding EA member20(corresponding first EA member21) with the bolt31. Each single bolt31fixes the EA member20(the first EA member21) to the rocker10and also fixes one of the bulkheads60to the rocker10. The structure described above is simple and enable weight reduction as compared to a structure in which the EA member20and the bulkheads60are separately fixed to the rocker10.

A plurality of support plates44of the battery pack40is also arranged along the front-rear direction of the vehicle. Each of the plurality of support plates44extends outward from the battery pack40in the vehicle-width direction. Each of the support plates44is fixed to a corresponding EA member20(corresponding first EA member21and second EA member22) with the bolts31,33.

Crossmembers45extending in the vehicle-width direction are provided on the lower cover41of the battery pack40. The crossmembers45are elongated protrusions provided on the lower cover41. Each of the support plates44is connected to an end of a corresponding crossmember45. The strength of connection between the battery pack40and the EA members20is enhanced by attaching the support plates44to the ends of the crossmembers45and fixing the support plates44to the EA members20.

The bulkheads60will be described. Each bulkhead60is a reinforcement member formed by bending one metal plate. Each bulkhead60is also joined together with the corresponding EA member20(the corresponding first EA member21) with the bolt31. The bulkheads60are efficiently fixed by being joined together with the EA members20.

FIG. 4shows a perspective view of one bulkhead60. The bulkhead60is configured of a bottom plate61, atop plate62, a pair of side plates63, and aback plate64. A through hole65is provided in the bottom plate61. The bolt31passes through the through hole65. The nut32shown inFIG. 2is welded to the bottom plate61such that a center line of the nut32coincides with a center line of the through hole65. The nut32is omitted inFIG. 4.

The bulkhead60is attached to the inside of the rocker inner panel11before the rocker inner panel11and the rocker outer panel12are joined to each other to form the rocker10.

As aforementioned, the plurality of bulkheads60is arranged in each of the rockers10.FIG. 5shows aside view of the lower part of one center pillar51(refer toFIG. 1).FIG. 5shows cross sections of the rocker10, the first EA member21, the collars30, the support plates44, and bolts31. As shown inFIG. 5, the bulkheads60are arranged also under the center pillar51. In other words, at least one of the plurality of bulkheads60is arranged to overlap with the center pillar51when viewed in the up-down direction. The center pillar51is a kind of frame that secures the strength of the vehicle body2. Especially, the center pillar51secures the strength against rollover of the vehicle. The strength against rollover of the vehicle can be improved by arranging at least one bulkhead60under the center pillar51.

As aforementioned, each bulkhead60is formed by bending a metal plate.FIG. 4is a schematic diagram of one bulkhead60and omits details of the shape of the bulkhead60. The shape shown inFIG. 4is an example of the shape of the bulkhead60. The bulkhead60may have various shapes such as bulkheads60ato60cshown inFIGS. 6A to 6C, for example.

Points to be noted with regard to the art described in the embodiment will be described. Cross sectional shapes of the EA member20(the first EA member21, the second EA member22) cut along planes perpendicular to the front-rear direction of the vehicle are identical regardless of the cutting positions along the front-rear direction. The EA member20(the first EA member21, the second EA member22) may be formed by extrusion molding of metal (typically, aluminum).

One bulkhead60may be fixed to the rocker10with single bolt31. Or, one bulkhead60may be fixed to the rocker10with a plurality of bolts. Each of the bolts fixing one bulkhead60may pass through corresponding one of the collars30, and the bolts may fix the EA member20to the rocker10via the collars30.

The battery pack40is an example of “power source”. The battery pack40houses the plurality of battery cells. The power source arranged adjacent to the rocker10is not limited to the battery pack40. The power source may be a device housing capacitors or a device housing fuel cells.

Each EA member20(each of the first EA members21and the second EA members22) is a hollow beam having a rectangular tube shape. Therefore, “the first EA member” may be called as “the first hollow beam” and “the second EA member” may be called as “the second hollow beam”.

While specific examples of the present disclosure have been described above in detail, these examples are merely illustrative and place no limitation on the scope of the patent claims. The technology described in the patent claims also encompasses various changes and modifications to the specific examples described above. The technical elements explained in the present description or drawings provide technical utility either independently or through various combinations. The present disclosure is not limited to the combinations described at the time the claims are filed. Further, the purpose of the examples illustrated by the present description or drawings is to satisfy multiple objectives simultaneously, and satisfying any one of those objectives gives technical utility to the present disclosure.