VEHICLE UNDERFLOOR STRUCTURE

Technical Field

[0001] The present invention relates to a vehicle underfloor structure.

Background Art

[0002] There are conventionally known underfloor flow adjusting structures of automobiles that, by providing a flow adjusting member at the vehicle lower side of a vehicle body floor, can adjust the airflow that flows at the vehicle lower side of the vehicle body floor (see, for example, Japanese Patent No. 4227003).

SUMMARY OF INVENTION

Technical Problem

[0003] However, in the underfloor flow adjusting structure of an automobile that is disclosed in aforementioned Japanese Patent No. 4227003, the vehicle body floor and the vehicle rear side end portion of the surface at the vehicle front side of the flow adjusting member are separated in the vehicle vertical direction. Therefore, it can be thought that it is difficult to sufficiently adjust the airflow that flows toward the vehicle rear side of the flow adjusting member. Further, if the inclination angle of the surface at the vehicle front side of the flow adjusting member is set to a small angle, it is advantageous in adjusting the airflow that flows toward the vehicle rear side of the flow adjusting member. However, if the inclination angle of this surface is set to a small angle, a larger space is needed for placement of the flow adjusting member.

[0004] Accordingly, there are cases in which it is difficult to realize both ensuring of the flow adjusting effect on the airflow that flows at the vehicle lower side of a vehicle body floor and ensuring of space at the vehicle lower side of the vehicle body floor.

[0005] In view of the above-described circumstances, an object of the present invention is to obtain a vehicle underfloor structure that can realize both ensuring of the flow adjusting effect on the airflow that flows at the vehicle lower side of a vehicle body floor and ensuring of space at the vehicle lower side of the vehicle body floor.

Solution to Problem

[0006] A vehicle underfloor structure relating to a first aspect of the present invention comprises: a vehicle body floor; an undercover having, at a vehicle vertical direction lower side of the vehicle body floor and at a predetermined interval from the vehicle body floor, a cover main body portion that extends in a vehicle transverse direction and a vehicle longitudinal direction; and an inclined portion that is provided integrally from a vehicle longitudinal direction front side end portion of the cover main body portion, and that is formed in a shape that is convex toward a vehicle lower front side, and that is structured to include a plurality of inclined surface portions that are inclined from a vehicle upper front side toward a vehicle lower rear side.

[0007] In a vehicle underfloor structure relating to a second aspect of the present invention, in the invention relating to the first aspect, a supplementary angle of an angle formed by the cover main body portion and one inclined surface portion that is adjacent to the cover main body portion, and a supplementary angle of an angle formed by the one inclined surface portion and an inclined surface portion that is adjacent at a vehicle front side of the one inclined surface portion, are each smaller than 45°.

[0008] In a vehicle underfloor structure relating to a third aspect of the present invention, in the invention relating to the first or second aspect, the inclined portion is structured by three of the inclined surface portions.

[0009] In a vehicle underfloor structure relating to a fourth aspect of the present invention, in the invention relating to any one of the first through third aspects, the undercover can be disposed at a predetermined interval from a tire, that is disposed at a vehicle longitudinal direction front side of the inclined portion, such that a vehicle part can be disposed between the inclined portion and the tire.

[0010] In accordance with the invention relating to the first aspect of the present invention, the cover main body portion extends in the vehicle transverse direction and the vehicle longitudinal direction, at the vehicle vertical direction lower side of the vehicle body floor at a predetermined interval from the vehicle body floor. Therefore, a space is formed between the undercover and the vehicle body floor, and various members can be placed in this space.

[0011] Here, in the present invention, the inclined portion, that is formed in a shape that is convex toward the vehicle lower front side, is provided integrally with the cover main body portion from the vehicle longitudinal direction front side end portion of the cover main body portion. This inclined portion is structured to include plural inclined surface portions that are inclined from the vehicle upper front side toward the vehicle lower rear side. Therefore, a space can be sufficiently ensured between the undercover and the vehicle body floor, and airflow, that flows from the vehicle front side, can be adjusted in a direction along the inclined portion, and this airflow can be made to flow along the cover main body portion.

