Floor panel connection structure for a vehicle underbody and vehicle underbody

Abstract

The present disclosure relates to a floor panel connection structure of a vehicle underbody and a vehicle underbody, wherein the floor panel connection structure of the vehicle underbody is configured to connect a floor panel to side sills located on both sides of the underbody, the floor panel connection structure comprising a plurality of box panels, each box panel comprising an open portion and a closed portion, wherein the box panels are configured to be connected to each other in a vehicle width direction, and wherein a first box panel is coupled to a first side sill through the open portion of the first box panel, and a second box panel is coupled to a second side sill through the open portion of the second box panel.

Description

[0001] Cross-citation of related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2020-0176334, filed on December 16, 2020, which is incorporated herein by reference. Technical Field

[0003] This invention relates to a bottom plate connection structure for the lower body of a vehicle. Background Technology

[0004] Recently, the automotive industry has introduced new concepts and visions for the future of mobility, aiming to realize a dynamic, human-centered future city. One of these future modes of mobility is the purpose-based personal vehicle (PBV).

[0005] PBV is an environmentally friendly mobility solution that provides passengers with the customized services they need during the journey from origin to destination, and can use electric vehicle-based artificial intelligence to perform optimal route booking and convoy driving for each situation.

[0006] The PBV consists of a lower body (also known in the industry as a rolling chassis or skateboard lower body) and an upper body mounted on the lower body.

[0007] An intermediate floor panel connects the front bulkhead panel on the front side and the rear floor panel panel on the lower body. The intermediate floor panel is a single unit that combines multiple panel components, and it is connected to the inner sides of the two side beams of the lower body.

[0008] However, the use of multiple mold assemblies to manufacture panel components with various cross-sections and the assembly of these panel components with the corresponding total length and width of the lower body typically leads to increased equipment investment and production costs.

[0009] Typically, during a side collision, when the collision load is concentrated on the side beam of the lower body, the side collision performance may be degraded due to the rotational deformation of the side beam.

[0010] The information disclosed in this background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0011] This invention relates to a floor plate connection structure for the lower body of a vehicle. A specific embodiment relates to a floor plate connection structure for the lower body of a PBV (Personal Purpose Vehicle).

[0012] Embodiments of the present invention provide a floor connecting structure of a vehicle underbody that can be configured with panel members having the same cross section.

[0013] A floor connecting structure of a vehicle underbody according to exemplary embodiments of the present invention connects a floor panel to side sills located on both sides of the underbody, and the floor connecting structure can include at least two box-type panels including an open portion and a closed portion insertable into the open portion, the box-type panels being connected to each other in a vehicle width direction by the open portion and the closed portion, and coupled to the side sills through the open portion.

[0014] The floor connecting structure according to exemplary embodiments of the present invention can include a main assembly that is a pair of box-type panels connected by closed portions facing each other.

[0015] The floor connecting structure according to exemplary embodiments of the present invention can further include a sub-assembly in which remaining box-type panels connected to each other by open portions and closed portions are connected to open portions of the main assembly.

[0016] In the sub-assembly, the open portion of the outermost box-type panel corresponding to the side sill is formed with a connecting flange connected to an inner side portion of the side sill.

[0017] In the main assembly, the closed portions of the box-type panels facing each other can be joined in the vehicle width direction.

[0018] The box-type panels can include a "U"-shaped cross section, the box-type panels can be connected to each other and joined to the side sills and can have a rectangular-shaped closed cross section.

[0019] The open portion of the box-type panel can have a height greater than a height of the closed portion.

[0020] The closed portion of the box-type panel can include a joggle step that is stepped from the open portion, and the closed portion can have a lower height than the open portion by the joggle step.

[0021] On upper surfaces of the closed portions facing each other in the main assembly, rib seating portions in which ribs of a carpet are fitted can be formed by joggle steps.

[0022] The open portion of the box-type panel can include a connecting flange connected to an inner surface of an inner side portion of the side sill in the vehicle width direction.

[0023] The open portion of the box-type panel can include a connecting flange engaged with an upper surface and a lower surface of the inner side portion of the side sill in a vertical direction.

[0024] The open portion of the box panel can include an inclined surface whose cross-sectional height decreases in the direction of the closed portion from the connecting flange.

