Lower vehicle body structure of vehicle

Abstract

The purpose of the present invention is to provide a lower vehicle body structure for a vehicle capable of ensuring desired lateral collision performance even if a floor panel is joined to the upper side of a side member at the center position in the vertical direction of the vehicle. The invention provides a lower vehicle body structure of a vehicle (1). A floor cross beam (6) connecting a pair of left and right side beams (3) is provided with: an upper beam (70) which is fixed to a floor panel upper surface (4a), which is the upper surface of a front floor panel (4), protrudes toward the upper part of the vehicle, and has a cross beam upper surface (711) facing the upper part of the vehicle; and a lower beam (80) which is fixed to a floor panel lower surface (4b), which is the lower surface of the front floor panel (4), and protrudes toward the lower part of the vehicle. The side member (3) and the floor cross member (6) are joined such that the positions of the side member upper surface (3c) and the cross member upper surface (711) are aligned in the vertical direction of the vehicle. The upper beam (70) and the lower beam (80) form a closed cross-section in a longitudinal cross-section in the front-rear direction by means of a front floor panel (4) disposed between the upper beam (70) and the lower beam (80).

Description

Technical Field

[0001] The present invention relates to a lower body structure of a vehicle, for example, to a structure in which a floor panel is joined to the upper side of the left and right side sills at the central position in the vertical direction of the vehicle. Background Technology

[0002] Generally speaking, the lower body structure of vehicles in recent years includes: side beams extending in the longitudinal direction of the vehicle and arranged in pairs, a floor panel disposed between the pairs of side beams, and a floor crossbeam fixed to the upper surface of the floor panel and connecting the pairs of side beams in the vehicle width direction.

[0003] In the lower body structure of the aforementioned vehicle, as shown in Patent Document 1, the collision load from the side of the vehicle during a side collision (hereinafter referred to as the side collision load) is transmitted to the opposite side in the vehicle width direction by a floor crossbeam that connects the left and right pairs of side beams in the vehicle width direction.

[0004] Specifically, the vehicle's lower body structure transfers the lateral impact load acting on one side of one of the paired side beams to the other side of the side beam via a floor crossbeam extending in the vehicle width direction.

[0005] Thus, in order to efficiently transfer lateral collision loads from one side beam to the other, the lower body structure of the vehicle needs to align the upper surfaces of the edges forming the side beams and the floor crossbeams in the vertical direction of the vehicle, and improve the cross-sectional strength of the floor crossbeams in the longitudinal section along the longitudinal direction of the vehicle (hereinafter referred to as the longitudinal section in the longitudinal direction).

[0006] However, as shown in Patent Document 1, for example, an electric vehicle has its battery located under the floor, so the floor panel may be positioned higher on the vehicle side than in a vehicle without the battery. In this case, the floor panel would engage with the side beam above the center of the vehicle in the vertical direction.

[0007] Thus, if the floor panel is joined to the upper side of the side beam at its central position in the vertical direction of the vehicle, although the upper surfaces of the relatively strong ridge portions forming in the side beam and the floor crossbeam can be aligned in the vertical direction of the vehicle, making the ridge portions continuous, the cross-sectional area in the longitudinal section of the floor crossbeam in the longitudinal direction will be smaller, which may not ensure sufficient cross-sectional strength. Therefore, it cannot be said that lateral collision loads can be efficiently transferred from one side beam to another, and there is room for improvement.

[0008] [Existing Technical Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. 2020-055473. Summary of the Invention

[0009] [The technical problem the invention aims to solve] In view of the above-mentioned problems, the present invention aims to provide a lower body structure for a vehicle that ensures the desired lateral collision performance even when the floor panel is attached to the upper side of the side beam at the center position in the vertical direction of the vehicle.

[0010] Technical means to solve technical problems This invention relates to a lower body structure of a vehicle, comprising a pair of left and right side beams extending along the longitudinal direction of the vehicle at both ends of the floor panel in the vehicle width direction, and a floor crossbeam extending along the vehicle width direction and connecting the pair of left and right side beams. Each side beam has an upper surface facing upwards towards the vehicle and forms a closed section in the longitudinal section along the vehicle width direction. The floor crossbeam comprises an upper beam fixed to the upper surface of the floor panel (which is the upper surface of the floor panel), an upper beam protruding upwards towards the vehicle and having an upper surface facing upwards towards the vehicle, and a lower beam fixed to the lower surface of the floor panel (which is the lower surface of the floor panel) and protruding downwards towards the vehicle. The side beams and the floor crossbeam are joined such that the upper surfaces of the side beams and the upper surfaces of the crossbeams are aligned in the vertical direction of the vehicle. The floor panel, the upper beam, and the lower beam, disposed between the upper beam and the lower beam, form a closed section in the longitudinal section along the longitudinal direction of the vehicle.

[0011] The two ends of the floor crossbeam that extends along the width of the vehicle and connects the left and right pairs of side beams can be directly connected to the side beams, or they can be connected via seat mounting brackets or connecting plates located at both ends.

[0012] Furthermore, the aforementioned side beam and floor crossbeam can be joined by aligning the upper surfaces of the side beam and the crossbeam in the vertical direction of the vehicle. This can be either a side-by-side joining of the upper surfaces of the side beam and the crossbeam in the vehicle width direction, or a joining where a portion of the upper surface of the crossbeam overlaps with the upper surface of the side beam. Moreover, if the upper surface of the side beam is an inclined surface relative to the vehicle width direction in the vertical direction of the vehicle, this refers to the upper surface of the crossbeam being positioned from the upper end to the lower end of the inclined upper surface of the side beam in the vertical direction of the vehicle.

[0013] With this invention, even if the floor panel is attached to the upper side of the side beam at the center position in the vertical direction of the vehicle, the desired side impact performance can be ensured.

[0014] Specifically, the lower body structure of the vehicle includes a pair of left and right side beams extending along the longitudinal direction of the vehicle at both ends of the floor panel in the vehicle width direction, and a floor crossbeam extending along the vehicle width direction and connecting the pair of left and right side beams. The side beams have an upper surface facing upwards towards the vehicle and form a closed section in the longitudinal section along the vehicle width direction (hereinafter referred to as the width direction longitudinal section).

[0015] The floor beam has an upper beam fixed to the upper surface of the floor panel, which is the upper surface of the floor panel, an upper beam that protrudes upward toward the vehicle and has a beam that faces upward toward the vehicle, and a lower beam fixed to the lower surface of the floor panel, which is the lower surface of the floor panel and protrudes downward toward the vehicle.

[0016] Furthermore, the side beams and the floor crossbeams are joined such that the upper surfaces of the side beams and the upper surfaces of the crossbeams are aligned in the vertical direction of the vehicle. Additionally, the ridge portions extending along the longitudinal direction of the vehicle on the upper surface of the side beams and the ridge portions extending along the width direction on the upper surface of the floor crossbeams are respectively more rigid than other parts of their respective components. Thus, the ridge portions with higher rigidity in their respective components are approximately orthogonal in their respective extension directions in a top view, but are located at approximately the same position in the vertical direction of the vehicle. That is, the ridge portions of the floor crossbeams and the ridge portions of the side beams are continuous. Therefore, the lower body structure of the vehicle can efficiently transfer lateral collision loads from one side beam to the other.

[0017] Furthermore, the floor panel, the upper beam, and the lower beam disposed between the upper beam and the lower beam form a closed section in the longitudinal section along the longitudinal direction. Therefore, compared to the cross-sectional area of ​​the floor beam consisting solely of the upper beam fixed to the upper surface of the floor panel, the cross-sectional area of ​​the floor beam that functions as a load-transferring member in the vehicle width direction, transmitting lateral collision loads from one side beam to the other, is increased in the longitudinal section along the vehicle's longitudinal direction.