[0012] In accordance with the invention relating to the second aspect of the present invention, the supplementary angle of the angle formed by the cover main body portion and the inclined surface portion that is adjacent to the cover main body portion, and the supplementary angle of the angle formed by an inclined surface portion and the inclined surface portion that is adjacent at the vehicle front side of the aforementioned inclined surface portion, are set to angles that are smaller than 45°. Due thereto, of the velocity components of the airflow that flows along an inclined surface portion, the proportion of the velocity component, in the direction along the cover main body portion or the inclined surface portion that is adjacent at the vehicle rear side of that inclined surface portion, can be made to be large.

[0013] In accordance with the invention relating to the third aspect of the present invention, the inclined portion is structured by three inclined surface portions. Due thereto, the direction of the flow of the airflow, that flows along the inclined portion, can be changed gradually.

[0014] In accordance with the invention relating to the fourth aspect of the present invention, the undercover can be disposed at a predetermined interval such that a vehicle part can be disposed between the inclined portion and a tire that is disposed at the vehicle longitudinal direction front side of the inclined portion. Due thereto, a vehicle part can be disposed between the inclined portion and the tire that is disposed at the vehicle longitudinal direction front side of the inclined portion.

Advantageous Effects of Invention

[0015] As described above, the vehicle underfloor structure relating to the first aspect of the present invention has the excellent effect that ensuring of the flow adjusting effect on the airflow that flows at the vehicle lower side of the vehicle body floor, and ensuring of a space at the vehicle lower side of the vehicle body floor, can both be realized.

[0016] The vehicle underfloor structure relating to the second aspect of the present invention has the excellent effect that separation of the airflows that flow along the inclined surface portions and the cover main body portion can be suppressed or prevented.

[0017] The vehicle underfloor structure relating to the third aspect of the present invention has the excellent effect that the airflow that flows along the inclined portion can be merged gently with the airflow that flows at the vehicle lower side of the undercover, and an increase in traveling resistance (air resistance) due to disturbance of this airflow can be suppressed or prevented.

[0018] The vehicle underfloor structure relating to the fourth aspect of the present invention has the excellent effect that the space formed between the inclined portion and a tire, that is disposed at the vehicle longitudinal direction front side of the inclined portion, can be utilized effectively.

BRIEF DESCRIPTION OF DRAWINGS

[0019] Fig. 1 is an enlarged sectional view showing main portions of a vehicle underfloor structure relating to a first embodiment (an enlarged sectional view showing main portions of Fig. 2).

Fig. 2 is an enlarged sectional view showing the vehicle underfloor structure relating to the first embodiment (an enlarged sectional view showing a state cut along line 2-2 of Fig. 4). Fig. 3 is a perspective view showing the vehicle underfloor structure relating to the first embodiment.

Fig. 4 is a bottom view that is seen from a vehicle lower side and shows the vehicle

underfloor structure relating to the first embodiment.

Fig. 5 is an enlarged sectional view showing main portions of a vehicle underfloor structure relating to a second embodiment.

Fig. 6 is a cross-sectional view showing a modified example of the vehicle underfloor structure relating to the second embodiment.

DESCRIPTION OF EMBODIMENTS

[0020] A first embodiment of a vehicle underfloor structure relating to the present invention is described hereinafter by using Fig. 1 through Fig. 4. Note that arrow FR that is shown appropriately in these drawings indicates the vehicle front side, arrow UP indicates the vehicle upper side, and arrow OUT indicates the vehicle transverse direction outer side.