[0025] According to embodiments of the present application, since a floor capable of corresponding to the overall length and width of various vehicle models can be configured by the cross-section of the box panel, investment costs for mold equipment and production costs can be reduced.

[0026] In addition, effects obtained or predicted by exemplary embodiments of the present application will be directly or implicitly disclosed in the detailed description of exemplary embodiments of the present application. That is, various effects predicted by exemplary embodiments of the present application will be disclosed in the detailed description that will be described later. BRIEF DESCRIPTION OF DRAWINGS

[0027] These drawings are for merely referring to in describing exemplary embodiments of the present application, and thus, the technical idea of the present application should not be construed as being limited to these drawings.

[0028] Figure 1 FIG. 1 is a view showing a vehicle lower body according to an exemplary embodiment of the present application.

[0029] Figure 2 FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. Figure 1

[0030] Figure 3 FIG. 4 is a view showing a box panel applied to a floor connection structure of a vehicle lower body according to an exemplary embodiment of the present application.

[0031] Figure 4 FIG. 5 is a view showing a main assembly applied to a floor connection structure of a vehicle lower body according to an exemplary embodiment of the present application.

[0032] Figure 5 FIG. 6 is a view showing a sub-assembly applied to a floor connection structure of a vehicle lower body according to an exemplary embodiment of the present application.

[0033] Figure 6 FIG. 7 is a view showing a combination of a box panel and a side beam applied to a floor connection structure of a vehicle lower body according to an exemplary embodiment of the present application.

[0034] Figure 7 FIG. 8 is a cross-sectional view showing a floor connection structure of a vehicle lower body according to another exemplary embodiment of the present application.

[0035] Figure 8 FIG. 9 is a cross-sectional view showing a floor connection structure of a vehicle lower body according to another exemplary embodiment of the present application.

[0036] ​Embodiments of the present application can be described below using the following elements in conjunction with the accompanying drawings.

[0037] 1: lower body

[0038] 3: chassis frame

[0039] 5: side beam

[0040] 6: side beam inner portion

[0041] 7: intermediate floor panel

[0042] 8: front bulkhead

[0043] 9: rear floor panel

[0044] 10: box panel

[0045] 11: open portion

[0046] 12a, 14a: upper surface

[0047] 12b, 14b: lower surface

[0048] 13: closed portion

[0049] 14c: side surface

[0050] 15: opening

[0051] 17: joining step

[0052] 19: closed cross-section

[0053] 30: main assembly

[0054] 33: rib seating portion

[0055] 50: sub-assembly

[0056] 60: spot weld gun

[0057] 71: carpet

[0058] 73: rib

[0059] 81, 91: connecting flange

[0060] 93: inclined surface

[0061] hi, h2: height 100, 200, 300: floor connection structure DETAILED DESCRIPTION

[0062] The present application will be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments of the application are shown. As this description proceeds, this application will become apparent from the following detailed description, the DETAILED DESCRIPTION, and the drawings. Changes in the order of the blocks or steps for carrying out the methods can be understood by those skilled in the art.

[0063] In order to clearly describe embodiments of the present application, portions unrelated to the description are omitted, and throughout the specification, the same or similar components are attached with the same reference numerals.

[0064] Since the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, the present application is not necessarily limited to the size and thickness shown in the drawings, and the thickness is exaggerated to clearly express the respective portions and regions.

[0065] In addition, in the following detailed description, the names of configurations are divided into first, second, and the like to distinguish the configurations in the same relationship, and the configurations are not necessarily limited to the order described below.

[0066] Throughout the specification, when a portion includes a certain component, it means that other components can also be included rather than excluding other components, unless otherwise specifically stated.

[0067] In addition, the terms such as "…unit", "…device" described in the specification are units of a comprehensive structure that performs at least one function or operation.

[0068] Figure 1 is a view showing a vehicle lower body of an exemplary embodiment of the present application.

[0069] Referring to Figure 1 The floor connection structure 100 of the vehicle lower body according to the exemplary embodiment of the present application can be applied, for example, to a special purpose vehicle (PBV) based on an electric vehicle.