[0018] Therefore, the floor beam, which functions as a transfer member for transmitting lateral impact loads from one side beam to the other, has increased cross-sectional strength in its longitudinal section along the vehicle's longitudinal direction, enabling efficient transmission of lateral impact loads from one side beam to the other. Thus, in the lower body structure of the vehicle where the floor panel joins the side beam at its upper side at the central position in the vertical direction of the vehicle, the desired lateral impact performance can be ensured.

[0019] As an embodiment of the present invention, the upper beam may also have a ridge portion extending along the vehicle width direction as an upper beam ridge portion, and the upper beam has three or more upper beam ridge portions arranged at intervals in the vehicle front-rear direction.

[0020] With this invention, there are more than three upper ridge sections in the upper beam that have higher rigidity than other parts, thus further increasing the cross-sectional strength of the upper beam.

[0021] Therefore, the cross-sectional strength of the floor beam, which has a closed cross-section formed by the upper beam (which has a further increased cross-sectional strength) and the lower beam separated by the floor panel, can be further increased. Therefore, the lower body structure of the vehicle can improve its function as a load-transferring member in the vehicle width direction.

[0022] Alternatively, as an embodiment of the present invention, the lower beam may have a ridge portion extending along the vehicle width direction as a lower beam ridge portion, and the lower beam may have three or more lower beam ridge portions arranged at intervals in the vehicle's longitudinal direction.

[0023] With this invention, there are more than three lower ridge sections in the lower beam that have higher rigidity than other parts, thus further increasing the cross-sectional strength of the lower beam.

[0024] Therefore, the cross-sectional strength of the floor beam, which forms a closed cross-section via the floor panel and whose cross-sectional strength has been further increased by the upper and lower beams, can be further enhanced. Thus, the lower body structure of the vehicle can further improve its function as a load-transferring member in the vehicle width direction.

[0025] Alternatively, as an embodiment of the present invention, the floor beam may have a main body portion consisting of joint portions located at both ends in the vehicle width direction and engaging with the side beams, and joint portions on both sides in the vehicle width direction. The upper beam constituting the main body portion has an upwardly projecting portion protruding above the vehicle and spaced apart in the vehicle's longitudinal direction, having an upwardly convex portion on the upper surface of the beam and an upwardly concave portion connecting each of the upwardly convex portions in the vehicle's longitudinal direction, positioned below the vehicle's upper surface than the upper surface of the beam. In the longitudinal section in the longitudinal direction, the upper beam constituting the main body portion is connected by the spaced-apart... The upper convex portion and the upper concave portion are formed into an approximately M-shaped cross section. The lower beam constituting the main body has lower convex portions that protrude downwards from the vehicle and are spaced apart in the longitudinal direction of the vehicle, and lower concave portions that connect each of the lower convex portions in the longitudinal direction of the vehicle and are positioned above the vehicle above the lower end of the lower convex portions. In the longitudinal section along the longitudinal direction of the vehicle, the lower beam constituting the main body is formed into an approximately inverted M-shaped cross section by the spaced lower convex portions and the lower concave portions. The upper beam and the lower beam are joined by the upper concave portions and the lower concave portions.

[0026] The joint portions located at both ends in the vehicle width direction and engaging with the side beams may be part of the floor crossbeam that is continuous with the main body, or they may be seat mounting brackets or connecting plates located at both ends.

[0027] The present invention further increases the cross-sectional strength of the floor beam. Specifically, the floor beam has a main body portion consisting of joint portions located at both ends in the vehicle width direction and engaging with the side beams, and joint portions on both sides in the vehicle width direction. The upper beam constituting the main body portion has an upwardly projecting portion protruding above the vehicle and spaced apart in the vehicle's longitudinal direction, having an upwardly convex portion with an upper surface, and an upwardly concave portion connecting each of the upwardly convex portions in the vehicle's longitudinal direction and positioned below the vehicle's upper surface. In the longitudinal section in the longitudinal direction, the upper beam constituting the main body portion is formed into an approximately M-shaped cross-section by the spaced-apart upwardly convex and concave portions. Therefore, at least six upwardly extending upper ridges spaced apart in the vehicle's longitudinal direction are formed in the upper beam along the vehicle width direction. This results in an upper beam with low height and high cross-sectional strength in the vertical direction of the vehicle.

[0028] Furthermore, the lower beam constituting the main body has convex portions protruding downwards from the vehicle and spaced apart in the vehicle's longitudinal direction, and concave portions connecting each convex portion in the vehicle's longitudinal direction, positioned above the vehicle and concave relative to the lower end of the convex portions. In the longitudinal section in the longitudinal direction, the lower beam constituting the main body is formed into an approximately inverted M-shaped cross-section by the spaced-apart convex and concave portions. Therefore, at least six lower ridges extending along the vehicle width direction are formed in the lower beam at intervals in the vehicle's longitudinal direction. This allows for the construction of a lower beam with low vertical height and high cross-sectional strength.

[0029] Furthermore, the upper beam and the lower beam are joined by the upper concave portion and the lower concave portion. Thus, in the floor beam forming a closed cross-section via the floor panel, closed cross-sections can be formed by the upper convex portion and the lower convex portion spaced at a predetermined interval in the vehicle's longitudinal direction. Therefore, in the floor beam formed by the upper beam and the lower beam, two closed cross-sections can be formed, further improving the cross-sectional strength of the floor beam. Therefore, the lower body structure of the vehicle can further enhance its function as a load-bearing member in the vehicle width direction.

[0030] Alternatively, as an embodiment of the present invention, a floor protrusion may be provided on the floor panel, the floor protrusion extending along the vehicle width direction and protruding in any direction in the vertical direction of the vehicle, the upper concave portion, the floor protrusion, and the lower concave portion being stacked in the vertical direction of the vehicle, and the upper beam and the lower beam being joined via the floor protrusion through the upper concave portion and the lower concave portion.

[0031] The aforementioned floor protrusion that protrudes in either the vertical direction of the vehicle can protrude upwards or downwards from the vehicle.

[0032] According to the present invention, a convex portion of the floor is disposed on the floor panel, extends along the vehicle width direction, and protrudes in any direction in the vertical direction of the vehicle. The upper concave portion, the convex portion of the floor, and the lower concave portion are stacked in the vertical direction of the vehicle, and the upper beam and the lower beam are joined through the convex portion of the floor and the upper and lower concave portions.

[0033] Therefore, compared to a floor beam with a closed cross section formed by sandwiching the upper concave portion and the lower concave portion between the flat floor panel, this structure can control the protrusion height of the upper or lower convex portion on the opposite side of the protrusion direction of the floor convex portion relative to the floor panel to be very low, and ensure the cross section height of the floor beam forming the closed cross section.

[0034] Therefore, the cross-sectional strength of the floor beam, composed of the upper beam and the lower beam, can be further improved. Consequently, the lower body structure of the vehicle can further enhance its function as a load-transferring component in the vehicle width direction.

[0035] Alternatively, as a variant of the present invention, the upper beam and the lower beam may be provided with flange portions that protrude along the vehicle width direction and in the front-rear direction of the vehicle, and the upper beam and the lower beam are joined to the floor panel through the flange portions.

[0036] This invention allows the upper beam and the lower beam to be securely fixed to the floor panel via the flange. Therefore, the floor beam sandwiched between the upper and lower beams effectively forms a closed cross section.

[0037] Alternatively, as an embodiment of the present invention, a plurality of reinforcing ribs extending in the front-rear direction of the vehicle may be formed at intervals in the flange portion formed along the vehicle width direction.

[0038] The present invention can improve the shape retention of the flange portion that is longer in the vehicle width direction.