[0021] First, an example of the lower portion structure of a vehicle 10 relating to the present embodiment is described by using Fig. 3 and Fig. 4. As shown in these drawings, rockers 14, that structure portions of a vehicle body skeleton, extend along the vehicle longitudinal direction at the vehicle transverse direction both end portions of a vehicle body 12. The rocker 14 is made into a closed cross-sectional structure that has a rectangular cross-section, by an outer panel 16 that structures the vehicle transverse direction outer side of the rocker 14, and an inner panel 18 that structures the vehicle transverse direction inner side of the rocker 14. Note that, in Fig. 3, that rockers 14 are illustrated in a simplified manner. Further, a floor panel 22 extends in the vehicle longitudinal direction between the left and right rockers 14, and a vehicle body floor 20 of the vehicle body 12 is structured by this floor panel 22. The floor panel 22 is structured by a plate material that is rectangular in plan view, and the vehicle transverse direction both end portions of this floor panel 22 are bent and made into flange portions 22A. Further, the floor panel 22 is fixed to the rockers 14 due to the flange portions 22 A being joined by spot welding or the like to the vehicle lower sides of the inner panels 18. Note that front tires 24 are disposed at the vehicle front sides of the rockers 14, and rear tires 26 are disposed at the vehicle rear sides of the rockers 14.

[0022] An energy absorbing member 28 is provided at the vehicle lower side of the rocker 14. This energy absorbing member 28 is formed in a rectangular parallelepiped shape that extends in the vehicle longitudinal direction by extrusion molding an aluminum material, and can absorb collision energy at the time of a side collision. Note that the energy absorbing member 28 is mounted by unillustrated bolts or the like to the surface at the vehicle lower side of the rocker 14.

[0023] Here, in the present embodiment, the vehicle underfloor structure is structured to include an undercover 30. The vehicle lower sides of the floor panel 22 and the energy absorbing members 28 are covered by the undercover 30. Hereinafter, the structure of the vehicle undercover structure, that centers on the undercover 30 that is a main portion of the present invention, is described in detail.

[0024] As shown in Fig. 2 through Fig. 4, the undercover 30 is formed to integrally include a cover main body portion 32, a front cover portion 36, and inclined portions 38. The cover main body portion 32 is formed in the shape of a rectangular plate that extends in the vehicle transverse direction and the vehicle longitudinal direction as seen in plan view, and is disposed at the vehicle lower sides of the energy absorbing members 28 in a horizontal state with respect to the vehicle body floor 20. Namely, the cover main body portion 32 is disposed at the vehicle lower side of the vehicle body floor 20 with a predetermined interval between the cover main body portion 32 and the vehicle body floor 20, and a space 62 is formed by this cover main body portion 32 and the vehicle body floor 20. Further, the vehicle rear side end portion of the cover main body portion 32 is disposed so as to be offset, by a predetermined distance toward the vehicle rear side, from the vehicle rear side end portions of the energy absorbing members 28. Moreover, the vehicle transverse direction both end portions of the cover main body portion 32 are disposed so as to be offset, by a predetermined distance toward the vehicle transverse direction inner side, from the vehicle transverse direction outer side end portions of the energy absorbing members 28. The vehicle transverse direction outer sides of the energy absorbing members 28 are in a state of being exposed as seen from the vehicle lower side. Note that the cover main body portion 32 is set so as to be in a state of being close to a road surface 54 at the time when the vehicle travels.

[0025] The front cover portion 36 is provided integrally with the cover main body portion 32 from the vehicle transverse direction central portion of an end portion 32A at the vehicle longitudinal direction front side of the cover main body portion 32. This front cover portion 36 is structured in a U-shape whose vehicle upper side is open as seen in a longitudinal sectional view, by a lower wall portion 36A that faces the vehicle lower side and a pair of side wall portions 36B that face the vehicle transverse direction outer sides. The lower wall portion 36A is formed in the shape of a trapezoidal plate as seen in plan view, and more concretely, is formed in the shape of a trapezoidal plate whose side at the upper side is made to be the vehicle front side and that is set so as to be symmetrical with respect to the vehicle transverse direction center of the cover main body portion 32. This lower wall portion 36A is provided at the end portion 32 A at the vehicle longitudinal direction front side of the cover main body portion 32, in a state of being inclined from the vehicle upper front side toward the vehicle lower rear side. The side wall portions 36B are provided at the vehicle transverse direction outer side both end portions of the lower wall portion 36A along these end portions so as to be substantially V-shaped as seen in plan view. At these side wall portions 36B, the vehicle front side end portions are set so as to run along the vehicle vertical direction, and the vehicle upper side end portions are set so as to run along the vehicle body floor 20, and the side wall portions 36B are formed in quadrangular plate shapes that extend toward the vehicle lower rear side as seen in side view. Further, the inclined portions 38 are provided at the vehicle transverse direction outer sides of the side wall portions 36B. Note that, as shown in Fig. 2, mounting holes 34, that are shaped as cylindrical tubes having covers and whose vehicle lower sides are open, are provided at plural places of the front cover portion 36 and the cover main body portion 32, and unillustrated insert-through holes are provided in the centers of cover portions 34A of these mounting portions 34. On the other hand, an unillustrated reinforcing member is provided at the vehicle lower side of the vehicle body floor 20, and unillustrated screw holes, that correspond to the insert-through holes of the cover portions 34A, are provided in this reinforcing member and the energy absorbing members 28. Further, fastening members, such as unillustrated screws or the like, are inserted-through these insert-through holes from the vehicle lower side, and, due to the fastening members being screwed-together with these screw holes, the undercover 30 is fixed to the vehicle lower side of the vehicle body floor 20.