[0070] Here, the PBV is an environmentally friendly travel vehicle that provides a passenger with a desired customized service during a travel time from a departure place to a destination. The PBV is capable of setting an optimal route for each situation and clustering travel and can also be a box-type design vehicle having a large interior space.

[0071] Such a PBV includes a skateboard-type lower body 1 and includes an upper body (not shown in the drawings) mounted on the lower body 1 as a monocoque body.

[0072] The lower body 1 is also called a rolling chassis in the industry and includes a chassis frame 3 on which a battery assembly (not shown in the drawings) can be installed. Also, the upper body is a body coupled to the lower body 1 and can constitute a vehicle cabin. The upper body can be a space frame formed of a framework connected by, for example, a steel plate or a pipe material.

[0073] In the industry, the vehicle width direction is referred to as the L direction, the length direction of the vehicle body (the front-rear direction or the overall length direction) is the T direction, and the height direction of the vehicle body is the H direction. However, in the embodiment of the present application, instead of setting the LTH directions as described above as reference directions, components are described hereinafter by setting the vehicle width direction, the vehicle body front-rear direction, and the vertical direction.

[0074] Furthermore, the end (one end or the other end / one end or one end) hereinafter can be defined as either end or a specific portion including the end (one end or the other end / one end or one end).

[0075] The exemplary embodiment of the present application is applied to the lower body 1, and the intermediate floor panel 7 is coupled to the side beams 5 located on both sides in the vehicle width direction in the chassis frame 3. Here, a dash panel 8 is connected to the front portion of the intermediate floor panel 7, and a rear floor panel 9 is connected to the rear portion of the intermediate floor panel 7.

[0076] Hereinafter, as a floor connection structure 100 of a vehicle lower body according to the exemplary embodiment of the present application, the connection structure of the intermediate floor panel 7 coupled to the side beams 5 located on both sides of the lower body 1 will be described.

[0077] In the exemplary embodiment of the present application, the floor connection structure 100 of the vehicle lower body constitutes the intermediate floor panel 7 and the floor, in which the intermediate floor panel contains panel members having the same cross section, and the floor can correspond to the overall length and width of various vehicle models.

[0078] Figure 2 is a cross-sectional view taken along the line A-A of Figure 1 .

[0079] Referring to Figure 2 , the floor connection structure 100 of the vehicle lower body according to the exemplary embodiment of the present application includes at least two box panels 10 as a main assembly 30 and a sub assembly 50.

[0080] In the exemplary embodiment of the present application, the box panels 10 constitute the intermediate floor panel 7 as shown in Figure 1 and are provided with a plurality of box panels. The box panels 10 are provided in the shape of a box open in one direction, in which one side is open. For example, the box panels 10 can have a "U" shaped cross section containing a top surface, a bottom surface, and a side surface.

[0081] As shown in Figure 1 , the box panels 10 are provided between the dash panel 8 and the rear floor panel 9 of the lower body 1 in the front-rear direction of the vehicle body, are connected to each other in the vehicle width direction, and are coupled to the side beams 5.

[0082] Figure 3 FIG. 10 is a view showing a box panel applied to a floor connecting structure of a lower body of a vehicle according to an exemplary embodiment of the present application.

[0083] Reference Figure 2 and Figure 3 The box panel 10 includes an open portion 11 formed on one side in the vehicle width direction and a closed portion 13 formed on the other side in the vehicle width direction.

[0084] The open portion 11 includes an upper surface 12a and a lower surface 12b, and an opening 15 is formed between the upper surface 12a and the lower surface 12b in the vehicle width direction.

[0085] The closed portion 13 includes an upper surface 14a and a lower surface 14b integrally connected to the open portion 11, and a side surface 14c connecting the upper surface 14a and the lower surface 14b.

[0086] The closed portion 13 of one box panel 10 can be inserted into the open portion 11 of any other box panel 10 through the upper surface 14a, the lower surface 14b, and the side surface 14c. The height h2 of the open portion 11 of the box panel 10 is greater than the height hi of the closed portion 13.

[0087] The closed portion 13 includes a joining step portion 17 that is stepped from the open portion 11. The joining step portion 17 can be formed by a molding method by forming a portion of a plate into a step portion. Accordingly, the closed portion 13 can be formed to have a lower height than the open portion 11 due to the joining step portion 17.