[0039] Therefore, the shape retention of the upper beam and the lower beam having the flange portion can be improved.

[0040] Alternatively, as an embodiment of the present invention, the floor beam may include a first floor beam disposed at approximately the center of the floor panel in the vehicle longitudinal direction and a second floor beam disposed at a predetermined interval behind the first floor beam.

[0041] This invention enables the installation of two floor beams at predetermined intervals in the longitudinal direction of a vehicle, forming a closed cross-section that sandwiches the floor panel. Therefore, the performance of the floor beams in transmitting collision loads during a lateral collision in the vehicle width direction can be improved.

[0042] Therefore, in the lower body structure of the vehicle where the floor panel is joined to the side beam at the upper side of the central position in the vertical direction of the vehicle, the desired side impact performance can be ensured.

[0043] [Invention Effects] The present invention provides a lower body structure for a vehicle that ensures desired lateral collision performance even when the floor panel is attached to the upper side of the side beam at the center position in the vertical direction of the vehicle. Attached Figure Description

[0044] Figure 1 This is a perspective view of the lower part of the vehicle body from the front, showing its exterior appearance. Figure 2 This is a plan view of the lower body of the vehicle as seen from a top view. Figure 3 This is a plan view of the lower body of the vehicle as seen from below. Figure 4 For along Figure 2 Enlarged view of the main part of the cross section in the direction of arrow A-A; Figure 5 For along Figure 2 Enlarged view of the main part of the cross section in the direction of arrow B-B in the image; Figure 6 For along Figure 2 Enlarged view of the main part of the cross section in the C-C arrow direction view; Figure 7 For along Figure 2 Enlarged view of the main part of the cross section in the D-D arrow direction view; Figure 8 This is a schematic cross-sectional view of the reinforcing ribs formed in the concave and convex portions, viewed from the front and rear directions of the vehicle. Detailed Implementation

[0045] With the following appendix Figure 1 This invention will now be described as an embodiment of the present invention.

[0046] In this embodiment, the vehicle 1 is, for example, an electric vehicle, whose front floor panel 4 is attached to the upper side of the side beam 3 at the center position in the vertical direction of the vehicle. Figures 1 to 8 The lower body structure of the cabin section of this vehicle 1 is described in detail.

[0047] Figure 1 This is a perspective view of the lower part of vehicle 1 from the front. Figure 2 This is a plan view of the lower body of vehicle 1. Figure 3 This is a bottom view of the lower body of vehicle 1. Figure 4 It is along Figure 2 Enlarged cross-sectional view of the main part in the A-A arrow direction view. Figure 5 It is along Figure 2 An enlarged cross-sectional view of the main part in the B-B arrow direction view. Figure 6 It is along Figure 2 An enlarged cross-sectional view of the main part in the C-C arrow direction view. Figure 7 It is along Figure 2 An enlarged cross-sectional view of the main part in the D-D arrow direction view. Figure 8 This is a schematic cross-sectional view of the reinforcing ribs 66 formed in the concave portions 72 and 82 and the flange portion 65, viewed from the front and rear directions of the vehicle.

[0048] In detail, Figure 4 Is Figure 2 In the A-A direction view extending along the front-rear direction of the vehicle, an enlarged cross section view of the portion where the first floor crossbeam 6A and the second floor crossbeam 6B are arranged is shown, and the side beam 3 and the front seat bracket 62 are shown in dashed lines.

[0049] Figure 5 Is Figure 2 In the B-B direction view extending along the vehicle width direction, the enlarged cross section view near the side beam 3 on the right side in the vehicle width direction, and the first floor crossbeam 6A is shown in dashed line. Figure 6 Is Figure 2 In the C-C arrow view extending along the vehicle width direction, enlarged cross-sectional views of the two ends and the central part in the vehicle width direction are shown, and the first floor beam 6A is shown with a dashed line. Figure 7 Is Figure 2 Enlarged cross-sectional views of the two ends and the central part in the vehicle width direction in the D-D arrow direction view extending along the vehicle width direction.

[0050] In the diagram, arrows Fr and Rr indicate the forward and backward directions, with Fr indicating the front and Rr indicating the rear. Arrows Rw and Lw indicate the width of the vehicle, with Rw indicating the rightward direction and Lw indicating the leftward direction. Furthermore, arrows Uh and Dh indicate the vertical direction of the vehicle, with Uh indicating the top of the vehicle and Dh indicating the bottom.

[0051] like Figure 1 and Figure 2 As shown, the lower body of vehicle 1 includes: a front bulkhead 2 that separates the engine compartment and the passenger compartment in the longitudinal direction of the vehicle; a pair of left and right side beams 3 that extend from the lower part of both ends of the front bulkhead 2 in the width direction along the rear of the vehicle; and a front floor panel 4 disposed between the left and right side beams 3 and forming the passenger compartment floor.

[0052] like Figure 1 and Figure 2 As shown, in the front floor panel 4, a passage 5 is formed approximately in the center of the vehicle width direction. The passage 5 extends from the front of the vehicle along the rear of the vehicle and is generally convex in the shape of a passage. Figure 1 and Figure 2 As shown, in the lower part of the vehicle body 1, a floor crossbeam 6 connecting the left and right paired side beams 3 in the vehicle width direction is fixed to the front floor panel 4. A battery unit (not shown) is provided on the lower side of the front floor panel 4.

[0053] In addition, in the lower body of vehicle 1, the floor crossbeam 6, which connects the left and right side beams 3 in the vehicle width direction, includes a first floor crossbeam 6A and a second floor crossbeam 6B. The first floor crossbeam 6A is located approximately at the center of the front floor panel 4 in the vehicle longitudinal direction, and the second floor crossbeam 6B is located at the rear of the vehicle at a predetermined interval relative to the first floor crossbeam 6A.

[0054] The following details each structure.

[0055] The front bulkhead 2 is a plate member with thickness in the longitudinal direction of the vehicle, and its lower part is curved towards the rear of the vehicle. The front floor panel 4 is provided from the lower end of the front bulkhead 2 towards the rear of the vehicle.

[0056] The side beam 3 extends from the lower ends of both ends of the front bulkhead 2 in the vehicle width direction to the rear of the vehicle and is formed in pairs on the left and right. The cross-sectional shape of its longitudinal section along the vehicle width direction (hereinafter referred to as the longitudinal section in the width direction) forms a closed section with a roughly rectangular cross-section.

[0057] More specifically, in the longitudinal section of the width direction, the side beam 3 comprises an outer side beam 3a with a roughly hat-shaped cross-section protruding outward in the vehicle width direction and an inner side beam 3b with a roughly hat-shaped cross-section protruding inward in the vehicle width direction, and has a roughly rectangular shape that is slightly longer than the vehicle width direction in the vertical direction of the vehicle. The upper surface of the side beam 3, which has a roughly rectangular shape in the longitudinal section of the vehicle width direction, is designated as the upper surface 3c of the side beam. The surface of the side beam 3 along the vertical direction of the vehicle is designated as the side surface 3d, and a side beam ridge portion 3e is formed at the corner between the upper surface 3c and the side surface 3d.

[0058] like Figures 1 to 5 As shown, the front floor panel 4 is a generally flat plate member with thickness in the vertical direction of the vehicle. Its front end is connected to the lower end of the front bulkhead 2. The front of the front floor panel 4 is inclined towards the front bulkhead 2 and towards the upper part of the vehicle.

[0059] The surface of the front floor panel 4 facing upwards towards the vehicle is designated as the upper surface 4a of the floor panel, and the surface facing downwards towards the vehicle is designated as the lower surface 4b of the floor panel.