[0026] As shown in Fig. 1 , the inclined portions 38 are provided integrally with the cover main body portion 32 from the vehicle transverse direction outer side portions of the end portion 32A at the vehicle longitudinal direction front side of the cover main body portion 32. The inclined portion 38 is formed in a shape that is convex toward the vehicle lower front side by an inclined surface portion 40, an inclined surface portion 42, and an inclined surface portion 44 that are inclined from the vehicle upper front side toward the vehicle lower front side and are formed in rectangular plate shapes, respectively. The inclined surface portion 40 is disposed adjacent to the cover main body portion 32 at the end portion 32 A of the cover main body portion 32, and the supplementary angle of the angle formed by the inclined surface portion 40 and the cover main body portion 32 is set to θ _1; and the width of the inclined surface portion 40 as seen in side view is set to Li. The inflection portion (the end portion 32A) of this inclined surface portion 40 and the cover main body portion 32 is set so as to be further toward the vehicle rear side than the vehicle front side end portion of the energy absorbing member 28. In other words, the inclined surface portion 40 is disposed such that this inclined surface portion 40 and the front side of the energy absorbing member 28 overlap as seen from the vehicle lower side. The inclined surface portion 42 is disposed adjacent to the inclined surface portion 40 at the vehicle front side end portion of the inclined surface portion 40, and the supplementary angle of the angle formed by the inclined surface portion 42 and the inclined surface portion 40 is set to θ ₂ , and the width of the inclined surface portion 42 as seen in side view is set to L ₂ . The inclined surface portion 44 is disposed adjacent to the inclined surface portion 42 at the vehicle front side end portion of the inclined surface portion 42, and the supplementary angle of the angle formed by the inclined surface portion 44 and the inclined surface portion 42 is set to θ ₃ , and the width of the inclined surface portion 44 as seen in side view is set to L ₃ . Further, the angle of inclination of the inclined surface portion 44 with respect to the vehicle vertical direction is set to θ ₄ . In the present embodiment, as an example, these angles are set to θι = θ ₂ = θ ₃ = θ = 22.5°, and, in other words, the relationship θι = . . . = ΘΝ = 90°/(N+l) (where N is the number of inclined surface portions) is established. Further, the ratio of Ly, L ₂ and L ₃ is set to Lf.L ₂ :L ₃ - 1 :2:2, or in other words, Li is set to a short length as compared with L ₂ and L ₃ . Note that, as shown in Fig. 4, a predetermined interval D is ensured between the inclined surface portion 38 and the front tire 24, and a predetermined length of the rocker 14 is exposed as seen from the vehicle lower side (hereinafter, this portion is called the "exposed portion 14A").

Therefore, various members can be placed at the exposed portion 14A. Note that, in the present embodiment, a jack-up point 46 is set at the exposed portion 14 A, and this jack-up point 46 is exposed from the vehicle lower side.

[0027] Operation/effects of the present embodiment are described next.