[0088] The box panel 10 as described above is connected to each other in the vehicle width direction by the open portion 11 and the closed portion 13, and can be coupled to the side beam inner side portion 6 of the side beam 5 through the open portion 11.

[0089] The box panel 10 has a "U" shaped cross section, and when the box panel 10 is connected to each other in the vehicle width direction by the open portion 11 and the closed portion 13, a closed cross section 19 having an approximately rectangular shape can be formed between the side beam inner side portions 6.

[0090] The connecting structure of these box panels 10 and the connecting structure of the box panel 10 and the side beam inner side portion 6 will be described in more detail later.

[0091] In the exemplary embodiment of the present application, the main assembly 30 is provided as an assembly in which a pair of box panels 10 are connected to each other by the closed portions 13 facing each other. The main assembly 30 can be provided as a reference assembly located at a middle portion in the entire middle floor area, as shown in the drawings.

[0092] Figure 4 is a view showing a main assembly applied to the floor panel connection structure of the vehicle underbody according to the exemplary embodiment of the present application.

[0093] As an alternative, a main assembly 30 including a pair of box panels 10 facing each other and connected to each other by the closed portion 13 can constitute the entire intermediate floor panel 7 (refer to Figure 1 ), and the open portion 11 can also be connected to the side sill inner side portion 6. However, in the following, an example in which the main assembly 30 is located at the intermediate portion of the intermediate floor panel 7 will be described.

[0094] In this main assembly 30, as shown in Figure 4 , a pair of box panels 10 are provided to face each other in the vehicle width direction by the closed portion 13. That is, the closed portions 13 of the box panels 10 are provided to face each other in the vehicle width direction by the side surfaces 14c. In this way, the side surfaces 14c of the closed portions 13 facing each other are joined in the vehicle width direction.

[0095] Here, the side surfaces 14c of the closed portions 13 facing each other are joined by spot welding by the spot welding gun 60. In this case, the spot welding gun 60 enters the inside of the closed portion 13 through the open portion 11 opened in the opposite direction in the vehicle width direction, and spot welds the side surfaces 14c of the closed portions 13 facing each other in the vehicle width direction.

[0096] Further, when the closed portions 13 of the box panels 10 facing each other are joined to each other as described above, the ribs 73 protruding from the bottom surface of the carpet 71 are fitted to the upper surfaces 14a of the closed portions 13. The rib 73 protruding from the bottom surface of the carpet 71 can be fitted in a rib seating portion 33 formed in the upper surface 14a of the closed portion 13 by incorporating the step portion 17.

[0097] Figure 5 is a view showing a sub assembly applied to the floor panel connection structure of the vehicle underbody according to the exemplary embodiment of the present application.

[0098] Referring to Figure 2 to Figure 5 , in the exemplary embodiment of the present application, a sub assembly 50 can be formed of a plurality of box panels 10 connected to each other by the open portion 11 and the closed portion 13. It can also be constituted by the box panels 10 connected to the open portion 11 of the main assembly 30. That is, the sub assembly 50 can be connected to both sides of the main assembly 30 in the vehicle width direction, with the main assembly 30 interposed between the sub assemblies.

[0099] The box panel 10 of the sub assembly 50 is inserted into the open portion 11 on both sides of the main assembly 30 by the closed portion 13. In addition, the box panel 10 of the sub assembly 50 is inserted into the open portion 11 by the closed portion 13, and the box panel of the sub assembly can be provided in the vehicle width direction.

[0100] In a state in which the closed portion 13 is inserted into the open portion 11 as described above, the upper surface 12a and the lower surface 12b of the open portion 11 and the upper surface 14a and the lower surface 14b of the closed portion 13 are spot-welded by the spot-welding gun 60.

[0101] In this case, the spot-welding gun 60 enters the inside of the closed portion 13 through the open portion 11, and can spot-weld the upper surface 12a of the open portion 11 and the upper surface 14a of the closed portion 13 and the lower surface 12b of the open portion 11 and the lower surface 14b of the closed portion 13 in the up-and-down direction.

[0102] Figure 6 is a view showing a combination of a box panel and a side beam applied to a floor connection structure of a vehicle lower body according to an exemplary embodiment of the present application.