[0060] A passage 5, which will be described later, protrudes upward toward the vehicle, is formed approximately in the center of the front floor panel 4 in the vehicle width direction.

[0061] The front end of the passage section 5 is joined to the front bulkhead 2, and its rear end forms at the front of the first floor beam 6A, which will be described later.

[0062] Furthermore, floor protrusions 4c that convex upwards are formed at two locations in the front floor panel 4: approximately at the center of the vehicle's longitudinal direction and at a predetermined interval further rear of the vehicle (see reference). Figure 4 ).

[0063] Additionally, at both ends of the front floor panel 4 in the vehicle width direction, there are joining pieces 4d that bend upwards towards the vehicle and engage with the side surface 3d of the side beam 3.

[0064] like Figures 5 to 7 As shown, the front floor panel 4, constructed as described above, has its joining piece 4d abutting against and fixed to the side 3d of the side beam 3, which is approximately rectangular in shape and slightly longer in the vertical direction than in the width direction of the vehicle, on the inner side 3d of the side beam 3 in the width direction. At this time, the floor panel 4 is fixed to the side beam 3, which is approximately rectangular in shape and slightly longer in the vertical direction than in the width direction of the vehicle, and is located above the vehicle, closer to the center position in the vertical direction.

[0065] The floor crossbeam 6 includes seat brackets 622 and 64 at both ends in the vehicle width direction that engage with the side beams 3, and a main body portion 60 forming between each seat bracket 622 and 64, and connecting the left and right side beams 3 in the vehicle width direction. The main body portion 60 of the floor crossbeam 6 has a plurality of crossbeam ridges 61 extending in the vehicle width direction.

[0066] The main body 60 of the floor beam 6 has an upper beam 70 fixed to the upper surface 4a of the floor panel of the front floor panel 4, which has an approximately M-shaped cross section extending in the vehicle width direction, and a lower beam 80 fixed to the lower surface 4b of the floor panel of the front floor panel 4, which has an approximately inverted M-shaped cross section extending in the vehicle width direction. The upper beam 70 and the lower beam 80 sandwich the front floor panel 4 from the vertical direction of the vehicle to form the main body 60 of the floor beam 6.

[0067] like Figure 4 As shown, the upper beam 70, which has an approximately M-shaped cross section, has a plurality of upper beam ridges 70a that are formed by the upper beam ridges 61, which are spaced at a predetermined interval in the longitudinal direction of the vehicle and extend along the vehicle width direction. In the longitudinal section in the longitudinal direction, the upper beam 70 has an approximately inverted concave shape with an open section under the vehicle.

[0068] More specifically, the upper beam 70 has the following features in its longitudinal section in the front-rear direction: an upper convex portion 71 that is arranged at predetermined intervals in the front-rear direction of the vehicle and protrudes upwards towards the vehicle; an upper concave portion 72 that is arranged between the upper convex portions 71 and disposed below the vehicle relative to the upper surface 711 of the upper convex portions 71; and a flange portion 65 that protrudes from the lower end of the outer side surface 712 of the upper convex portion 71 in the front-rear direction of the vehicle.

[0069] The convex portion 71 has, in its longitudinal section in the front-rear direction, a generally horizontal upper surface 711 of a crossbeam, an outer side 712 extending outward and downward from the outer side of the upper surface 711 in the front-rear direction, and an inner side 713 extending inward and downward from the inner side of the upper surface 711 in the front-rear direction. A flange portion 65, fixed to the upper surface 4a of the floor panel 4, is also provided at the lower end of the outer side 712.

[0070] In the longitudinal section along the front-rear direction, the inclined length of the inner surface 713 is shorter than that of the outer surface 712. Specifically, in the section along the front-rear direction, the length of the inner surface 713 is about half that of the outer surface 712.

[0071] The upper concave portion 72 is formed approximately horizontally in the longitudinal section in the longitudinal direction, and connects the lower ends of the inner side surfaces 713 of the concave portions 71 located on both sides of the vehicle in the longitudinal direction. Therefore, the upper concave portion 72 is positioned below the vehicle and above the vehicle, compared to the upper surface 711 of the upper convex portion 71.

[0072] like Figure 2 As shown, in the concave portions 72 and flange portions 65 formed between the convex portions 71, a plurality of reinforcing ribs 66 are formed at intervals in the vehicle width direction, protruding upwards from the vehicle and extending along the vehicle's longitudinal direction (see reference). Figure 8 Specifically, the reinforcing rib 66 is formed in the flange portion 65 extending in the vehicle width direction, covering a range of approximately one-third on both sides in the vehicle width direction. Furthermore, the reinforcing rib 66 is also formed in small quantities in the concave portion 72 extending in the vehicle width direction, covering a range of approximately one-third on both sides and in the central portion.

[0073] As described above, the upper beam 70 has upper beam ridge portions 70a (crossbeam ridge portions 61) extending in the vehicle width direction at the corners of the upper surface 711 and the outer side surface 712, the corners of the upper surface 711 and the inner side surface 713, the corners of the outer side surface 712 and the flange portion 65, and the corners of the inner side surface 713 and the upper concave portion 72. The upper beam 70 is generally M-shaped when viewed from the vehicle width direction.

[0074] like Figure 4 As shown, the lower beam 80, which has an approximately inverted M-shaped cross section, has a plurality of lower beam ridge sections 80a that are formed by the cross beam ridge sections 61, which are spaced at a predetermined interval in the longitudinal direction of the vehicle. In the longitudinal section in the longitudinal direction, the lower beam 80 has an approximately concave shape with an open section above the vehicle.

[0075] More specifically, in the longitudinal section in the front-rear direction, the lower side beam 80 includes: a convex portion 81 that is arranged at predetermined intervals in the front-rear direction of the vehicle and protrudes in the downward direction of the vehicle; a concave portion 82 that is arranged between the convex portions 81 and positioned above the vehicle relative to the bottom surface 811 of the crossbeam of the convex portion 81; and a flange portion 65 that protrudes from the upper end of the outer side surface 812 of the convex portion 81 in the front-rear direction of the vehicle.

[0076] The lower convex portion 81 has, in its longitudinal section in the longitudinal direction, a generally horizontal crossbeam bottom surface 811, an outer side surface 812 extending outward from the outer side of the crossbeam bottom surface 811 in the longitudinal direction towards the upper outer side of the vehicle, and an inner side surface 813 extending inward from the inner side of the crossbeam bottom surface 811 in the longitudinal direction towards the upper inner side of the vehicle. A flange portion 65 is also provided at the upper end of the outer side surface 812, which is fixed to the lower surface 4b of the floor panel of the front floor panel 4.

[0077] In the front-to-back cross-section, the inclined length of the inner surface 813 is longer than that of the outer surface 812. Specifically, in the front-to-back cross-section, the length of the inner surface 813 is twice that of the outer surface 812.

[0078] The concave portion 82 is approximately horizontal in the longitudinal section in the longitudinal direction and connects to the upper ends of the inner side surfaces 813 of the concave portions 81 located on both sides of the vehicle in the longitudinal direction. Therefore, the concave portion 82 is positioned above the vehicle and above the flange portion 65, compared to the bottom surface 811 of the lower convex portion 81.

[0079] like Figure 3 As shown, in the concave portions 82 and flange portions 65 formed between the lower convex portions 81, a plurality of reinforcing ribs 66 are formed at intervals in the vehicle width direction, protruding downwards from the vehicle and extending in the vehicle longitudinal direction (see reference). Figure 8 Specifically, the reinforcing rib 66 is formed in the flange portion 65 extending in the vehicle width direction, except for the central quarter portion in the vehicle width direction. Furthermore, the reinforcing rib 66 is formed in the recessed portion 82 extending in the vehicle width direction, covering the entire range in the vehicle width direction.