[0028] In the present embodiment, as shown in Fig. 1 and Fig. 2, the cover main body portion 32 extends in the vehicle transverse direction and the vehicle longitudinal direction, at the vehicle lower side of the vehicle body floor 20 and with a predetermined interval between the cover main body portion 32 and the vehicle body floor 20. Therefore, the space 62 is formed between the under cover 30 and the vehicle body floor 20, and the energy absorbing members 28 can be disposed in this space 62.

[0029] By the way, in the present embodiment, the inclined portion 38 is formed, by the plural inclined surface portions, in a shape that is convex toward the vehicle lower front side. If the inclined portion 38 were to be structured by a single inclined surface portion, there would be cases in which the space at the vehicle lower side of the vehicle body floor 20 would not be able to be utilized effectively. To describe this more concretely, in a case in which the inclined portion 38 were to be structured by a single inclined surface portion such as imaginary line K shown in Fig. 1, the length in the vehicle longitudinal direction of the energy absorbing member 28 would have to be made to be shorter in order to prevent interference of the vehicle front side end portion of the energy absorbing member 28 with the inclined portion 38. As a result, of the space 62 between the cover main body portion 32 and the vehicle body floor 20, there would be cases in which a space 62A, that is partitioned by the inclined portion 38 and the imaginary line K as seen in side view, would be dead space. Further, if the inclined portion 38 was made to be long in the vehicle longitudinal direction in order to maintain the outer dimensions of the energy absorbing member 28, the exposed portion 14A of the rocker 14 at the vehicle front side of the inclined portion 38 would shrink, and there would be cases in which it would be difficult to set the jack-up point 46 at this exposed portion 14 A.

[0030] However, in the present embodiment, the inclined portions 38 are formed in a shape that is convex toward the vehicle lower front side, by the inclined surface portion 40, the inclined surface portion 42, and the inclined surface portion 44. Due thereto, the space 62 between the undercover 30 and the vehicle body floor 20 can be ensured sufficiently, and accordingly, the space at the vehicle lower side of the vehicle body floor 20 can be utilized effectively.

[0031] Further, in the present embodiment, airflow W _l5 that flows from the vehicle front side at the vehicle lower side of the vehicle body floor 20, can be adjusted by the undercover 30.

[0032] To describe this concretely by using Fig. 1 through Fig. 4, at the time when the vehicle 10 is traveling, the airflow W _\ that flows from the vehicle front side is, as shown in Fig. 4, made to flow along the side wall portions 36B of the front cover portion 36, and is adjusted so as to flow toward the inclined portions 38.

[0033] As shown in Fig. 1 and Fig. 2, the airflow Wj that is adjusted toward the inclined portion 38 flows along the inclined surface portion 40, the inclined surface portion 42 and the inclined surface portion 44 of the inclined portion 38, and is adjusted so as to run along the cover main body portion 32. Further, the airflow is merged with airflow W ₂ , that flows in a vicinity of the road surface 54, so as to become a single airflow W ₃ , and this airflow W ₃ flows along the cover main body portion 32.

[0034] Further, in the present embodiment, a flow path 56 is formed by the inclined portion 38, the cover main body portion 32 and the road surface 54. A flow entrance 58 of this flow path 56 is structured to include the vehicle upper side end portion of the inclined surface portion 44 and the road surface 54, and the cross-sectional area of this flow entrance 58 is set to be Ai . On the other hand, a flow exit 60 of the flow path 56 is structured to include the vehicle rear side end portion of the cover main body portion 32 and the road surface 54, and the cross-sectional area of this flow exit 60 is set to be A ₂ . The relationship between the cross-sectional area Ai and the cross-sectional area A ₂ is set to be Ai > A ₂ . Therefore, the airflow Wi and the airflow W ₂ flow-in from the flow entrance 58 of the flow path 56 and become the airflow W ₃ , and when passing along the vehicle lower side of the cover main body portion 32 at this flow path 56, the flow velocity of the airflow W ₃ becomes faster due to the continuity equation of incompressible fluid. Namely, flow velocity V ₂ , at the time when the airflow W ₃ passes along the vehicle lower side of the cover main body portion 32 at the flow path 56, is faster than flow velocity Vy of the airflow Wi and the airflow W ₂ before flowing into the flow entrance 58. Moreover, the cover main body portion 32 is set in a state of being near the road surface 54 at the time when the vehicle travels, and therefore, the flow velocity V ₂ of the airflow W ₃ that flows at the vehicle lower side of the cover main body portion 32 can be increased sufficiently. Accordingly, a low pressure (negative pressure) region is formed at the vehicle lower side of the cover main body portion 32 due to

Bernoulli's theorem, and as a result, downforce is generated at the vehicle 10.