[0103] In the sub assembly 50 as described above, the open portion 11a of the outermost box panel 10a is coupled to the side beam inner side portion 6 of the side beam 5. The open portion 11a includes a connecting flange 81 that is joined to the inner surface of the side beam inner side portion 6.

[0104] The connecting flange 81 is joined to the inner surface of the side beam inner side portion 6 in the vehicle width direction by spot-welding by the spot-welding gun 60. As described above, the spot-welding gun 60 enters the inner side of the side beam inner side portion 6, and can spot-weld the inner surface of the side beam inner side portion 6 and the connecting flange 81 in the vehicle width direction.

[0105] Hereinafter, the assembly process of the floor connection structure 100 of the vehicle lower body according to the exemplary embodiment of the present application configured as described above will be described in detail with reference to the above disclosed drawings.

[0106] In the exemplary embodiment of the present application, a pair of box panels 10 are provided to face each other in the vehicle width direction by the closed portion 13. Then, in the exemplary embodiment of the present application, the side surfaces 14c of the closed portions 13 facing each other in the vehicle width direction are spot-welded, and the main assembly 30 is assembled.

[0107] Subsequently, in the exemplary embodiment of the present application, the closed portions 13 of other box panels 10 are inserted into the open portions 11 located on both sides of the main assembly 30. Thereafter, in the exemplary embodiment of the present application, the closed portions 13 of other box panels 10 are inserted into the open portions 11 of the aforementioned other box panels 10, and in this way, the main assembly 30 is interposed between a plurality of box panels 10.

[0108] Next, in the exemplary embodiment of the present application, the upper surfaces 12a of the open portions 11 and the upper surfaces 14a of the closed portions 13, and the lower surfaces 12b of the open portions 11 and the lower surfaces 14b of the closed portions 13, which overlap each other in the up-down direction, are spot-welded. That is, the sub assembly 50 is assembled on both sides of the main assembly 30 in the vehicle width direction.

[0109] The operations can be additionally performed depending on the length of the box panel 10 and the vehicle width and the vehicle length.

[0110] Then, in the exemplary embodiment of the present application, the open portion 11 of the box panel 10a located on the outermost side of the sub assembly 50 is joined to the inner side portion 6 of the side beam 5. In this process, the inner surface of the inner side portion 6 and the connecting flange 81 are spot-welded in the vehicle width direction.

[0111] Thus, in the exemplary embodiment of the present application, the box panels 10 having the same cross section are connected to each other by a series of assembly processes as described above, and the intermediate floor panel 7 of the lower body 1 is formed.

[0112] According to the floor connecting structure 100 of the vehicle lower body according to the embodiment of the present application described thus far, a floor that can correspond to the overall length and width of a plurality of vehicle models can be configured by box panels 10 having the same cross section. And thus, the investment cost and the production cost of mold equipment and the like can be reduced.

[0113] Further, in the embodiment of the present application, since the closed cross section 19 having a rectangular shape is formed in the vehicle width direction in the box panels 10 connected to each other, the strength and the rigidity of the floor can be improved.

[0114] Figure 7 is a cross-sectional view showing a floor connecting structure of a vehicle lower body according to another exemplary embodiment of the present application.

[0115] For ease of understanding, in the drawings, the same reference numerals are assigned to the same components as those of the aforementioned embodiment.

[0116] Reference Figure 7The floor connecting structure 200 of the vehicle underbody according to another exemplary embodiment of the present application is based on the structure of the aforementioned exemplary embodiment. In addition, the outermost box panel 10b can include an open portion 11b in which a connecting flange 91 is formed to be joined to upper and lower surfaces of the side beam inner side portion 6b in the vertical direction.

[0117] The box panel 10b is a panel that is coupled to the side beam inner side portion 6b, and the connecting flange 91 is integrally formed in the open portion 11b of the box panel 10b. The connecting flange 91 overlaps the upper and lower surfaces of the side beam inner side portion 6b, and can be joined in the up-and-down direction by spot welding.

[0118] Accordingly, in another exemplary embodiment of the present application, when the side surface of the vehicle collides, it absorbs the collision load concentrated on the side beam 5 and disperses the collision load, minimizing the rotational deformation of the side beam 5, thereby reducing damage to the battery assembly and injury to the occupant.