[0080] As described above, the lower beam 80 has lower beam ridge portions 80a (crossbeam ridge portions 61) extending in the vehicle width direction at the corners of the bottom surface 811 and the outer side surface 812 of the crossbeam, the corners of the bottom surface 811 and the inner side surface 813 of the crossbeam, the corners of the outer side surface 812 and the flange portion 65, and the corners of the inner side surface 813 and the concave portion 82. The lower beam 80 is generally inverted M shape when viewed from the vehicle width direction.

[0081] Regarding the upper beam 70 and lower beam 80 formed as described above, the upper beam 70 is positioned above the front floor panel 4 on the vehicle, and the lower beam 80 is positioned below the front floor panel 4 on the vehicle and corresponds to the upper beam 70 in the vertical direction of the vehicle. That is, the upper beam 70 and lower beam 80 are configured and fixed such that the upper beam 70 and lower beam 80 sandwich the front floor panel 4 from both sides in the vertical direction of the vehicle, forming the floor crossbeam 6.

[0082] In detail, such as Figure 4 As shown, an upper beam 70 and a lower beam 80 are configured such that the upper concave portion 72 and the lower concave portion 82 are located in the floor convex portion 4c that extends in the vehicle width direction and protrudes upward in the front floor panel 4.

[0083] Then, the flange portion 65 of the upper beam 70 disposed on the upper surface 4a of the floor panel of the front floor panel 4 and the flange portion 65 of the lower beam 80 disposed on the lower surface 4b of the floor panel of the front floor panel 4 are joined together in a manner that clamps the front floor panel 4. At this time, the upper concave portion 72 of the upper beam 70, the floor convex portion 4c of the front floor panel 4, and the lower concave portion 82 of the lower beam 80 are stacked in the vertical direction of the vehicle. The stacked upper concave portion 72 of the upper beam 70 and the lower concave portion 82 of the lower beam 80 are joined together with the floor convex portion 4c of the front floor panel 4.

[0084] Thus, the front floor panel 4, the upper beam 70, and the lower beam 80 are fixed, forming a floor beam 6 that clamps the front floor panel 4 to form a closed cross section. Specifically, a closed cross section is formed when the front floor panel 4 is clamped from the vertical direction of the vehicle by the upper convex portion 71 and the lower convex portion 81 on one side of the vehicle's longitudinal direction, and a closed cross section is formed when the front floor panel 4 is clamped from the vertical direction of the vehicle by the upper convex portion 71 and the lower convex portion 81 on the other side of the vehicle's longitudinal direction. That is, the upper concave portion 72, the floor convex portion 4c, and the lower concave portion 82, which are stacked and fixed in the vertical direction of the vehicle, form a closed cross section formed by the upper convex portion 71 and the lower convex portion 81 on both sides of the vehicle's longitudinal direction.

[0085] like Figure 4 As shown, in the longitudinal section in the front-rear direction, the distance between the front floor panel 4 and the bottom surface 811 of the crossbeam in the vertical direction of the vehicle is smaller than the distance between the front floor panel 4 and the upper surface 711 of the crossbeam in the vertical direction of the vehicle. That is, compared to the height of the floor crossbeam 6 protruding from the upper surface 4a of the floor panel 4 of the front floor panel 4 upwards towards the vehicle, the height of the floor crossbeam 6 protruding from the lower surface 4b of the floor panel 6 downwards towards the vehicle is lower. However, the floor convex portion 4c, which is stacked with the upper concave portion 72 and the lower concave portion 82, is located above the vehicle relative to other parts of the front floor panel 4. Therefore, in the front-rear direction of the vehicle, the floor convex portion 4c is positioned approximately at the center of the upper surface 711 and the bottom surface 811 of the crossbeam.

[0086] In other words, the present invention is in the following form: the closed section of the floor beam 6, which is formed by the upper convex portion 71 and the lower convex portion 81 sandwiching the front floor panel 4, is located above the vehicle than the front floor panel 4, but protrudes to the same extent on both sides in the vertical direction of the vehicle relative to the floor convex portion 4c of the stacked upper concave portion 72 and lower concave portion 82 located at the center of the floor beam 6 in the vertical direction of the vehicle.

[0087] Furthermore, in the main body 60, the flanges 65 of the upper beam 70 and lower beam 80 are spaced apart from the front floor panel 4 in the vehicle's longitudinal direction, with the upper concave portion 72 and the lower concave portion 82 spaced apart from the floor convex portion 4c. The floor convex portion 4c protrudes upwards from the front floor panel 4, therefore, in the vehicle's vertical direction, the joints of the upper concave portion 72 and the lower concave portion 82 with the floor convex portion 4c are located higher on the vehicle than the joints of the flanges 65 of the upper beam 70 and lower beam 80 spaced apart from the front floor panel 4.

[0088] The cross-sectional strength of these joints in the longitudinal section of the main body 60 is lower than that of other parts. Therefore, assuming that in the main body 60 of the floor beam 6, the joints between the upper concave portion 72 and the lower concave portion 82 and the floor convex portion 4c in the vertical direction of the vehicle, and the joints between the flange portions 65 of the upper beam 70 and the lower beam 80 and the front floor panel 4, which are spaced apart in the longitudinal direction of the vehicle, are aligned in a straight line in the longitudinal direction of the vehicle, compared with this case, by arranging the joints between the upper concave portion 72 and the lower concave portion 82 and the floor convex portion 4c above the vehicle, a floor beam 6 with high cross-sectional strength can be formed.

[0089] In addition, the upper convex portion 71 of the upper beam 70 is fixed to the upper surface 4a of the floor panel of the front floor panel 4. The upper surface 4a of the floor panel of the front floor panel 4 is fixed to the side beam 3, which is approximately rectangular in shape and slightly longer in the vertical direction than in the width direction of the vehicle, and is located above the vehicle than the center position in the vertical direction of the vehicle. However, the upper surface 3c of the side beam 3 and the upper surface 711 of the crossbeam of the upper convex portion 71 are formed at the same height in the vertical direction of the vehicle.

[0090] As described above, the floor crossbeam 6, which forms a closed section by the upper beam 70 and the lower beam 80, has a first floor crossbeam 6A located near the center of the front floor panel 4 in the vehicle longitudinal direction and a second floor crossbeam 6B located at a predetermined interval relative to the first floor crossbeam 6A at the rear of the vehicle.

[0091] In the floor crossbeam 6, the first floor crossbeam 6A at the front of the vehicle is equipped with a front seat bracket 62. The front seat bracket 62 has a front inner seat bracket 621 located at the center of the first floor crossbeam 6A in the vehicle width direction and front outer seat brackets 622 located on both outer sides.

[0092] The front inner seat bracket 621 is an open, roughly box-shaped section that extends beyond the vehicle width, used to mount the front seat on its upper surface in the front center of the vehicle. The front inner seat bracket 621 is secured to the first floor crossbeam 6A by welding, such as spot welding.

[0093] The front outer seat bracket 622 is positioned on both sides of the first floor crossbeam 6A in the vehicle width direction, and is used to mount the front seat on the upper surface of the vehicle's front outer portion in the vehicle width direction. The front outer seat bracket 622 is roughly mountain-shaped when viewed from the front-rear direction of the vehicle, and is a roughly box-shaped opening at the bottom of the vehicle. It has flange portions 623 (623a, 623b) extending in the vehicle width direction on both sides. The front outer seat bracket 622 has a ridge portion at the upper part (see reference). Figure 4 ).

[0094] Specifically, the inner flange 623a of the front outer seat bracket 622, which is roughly mountain-shaped when viewed from the front-rear direction of the vehicle, is engaged and fixed to the upper surface 711 of the upper beam 70 that constitutes the first floor beam 6A.