[0035] In this way, in the present embodiment, the inclined portions 38, that are formed in shapes that are convex toward the vehicle front lower side, are provided integrally with the cover main body portion 32 from the end portion 32A at the vehicle longitudinal direction front side of the cover main body portion 32 of the undercover 30. Further, the inclined portions 38 are structured by the plural inclined surface portions (the inclined surface portions 40, the inclined surface portions 42, and the inclined surface portions 44) that are inclined from the vehicle upper front sides toward the vehicle lower rear sides. Thus, the space 62 can be sufficiently ensured between the undercover 30 and the vehicle body floor 20, and the airflow Ψγ that flows from the vehicle front side can be adjusted in directions along the inclined portions 38, and this airflow Wi can be made to flow along the cover main body portion 32. As a result, ensuring of the flow adjusting effect on the airflow that flows at the vehicle lower side of the vehicle body floor 20, and ensuring of the space 62 at the vehicle lower side of the vehicle body floor 20, can both be realized.

[0036] Further, in the present embodiment, the supplementary angle Q\ of the angle, that is formed by the cover main body portion 32 and the inclined surface portion 40 that is adjacent to the cover main body portion 32, is set to an angle that is less than 45°. Further, the supplementary angle θ ₂ of the angle, that is formed by the inclined surface portion 40 and the inclined surface portion 42 that is adjacent at the vehicle front side of this inclined surface portion 40, and the supplementary angle θ ₃ of the angle, that is formed by the inclined surface portion 42 and the inclined surface portion 44 that is adjacent at the vehicle front side of this inclined surface portion 42, are set to angles that are smaller than 45°. Thus, of the velocity components of the airflow that flows along the inclined surface portion 40, the proportion of the velocity component in the direction along the cover main body portion 32 can be made to be large. Further, among the velocity components of the airflow that flows along an inclined surface portion, the proportion of the velocity component in the direction along the inclined surface portion, that is adjacent at the vehicle rear side of the aforementioned inclined surface portion, can be made to be large. As a result, separation of the airflows, that flow along the inclined surface portion 40, the inclined surface portion 42, the inclined surface portion 44 and the cover main body portion 32, can be suppressed or prevented.

[0037] Moreover, in the present embodiment, the inclined portion 38 is structured by the three inclined surface portions (the inclined surface portion 40, the inclined surface portion 42 and the inclined surface portion 44). Due thereto, the direction of the flow of the airflow Wi, that flows along the inclined portion 38, can be changed gradually, and as a result, the airflow Wi that flows along the inclined portion 38 can be merged gently with the airflow W ₂ that flows at the vehicle lower side of the undercover 30, and an increase in traveling resistance (air resistance) caused by disturbance of this airflow W ₂ can be suppressed or prevented.

[0038] In addition, in the present embodiment, the undercover 30 can be placed so as to be apart by the predetermined interval D such that vehicle parts can be placed between the inclined portions 38 and the front tires 24 that are disposed at the vehicle longitudinal direction front sides of these inclined portions 38. Due thereto, the jack-up points 46 can be disposed between the inclined portions 38 and the front tires 24 that are disposed at the vehicle longitudinal direction front sides of these inclined portions 38. As a result, the spaces, that are formed between the inclined portions 38 and the front tires 24 that are disposed at the vehicle longitudinal direction front sides of these inclined portions 38, can be utilized effectively.