[0119] The remaining configuration and effects of the floor connecting structure 200 of the vehicle underbody according to the embodiment of the present application as described above are the same as those of the aforementioned exemplary embodiment, so a detailed description will be omitted.

[0120] Figure 8 is a cross-sectional view illustrating a floor connecting structure of a vehicle underbody according to another exemplary embodiment of the present application.

[0121] For ease of understanding, in the drawings, the same reference numerals are assigned to the same components as those of the aforementioned embodiment.

[0122] Reference Figure 8 The floor connecting structure 300 of the vehicle underbody according to another exemplary embodiment of the present application is based on the structure of the aforementioned exemplary embodiment. In addition, the box panel 10c can include an open portion 11c of the box panel 10c having a sloped surface 93 that is inclined from the connecting flange 91 toward the closed portion 13c, which is joined to upper and lower surfaces of the side beam inner side portion 6c in the up-and-down direction.

[0123] The box panel 10c is a panel that is coupled to the side beam inner side portion 6c, and the connecting flange 91c and the sloped surface 93 can be integrally formed on the open portion 11c of the box panel 10c. In the above, the sloped surface 93 can be formed with a cross-sectional shape whose height gradually decreases from the connecting flange 91c to the closed portion 13c.

[0124] Therefore, in another exemplary embodiment of the present application, when a side surface of the vehicle collides, the collision load concentrated on the side beam 5 is absorbed by the inclined surface 93 and dispersed, so that the side surface collision performance of the vehicle can be further improved.

[0125] Since the remaining configuration and effects of the floor connection structure 300 of the vehicle lower body according to the other exemplary embodiment of the present application as described above are the same as those of the aforementioned exemplary embodiment, detailed description will be omitted.

[0126] While the present application has been described in connection with the exemplary embodiments, as contemplated to be presently preferred, it is to be understood that the application is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and equivalent arrangements.

Claims

1. A floor plate connection structure for a vehicle lower body, the floor plate connection structure being configured to connect a floor plate panel to side beams located on both sides of the lower body, the floor plate connection structure comprising: A plurality of box-type panels, each including an open portion and a closed portion, wherein the box-type panels are configured to be connected to each other along the width direction of the vehicle, and wherein the plurality of box-type panels includes a first box-type panel and a second box-type panel, the first box-type panel being connected to a first side beam via an open portion of the first box-type panel, and the second box-type panel being connected to a second side beam via an open portion of the second box-type panel. Each of the box-type panels has a "U"-shaped cross-section, and these box-type panels are connected to each other and joined to the side beams, having a closed cross-section in a rectangular shape. The base plate connection structure further includes a main component, which comprises a third box-type panel and a fourth box-type panel. The closed portions of the third box-type panel and the fourth box-type panel are arranged to face each other and be connected to each other. The closed portion of the third box panel includes a first connecting step portion that is stepped from the open portion of the third box panel, and the closed portion of the third box panel has a lower height than the open portion of the third box panel due to the first connecting step portion. The closed portion of the fourth box panel includes a second connecting step portion that is stepped from the open portion of the fourth box panel, and the closed portion of the fourth box panel has a lower height than the open portion of the fourth box panel due to the second connecting step portion. The rib mounting portion is formed by the first and second joint steps; and The carpet ribs are fitted into the rib mounting portion.

2. The base plate connection structure according to claim 1 further includes a sub-assembly, the sub-assembly including a fifth box panel disposed between the first box panel and the third box panel, wherein the closed portion of the fifth box panel is connected to the open portion of the third box panel of the main assembly, and the open portion of the fifth box panel is connected to the closed portion of the first box panel.

3. The base plate connection structure according to claim 2 further includes a connecting flange, the connecting flange being located in the open portion of the first box-type panel and connected to the inner side of the side beam corresponding to the first side beam.

4. The base plate connection structure according to claim 1, wherein, The closed portions of the third box panel and the fourth box panel are joined in the vehicle width direction.

5. The base plate connection structure according to claim 1, wherein, The height of the open portion of each of the box-type panels is greater than the height of the closed portion.