[0095] The outer flange 623b of the front outer seat bracket 622, which is roughly mountain-shaped when viewed from the front and rear of the vehicle, is joined and fixed to the upper surface 3c of the side beam 3 in the vehicle width direction.

[0096] Thus, the first floor crossbeam 6A is connected to the side beam 3 via the front outer seat bracket 622, which has an inner flange 623a that is engaged and fixed to the upper surface 711 of the upper beam 70 and an outer flange 623b that is engaged and fixed to the upper surface 3c of the side beam 3.

[0097] The second floor crossbeam 6B at the rear of the vehicle in the floor crossbeam 6 includes a rear outer seat bracket 64. The rear outer seat bracket 64 is positioned on both outer sides of the second floor crossbeam 6B in the vehicle width direction. The rear outer seat bracket 64 is positioned on both sides of the second floor crossbeam 6B in the vehicle width direction for mounting the front seat on its upper surface, on the outer portion of the rear of the vehicle in the vehicle width direction. The illustration of the rear inner seat bracket on the inner portion of the rear of the vehicle in the vehicle width direction where the front seat is mounted is omitted.

[0098] The rear outer seat bracket 64 has a main body 641 that is approximately square in plan view and is fixed to the upper convex portion 71 of the upper beam 70 that constitutes the second floor crossbeam 6B, and a flange portion 642 that extends outward from the main body 641 in the vehicle width direction.

[0099] The rear outer seat bracket 64 has a ridged section on the upper part (see reference). Figure 4 ).

[0100] The main body 641 is fixed to the second floor beam 6B by welding such as spot welding, and the flange 642 is fixed to the upper surface 3c of the side beam 3.

[0101] Thus, the second floor crossbeam 6B is connected to the side beam 3 via the rear outer seat bracket 64, which has a main body portion 641 that is engaged and fixed to the upper surface 711 of the upper beam 70 and a flange portion 642 that is engaged and fixed to the upper surface 3c of the side beam 3.

[0102] As described above, the first floor crossbeam 6A, which is connected to the side beam 3 via the front outer seat bracket 622, and the second floor crossbeam 6B, which is connected to the side beam 3 via the rear outer seat bracket 64, are located at approximately the same position in the vertical direction of the vehicle as the upper surface 711 of the upper beam 70 and the upper surface 3c of the side beam 3.

[0103] Therefore, the upper beam ridge 70a (beam ridge 61) extending in the vehicle width direction in the first floor beam 6A and the second floor beam 6B is continuous with the ridge of the front outer seat bracket 622, the ridge of the rear outer seat bracket 64, and the side beam ridge 3e formed at the corner of the upper surface 3c and the side surface 3d of the side beam 3.

[0104] More specifically, the floor crossbeam 6 (6A, 6B) is connected to the upper surface 3c of the side beam of the side beam 3 via the front outer seat bracket 622 and the rear outer seat bracket 64. The upper beam ridge 70a (crossbeam ridge 61) formed on both sides of the upper convex portion 71 of the upper beam 70 constituting the floor crossbeam 6 (6A, 6B) in the vehicle longitudinal direction and the side beam ridge 3e formed at the corner of the upper surface 3c and the side surface 3d in the side beam 3 have different extension directions and are separated by the front outer seat bracket 622 and the rear outer seat bracket 64, but they are in approximately the same position in the vehicle vertical direction and are continuous via the front outer seat bracket 622 and the rear outer seat bracket 64.

[0105] As described above, the lower body structure of vehicle 1 includes a pair of left and right side beams 3 extending along the vehicle longitudinal direction at both ends of the front floor panel 4 in the vehicle width direction, and a floor crossbeam 6 extending along the vehicle width direction and connecting the pair of left and right side beams 3. The side beams 3 have a side beam upper surface 3c facing upwards of the vehicle and forming a closed section in the longitudinal section along the vehicle width direction. The floor crossbeam 6 has an upper beam 70 fixed to the upper surface of the floor panel 4a, which is the upper surface of the front floor panel 4, a crossbeam upper surface 711 protruding upwards of the vehicle and facing upwards of the vehicle, and a lower beam 80 fixed to the lower surface of the floor panel 4b, which is the lower surface of the front floor panel 4 and protruding downwards of the vehicle. The side beams 3 and the floor crossbeam 6 are joined in such a way that the upper surface of the side beams 3c and the upper surface of the crossbeams 711 are aligned in the vertical direction of the vehicle. The front floor panel 4, the upper beam 70 and the lower beam 80, which are arranged between the upper beam 70 and the lower beam 80, form a closed section in the longitudinal section along the vehicle longitudinal direction.

[0106] This structure ensures the desired side impact performance even though the front floor panel 4 is attached to the upper side of the side beam 3 at the center position in the vertical direction of the vehicle.

[0107] Specifically, the lower body structure of vehicle 1 includes a pair of left and right side beams 3 extending along the longitudinal direction of the vehicle at both ends of the front floor panel 4 in the vehicle width direction, and a floor crossbeam 6 extending along the vehicle width direction and connecting the pair of left and right side beams 3. The side beams 3 have an upper surface 3c facing upwards of the vehicle and form a closed section in the longitudinal section in the width direction.

[0108] In addition, the floor beam 6 has an upper beam 70 that is fixed to the upper surface of the floor panel 4a, which is the upper surface of the front floor panel 4, protruding upward toward the vehicle and having a beam upper surface 711 facing upward toward the vehicle, and a lower beam 80 that is fixed to the lower surface of the floor panel 4b, which is the lower surface of the front floor panel 4, and protruding downward toward the vehicle.

[0109] Furthermore, the side beam 3 and the floor crossbeam 6 are joined such that the upper surfaces 3c of the side beam and 711 of the crossbeam are aligned in the vertical direction of the vehicle. The side beam ridge 3e, which forms the upper surface 3c of the side beam in the side beam 3 and extends in the longitudinal direction of the vehicle, and the crossbeam ridge 61 (upper beam ridge 70a), which forms the upper surface 711 of the crossbeam in the floor crossbeam 6 and extends in the width direction, are both more rigid than other parts in their respective components. Thus, the ridges (3e, 61) with higher rigidity in their respective components are approximately orthogonal in their extension directions in the top view, but are located at approximately the same position in the vertical direction of the vehicle. That is, the crossbeam ridge 61 (upper beam ridge 70a) of the floor crossbeam 6 and the side beam ridge 3e of the side beam 3 are continuous. Therefore, the lower body structure of the vehicle 1 can efficiently transfer lateral collision loads from one side beam 3 to the other side beam 3.

[0110] Furthermore, the front floor panel 4, the upper beam 70, and the lower beam 80, positioned between the upper beam 70 and the lower beam 80, form a closed section in the longitudinal section along the longitudinal direction. Therefore, compared to the cross-sectional area of ​​the floor beam consisting solely of the upper beam fixed to the upper surface 4a of the floor panel, the cross-section of the floor beam 6, which functions as a load-transferring member in the vehicle width direction that transmits lateral collision loads from one side beam 3 to the other side beam 3, is enlarged in the longitudinal section along the longitudinal direction of the vehicle.

[0111] Therefore, the floor beam 6, which functions as a transfer member for transmitting lateral collision loads from one side beam 3 to another, has increased cross-sectional strength in the longitudinal section in the longitudinal direction, enabling efficient transmission of lateral collision loads from one side beam 3 to another. Thus, in the lower body structure of the vehicle 1, where the front floor panel 4 is located above the side beams 3 at the center position in the vertical direction, the desired lateral collision performance can be ensured.

[0112] In addition, in the upper beam 70, the ridge portion extending along the vehicle width direction is designated as the upper beam ridge portion 70a, and the upper beam 70 has three or more upper beam ridge portions 70a arranged at intervals in the vehicle front-rear direction.