[0039] Still further, in the present embodiment, the flow path 56 is formed by the inclined portions 38, the cover main body portion 32 and the road surface 54, and the cover main body portion 32 is set so as to be in a state of being near the road surface 54 at the time when the vehicle travels. Therefore, downforce can be generated at the vehicle 10, and as a result, the ground contacting ability at the time when the vehicle travels, of the front tires 24 and the rear tires 26, can be improved.

[0040] <Second Embodiment

A second embodiment of the vehicle underfloor structure relating to the present invention is described next. Note that structural portions that are the same as those of the

above-described first embodiment are denoted by the same numbers, and description thereof is omitted.

[0041] As shown in Fig. 5, this second embodiment has features in the point that an inclined portion 80 is structured by two inclined surface portions, and the point that a curved surface portion 86 is provided at the vehicle rear side of the inclined portion 80.

[0042] To describe this concretely, the inclined portion 80 in the present embodiment is structured by an inclined surface portion 82 and an inclined surface portion 84 that are basically structured similarly to the inclined surface portions of the first embodiment. The inclined surface portion 82 is disposed adjacent to the cover main body portion 32 at the front end 32A at the vehicle longitudinal direction front side of the cover main body portion 32, and the supplementary angle of the angle formed by this inclined surface portion 82 and the cover main body portion 32 is set to φ _1; and the width of the inclined surface portion 82 as seen in side view is set to St. The inclined surface portion 84 is disposed adjacent to the inclined surface portion 82 at the vehicle front side end portion of the inclined surface portion 82, and the supplementary angle of the angle formed by the inclined surface portion 84 and the inclined surface portion 82 is set to φ ₂ , and the width of the inclined surface portion 84 as seen in side view is set to S ₂ . Further, the angle of inclination of the inclined surface portion 84 with respect to the vehicle vertical direction is set to φ ₃ . In the present embodiment, as an example, these angles are set to φι = φ ₂ = φ ₃ = 30°, and in the present embodiment as well, the relationship φι = ... = φκ = 90°/(N+l) (where N is the number of inclined surface portions) is established. Further, the ratio of Si and S ₂ is set to Sj :S ₂ = 1 : 1. Further, the curved surface portion 86, that is formed in a circumferential shape that is convex toward the vehicle upper front side, is provided at the vehicle rear side end portion of the inclined surface portion 82, and the cover main body portion 32 is disposed at a position that is a predetermined height higher than the vehicle rear side end portion of the inclined surface portion 82, by an amount corresponding to the amount by which this curved surface portion 86 is provided.

[0043] Operation/effects of the present embodiment are described next.

[0044] In the present embodiment, the supplementary angle φ _! of the angle formed by the inclined surface portion 82 and the cover main body portion 32, and the supplementary angle φ ₂ of the angle formed by the inclined surface portion 84 and the inclined surface portion 82, are 30°, and are set to be large angles as compared with θϊ through θ ₃ in the first embodiment. However, the inclination angle φ ₃ , with respect to the vehicle vertical direction, of the inclined surface portion 84 is set to an angle that is larger than the inclination angle θ ₄ , with respect to the vehicle vertical direction, of the inclined surface portion 44 in the first embodiment.

Therefore, the inclined portion 80 can, overall, exhibit a flow adjusting effect that is similar to that of the inclined portion 38 of the first embodiment, and as a result, operation/effects that are similar to those of the above-described first embodiment are obtained in the present embodiment as well.

[0045] Further, in the present embodiment, the curved surface portion 86 is provided at the vehicle rear side end portion of the inclined surface portion 82, and this curved surface portion 86 is formed in a circumferential shape that is convex toward the vehicle upper front side. Therefore, the flow path of the airflow Wi, that flows at the vehicle lower side of the undercover 30, is extended by an amount corresponding to the amount over which the airflow flows along the curved surface portion 86, and the flow velocity of this airflow Wi becomes faster. As a result, a low pressure (negative pressure) region is formed at the vehicle lower side of the curved surface portion 86, and downforce can be generated at the vehicle 10.

[0046] A modified example of the second embodiment of the present invention is described next.

[0047] In the present embodiment, the cover main body portion 32 is disposed so as to be horizontal with respect to the vehicle body floor 20. However, as shown in Fig. 6, the cover main body portion 32 may be disposed in a state in which the inclination angle thereof with respect to the vehicle body floor 20 is set to a.