6. The base plate connection structure according to claim 1, wherein, Each of the box-type panels has a closed portion including a step portion that extends from the open portion, and the closed portion of the box-type panel has a lower height than the open portion due to the step portion.

7. The base plate connection structure according to claim 1, wherein, The open portion of the first box-type panel includes a connecting flange that connects to the inner surface of the inner side portion of the side beam in the vehicle width direction.

8. The base plate connection structure according to claim 1, wherein, The open portion of the first box-type panel includes a connecting flange that engages with the upper and lower surfaces of the inner side of the side beam in the vertical direction.

9. The base plate connection structure according to claim 8, wherein, The open portion of the first box panel includes an inclined surface, the height of which decreases from the connecting flange along the closed portion of the first box panel.

10. A floor plate connection structure for a vehicle underbody, the floor plate connection structure comprising: The first box panel and the second box panel each include an open section and a closed section; The closed portions of the first box panel and the closed portions of the second box panel face each other and are connected to each other along the width direction of the vehicle. The first box-type panel is connected to the first side beam through its open portion; and The second box-type panel is connected to the second side beam through its open portion. Each of the box-type panels has a "U"-shaped cross-section, and these box-type panels are connected to each other and joined to the side beams, having a closed cross-section in a rectangular shape. The upper surface of the closed portion of the first box panel includes a first connecting step portion that is stepped from the open portion of the first box panel, and the closed portion of the first box panel has a lower height than the open portion of the first box panel due to the first connecting step portion. The upper surface of the closed portion of the second box-type panel includes a second connecting step portion that extends from the open portion of the second box-type panel in a stepped manner, and the closed portion of the second box-type panel has a lower height than the open portion of the second box-type panel due to the second connecting step portion; and The first and second joint steps form a rib mounting portion. The carpet ribs are fitted into the rib mounting portion.

11. The base plate connection structure according to claim 10 further includes a first connecting flange, the first connecting flange being located in the open portion of the first box-type panel and connected to the inner side of the first side beam corresponding to the first side beam.

12. The base plate connection structure according to claim 11 further includes a second connecting flange, the second connecting flange being located in the open portion of the second box-type panel and connected to the inner side of the second side beam corresponding to the second side beam.

13. A vehicle lower body, comprising: Front bulkhead; Rear bottom panel; and A middle floor panel is disposed between the front bulkhead and the rear floor panel in the longitudinal direction of the vehicle's lower body. The middle floor panel comprises a plurality of box-type panels, each including an open portion and a closed portion. The box-type panels are connected to each other along the vehicle's width direction. The plurality of box-type panels includes a first box-type panel and a second box-type panel. The first box-type panel is connected to a first side beam via its open portion, and the second box-type panel is connected to a second side beam via its open portion. Each of the box-type panels has a "U"-shaped cross-section, and these box-type panels are connected to each other and joined to the side beams, having a closed cross-section in a rectangular shape. The vehicle's lower body further includes a third box-type panel and a fourth box-type panel. The closed portions of the third box-type panel and the fourth box-type panel are arranged facing each other and connected to each other. The third box-type panel and the fourth box-type panel are positioned between the first box-type panel and the second box-type panel in the vehicle width direction. The closed portion of the third box panel includes a first connecting step portion that is stepped from the open portion of the third box panel, and the closed portion of the third box panel has a lower height than the open portion of the third box panel due to the first connecting step portion. The closed portion of the fourth box panel includes a second connecting step portion that is stepped from the open portion of the fourth box panel, and the closed portion of the fourth box panel has a lower height than the open portion of the fourth box panel due to the second connecting step portion. The rib mounting portion is formed by the first and second joint steps; and The carpet ribs are fitted into the rib mounting portion.

14. The vehicle lower body according to claim 13, further comprising: A fifth box panel is disposed between the first box panel and the third box panel, wherein the closed portion of the fifth box panel is connected to the open portion of the third box panel, and the open portion of the fifth box panel is connected to the closed portion of the first box panel. as well as A sixth box-type panel is disposed between the fourth box-type panel and the second box-type panel, wherein the closed portion of the sixth box-type panel is connected to the open portion of the fourth box-type panel, and the open portion of the sixth box-type panel is connected to the closed portion of the second box-type panel.

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