[0113] With this structure, there are more than three upper edge sections in the upper beam 70 that have higher rigidity than other parts, thus further increasing the cross-sectional strength of the upper beam 70.

[0114] Therefore, the cross-sectional strength of the floor beam 6, which consists of an upper beam 70 with further increased cross-sectional strength and a lower beam 80 separated from the front floor panel 4, can be further increased. Thus, the lower body structure of vehicle 1 can improve its function as a load-transferring component in the vehicle width direction.

[0115] In addition, in the lower beam 80, the ridge portion extending in the vehicle width direction is called the lower beam ridge portion 80a, and the lower beam 80 has three or more lower beam ridge portions 80a arranged at intervals in the vehicle front-rear direction.

[0116] With this structure, there are more than three lower ridge sections in the lower beam 80 with higher rigidity than other parts, thus further increasing the cross-sectional strength of the lower beam 80.

[0117] Therefore, the cross-sectional strength of the floor beam 6, which forms a closed cross-section via the front floor panel 4 and is further increased by the upper beam 70 and lower beam 80, whose cross-sectional strength has been further increased. Therefore, the lower body structure of the vehicle 1 can further improve its function as a load-transferring member in the vehicle width direction.

[0118] In addition, the floor crossbeam 6 has a main body 60 between the seat brackets 622, 64 located at both ends in the vehicle width direction and connected to the side beams 3, and between the seat brackets 622, 64 on both sides in the vehicle width direction. The upper beam 70 in the main body 60 has an upwardly projecting portion 71 that is spaced apart in the vehicle longitudinal direction and has an upper surface 711 of the crossbeam, and an upper concave portion 72 that connects the upper convex portions 71 in the vehicle longitudinal direction and is located below the vehicle than the upper surface 711 of the crossbeam. In the longitudinal section in the longitudinal direction, the upper beam 70 in the main body 60 is formed into a roughly M-shaped cross section by the spaced upper convex portions 71 and the upper concave portions 72. The lower beam 80 in the main body 60 has downwardly projecting convex portions 81 spaced apart in the longitudinal direction of the vehicle, and concave portions 82 connecting the convex portions 81 in the longitudinal direction of the vehicle, positioned above the lower end of the convex portions 81. In the longitudinal section in the longitudinal direction, the lower beam 80 in the main body 60 is formed into an approximately inverted M-shaped cross-section by the spaced-apart convex portions 81 and concave portions 82. Furthermore, the upper beam 70 and the lower beam 80 are joined by the upper concave portion 72 and the concave portion 82.

[0119] This structure further increases the cross-sectional strength of the floor beam 6. Specifically, it has a main body portion 60 between the front outer seat brackets 622 located at both ends in the vehicle width direction and connected to the side beams 3, and between each front outer seat bracket 622 on both sides in the vehicle width direction. The main body portion 60 of the upper beam 70 has an upwardly projecting portion 71 that protrudes upwards from the vehicle and is spaced apart in the vehicle longitudinal direction, having an upper surface 711 of the beam, and an upwardly concave portion 72 that connects each upwardly projecting portion 71 in the vehicle longitudinal direction and is located below the upper surface 711 of the beam. In the longitudinal section in the longitudinal direction, the main body portion 60 of the upper beam 70 is formed into a generally M-shaped cross section by the spaced-apart upwardly projecting portions 71 and upwardly concave portions 72. Therefore, at least six upper beam ridge portions 70a extending in the vehicle width direction are formed in the upper beam 70 at intervals in the vehicle longitudinal direction. Thus, an upper beam 70 with low height and high cross-sectional strength in the vertical direction of the vehicle can be constructed.

[0120] Furthermore, the main body portion 60 of the lower beam 80 has downwardly projecting portions 81 spaced apart in the longitudinal direction of the vehicle, and concave portions 82 connecting each downwardly projecting portion 81 in the longitudinal direction of the vehicle, positioned above the lower end of the downwardly projecting portions 81 and having a concave shape. In the longitudinal section in the longitudinal direction, the main body portion 60 of the lower beam 80 is formed into an approximately inverted M-shaped cross-section by the spaced-apart downwardly projecting portions 81 and concave portions 82. Therefore, at least six lower beam ridge portions 80a extending in the vehicle width direction are formed in the lower beam 80 at intervals in the longitudinal direction of the vehicle. As a result, a lower beam 80 with low height and high cross-sectional strength in the vertical direction of the vehicle can be constructed.

[0121] Furthermore, the upper beam 70 and the lower beam 80 are joined by the upper concave portion 72 and the lower concave portion 82. Thus, in the floor beam 6, which forms a closed cross section via the front floor panel 4, closed cross sections can be formed by the upper convex portion 71 and the lower convex portion 81 spaced apart in the vehicle's longitudinal direction. Therefore, two closed cross sections can be formed in the floor beam 6 composed of the upper beam 70 and the lower beam 80, further improving the cross-sectional strength of the floor beam 6. Therefore, the lower body structure of the vehicle 1 can further enhance its function as a load-bearing member in the vehicle width direction.

[0122] In addition, a floor protrusion 4c is provided on the front floor panel 4. The floor protrusion 4c extends along the vehicle width direction and protrudes in any direction in the vertical direction of the vehicle. The upper concave part 72, the floor protrusion 4c and the lower concave part 82 are stacked in the vertical direction of the vehicle. The upper beam 70 and the lower beam 80 are joined through the floor protrusion 4c by the upper concave part 72 and the lower concave part 82.

[0123] Through this structure, the upper concave portion 72, the floor convex portion 4c provided on the front floor panel 4 and extending along the vehicle width direction and protruding in either direction of the vehicle's vertical direction, and the lower concave portion 82 are stacked in the vehicle's vertical direction. The upper beam 70 and the lower beam 80 are joined through the floor convex portion 4c via the upper concave portion 72 and the lower concave portion 82.

[0124] Therefore, compared to the case where a flat front floor panel 4 is sandwiched between concave portions 72 and 82 to form a floor beam 6 with a closed cross section, this structure can keep the protrusion height of the lower convex portion 81, which is on the opposite side of the protrusion direction of the floor convex portion 4c, i.e., under the vehicle, low relative to the front floor panel 4, and ensure the cross section height of the floor beam 6 that forms the closed cross section.

[0125] Therefore, the cross-sectional strength of the floor beam 6, which consists of the upper beam 70 and the lower beam 80, can be further improved. Thus, the lower body structure of vehicle 1 can further enhance its function as a load-transferring component in the vehicle width direction.

[0126] In addition, the upper beam 70 and the lower beam 80 are provided with flange portions 65 that protrude along the vehicle width direction and in the front-rear direction of the vehicle. The upper beam 70 and the lower beam 80 are joined to the front floor panel 4 through the flange portions 65.

[0127] This structure allows the upper beam 70 and lower beam 80 to be firmly fixed to the front floor panel 4 via the flange 65. Therefore, the floor beam 6, which sandwiches the front floor panel 4 between the upper beam 70 and lower beam 80, can reliably form a closed section.

[0128] In addition, in the flange portion 65 formed along the vehicle width direction, a plurality of reinforcing ribs 66 extending in the vehicle front-rear direction are formed at intervals in the vehicle width direction, thereby improving the shape retention of the flange portion 65 that is long in the vehicle width direction.

[0129] Therefore, the shape retention of the upper beam 70 and lower beam 80 with flange 65 can be improved.

[0130] Furthermore, in the concave portions 72 and 82 formed along the vehicle width direction, a plurality of reinforcing ribs 66 extending along the vehicle front-rear direction are formed at intervals in the vehicle width direction, thereby improving the shape retention of the concave portions 72 and 82 that are long in the vehicle width direction.