[0048] At the cover main body portion 32 that is structured in this way, the portion, at the vehicle lower side of the cover main body portion 32, of the flow path 56 enlarges gradually. Therefore, the pressure of the airflow W ₃ , that flows at the vehicle lower side of the cover main body portion 32, increases due to Bernoulli's theorem, and the air at the vehicle lower side of the cover main body portion 32 can be pushed-out to the vehicle rear side. As a result, a low pressure (negative pressure) region is formed at the vehicle front side of the cover main body portion, and downforce can be generated at the vehicle 10.

[0049] Further, the inclination angle φ ₃ , with respect to the vehicle vertical direction, of the inclined surface portion 84 becomes larger by an amount corresponding to the amount by which the cover main body portion 32 is inclined with respect to the vehicle body floor 20 (changes from 30° to 30°+a). Due thereto, traveling resistance (air resistance) due to the inclined surface portion 84 can be reduced. [0050] Supplementary Description of Above-Described Embodiments>

(1) In the above-described first embodiment, the angles are set to θι = θ ₂ = θ ₃ = θ ₄ = 22.5°, and the ratio of Li, L ₂ and L ₃ is set to i :L ₂ :L ₃ = 1 :2:2. However, the values of θι through θ ₄ and Li through L ₃ may be changed appropriately within ranges in which the above-described operation/effects are obtained.

[0051] (2) Further, in the above-described first embodiment, the cover main body portion 32 is formed in a rectangular plate shape, and is disposed so as to be horizontal with respect to the vehicle body floor 20. However, a structure that is similar to that of the second embodiment may be applied.

[0052] (3) In the above-described second embodiment, the angles are set to φι = φ ₂ = φ ₃ = 30°, and the ratio of Si and S ₂ is set to Sj :S ₂ = 1 : 1. However, the values of φι through φ ₃ and Si and S ₂ may be changed appropriately within ranges in which the above-described operation/effects are obtained.

[0053] (4) In the above-described embodiments, the jack-up points 46 are in states of being exposed as seen from the vehicle lower side. However, the jack-up points 46 may be made to be exposed only at times when the jack-up points 46 are used. As an example, the jack-up points 46 may be made to be able to be exposed by making the undercover 30 be a moveable structure.

[0054] (5) Further, in the above-described embodiments, the undercover 30 is structured so as to be fixed to the vehicle lower side of the vehicle body floor 20, but there may be a structure in which the position and the angle of this undercover 30 can be changed by an actuator or the like. As an example, there may be a structure in which the velocity, acceleration, steering angle, and the like are sensed by sensing means or the like, and the position and the angle of the undercover 30 are changed by an actuator or the like on the basis of the results of sensing by the sensing means.

[0055] (6) Moreover, in the above-described embodiments, there is a structure in which the energy absorbing members 28 are provided within the space 62, but there may be a structure in which other members are provided as appropriate. [0056] (7) In addition, although the jack-up points 46 are set at the exposed portions 14A of the rockers 14 in the above-described embodiments, there may be a structure in which other members are provided at the exposed portions 14A as appropriate.

[0057] (8) Still further, the shapes of the inclined portion 38 and the inclined portion 80 are not limited to those of the above-described embodiments, and the inclined portion 38 or the inclined portion 80 may be provided over the entire end portion 32A at the vehicle longitudinal direction front side of the cover main body portion 32. Further, the number of inclined surface portions also may be changed appropriately provided that it is within a range in which the above-described operation/effects are obtained. Note that the inclined portion

38 and the inclined portion 80 have a flow adjusting effect even if the length, in the vehicle transverse direction, of the inclined portion 38 or the inclined portion 80 is a short length.

[0058] The disclosure of Japanese Patent Application No. 2013-209544 is, in its entirety, incorporated by reference into the present Description. All publications, patent applications, and technical standards mentioned in the present Description are incorporated by reference into the present Description to the same extent as if such individual publication, patent application, or technical standard was specifically and individually indicated to be

incorporated by reference.