[0131] Therefore, the shape retention of the upper beam 70 and lower beam 80, which have concave portions 72 and 82 with reinforcing ribs 66, can be improved.

[0132] In addition, the floor crossbeam 6 has a first floor crossbeam 6A located approximately at the center of the front floor panel 4 in the vehicle longitudinal direction and a second floor crossbeam 6B located at a predetermined interval behind the first floor crossbeam 6A at the rear of the vehicle.

[0133] This structure allows for the installation of two floor beams 6 at predetermined intervals in the longitudinal direction of the vehicle, forming a closed cross section that sandwiches the front floor panel 4. Therefore, the performance of the floor beams 6 in transmitting collision loads during lateral collisions in the vehicle width direction can be improved.

[0134] Therefore, in the lower body structure of the vehicle 1, where the front floor panel 4 is joined to the side beam 3 at the upper side of the center position in the vertical direction of the vehicle, the desired side collision performance can be ensured.

[0135] In the correspondence between the structure of the present invention and the above-described embodiments, The floor panel of this invention corresponds to the front floor panel 4, and so on. The joint portion corresponds to the front outer seat bracket 622. However, the present invention is not limited to the structure of the above embodiments, and various embodiments can be obtained.

[0136] For example, in the above embodiment, the first floor crossbeam 6A is joined to the side beam 3 via the front outer seat brackets 622 provided on both sides in the vehicle width direction, and the second floor crossbeam 6B is joined to the side beam 3 via the rear outer seat brackets 64 provided on both sides in the vehicle width direction. However, it can also be joined to the side beam 3 via connecting plates provided on both sides of the main body 60 in the vehicle width direction, or the two ends of the main body 60 can be directly joined to the side beam 3. Alternatively, the upper surface 711 of the crossbeam of the upper beam 70 constituting the main body 60 can be extended outward in the vehicle width direction and joined to the upper surface 3c of the side beam of the side beam 3.

[0137] Furthermore, in the aforementioned side beam 3, it is formed as a rectangular cross-section that is slightly longer than the vehicle width direction in the vehicle's longitudinal direction, but it can also be an inclined surface with the upper surface 3c of the side beam 3 inclined toward the center of the side beam 3 in the vehicle width direction. In this case, the upper surface 711 of the upper beam 70 constituting the floor crossbeam 6 can be positioned between the upper end position and the lower end position of the outer side beam 3a that is inclined in the vehicle's vertical direction.

[0138] Furthermore, the floor convex portion 4c of the front floor panel 4, formed by the concave portion 72 of the upper beam 70 and the concave portion 82 of the lower beam 80, protrudes upwards from the vehicle, but it is also possible for the floor convex portion 4c to protrude downwards from the vehicle. In this case, the lower beam 80 is positioned above the vehicle on the front floor panel 4 and fixed to the upper surface 4a of the floor panel, while the upper beam 70 is positioned below the vehicle on the front floor panel 4 and fixed to the lower surface 4b of the floor panel, which can suppress the upward protrusion height of the floor crossbeam 6.

[0139] [Numbering Explanation] 1…vehicles 3…Side beams 3c… Upper surface of side beam 4…Front floor panel 4a…Top surface of floor panel 4b…Underside surface of floor panel 4c…Floor convexity 6…Floor beams 6A…First floor beam 6B…Second Floor Beam 60…Main body 70…Raising the roof beam 70a… Upper beam edge section 71…Upper convex part 72… concave portion 80…lower beam 80a… Lower beam edge section 81…lower convex part 82… concave portion 622…Front outer seat bracket 711… Upper surface of the crossbeam

Claims

1. A lower body structure for a vehicle, characterized in that: It possesses: The left and right side beams are paired and extend along the front and rear directions of the vehicle at both ends of the floor panel in the vehicle width direction. A floor beam extends along the vehicle width direction and connects the paired left and right side beams; wherein, The side beam has an upper surface facing upwards towards the vehicle and forms a closed section in the longitudinal section along the vehicle width direction. The floor beams have the following features: The upper beam is fixed to the upper surface of the floor panel, which is the upper surface of the floor panel, protrudes upward toward the vehicle, and has a crossbeam upper surface facing upward toward the vehicle; The lower beam is fixed to the lower surface of the floor panel, which is the lower surface of the floor panel, and protrudes downwards from the vehicle. The side beam and the floor crossbeam are joined in such a way that the upper surfaces of the side beam and the upper surfaces of the crossbeam are aligned in the vertical direction of the vehicle; The floor panel, the upper beam, and the lower beam, configured between the upper beam and the lower beam, form a closed section in the longitudinal section along the front-rear direction of the vehicle.

2. The lower body structure of the vehicle according to claim 1, characterized in that: In the upper beam, the ridge portion extending along the vehicle width direction is designated as the upper beam ridge portion, and the upper beam has three or more upper beam ridge portions arranged at intervals in the vehicle's longitudinal direction.

3. The lower body structure of the vehicle according to claim 2, characterized in that: In the lower beam, the ridge line extending along the vehicle width direction is designated as the lower beam ridge line. The lower beam has three or more lower beam ridges arranged at intervals in the longitudinal direction of the vehicle.

4. The lower body structure of the vehicle according to claim 3, characterized in that: The floor beam has a joint portion located at both ends in the vehicle width direction and engaging with the side beam, and a main body portion between each of the joint portions on both sides in the vehicle width direction; The upper beam constituting the main body has: The upper convex portion protrudes upwards from the vehicle and is spaced apart in the longitudinal direction of the vehicle, having the upper surface of the crossbeam; The upper concave portion, which connects each of the upper convex portions in the longitudinal direction of the vehicle, is positioned below the vehicle and is closer to the upper surface of the crossbeam than the vehicle. In a longitudinal section along the front-rear direction of the vehicle, the upper beam constituting the main body is formed into an approximately M-shaped cross section by the upper convex and upper concave portions arranged at intervals. The lower beam constituting the main body has: A convex portion that protrudes downwards from the vehicle and is spaced apart in the longitudinal direction of the vehicle; A concave portion, which connects each of the convex portions in the longitudinal direction of the vehicle, is positioned above the vehicle and is concave compared to the lower end of the convex portions; In a longitudinal section along the front-rear direction of the vehicle, the lower beam constituting the main body is formed into an approximately inverted M-shaped cross section by the convex and concave portions arranged at intervals. The upper beam and the lower beam are joined by the upper concave portion and the lower concave portion.

5. The lower body structure of the vehicle according to claim 4, characterized in that: The floor panel is provided with a floor protrusion that extends along the vehicle width direction and protrudes in any direction in the vertical direction of the vehicle. The upper concave portion, the floor convex portion, and the lower concave portion are stacked in the vertical direction of the vehicle; The upper beam and the lower beam are joined via the convex portion of the floor through the upper concave portion and the lower concave portion.

6. The lower body structure of the vehicle according to claim 1, characterized in that: The upper beam and the lower beam are provided with flange portions that protrude along the vehicle width direction and in the front-rear direction of the vehicle. The upper beam and the lower beam are joined to the floor panel via the flange portion.

7. The lower body structure of the vehicle according to claim 6, characterized in that: In the flange portion formed along the vehicle width direction, a plurality of reinforcing ribs extending along the front-rear direction of the vehicle are formed at intervals in the vehicle width direction.

8. The lower body structure of the vehicle according to claim 1, characterized in that: The floor beams have the following features: The first floor crossbeam is positioned approximately at the center of the floor panel in the vehicle's longitudinal direction. The second floor crossbeam is positioned at a predetermined interval behind the first floor crossbeam of the vehicle.

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