Vehicle floor assembly

Abstract

The utility model discloses a vehicle floor assembly which comprises a floor body, a left wheel cover is arranged on the left side of the floor body, and a right wheel cover is arranged on the right side of the floor body. The left wheel cover stiffening beam and the right wheel cover stiffening beam are arranged on the floor body, the left wheel cover stiffening beam is close to a joint where the left wheel cover is connected with the floor body, and the right wheel cover stiffening beam is close to a joint where the right wheel cover is connected with the floor body; the NVH performance of the vehicle chassis can be improved, abnormal noise generated during driving is reduced, and the collision safety of the vehicle chassis is optimized.

Description

Technical Field

[0001] The utility model relates to the field of vehicle floors, and particularly relates to a vehicle floor assembly. Background Art

[0002] With the development of new energy vehicles, there are high requirements for the overall vehicle safety and lightweight performance indicators, which is convenient for increasing the cruising range and driving safety. During the later design of the vehicle body structure, it is necessary to continuously carry out topological optimization design on the vehicle body structure. In the conventional vehicle body structure of the lower body, the left and right longitudinal beams are arranged in a parallel manner and are connected by several cross beams in the middle. This vehicle body structure is not conducive to improving the bending stiffness of the vehicle body, has a short fatigue life and insufficient bending strength. During the driving process of the vehicle, abnormal noises will be generated under different road surface excitations, and the NVH performance is poor. The arrangement of this structure also makes it more difficult to design the safety during the frontal and side collisions of the vehicle, and is not conducive to the decomposition of the collision force.

[0003] Therefore, to solve the above problems, a vehicle floor assembly is needed, which can improve the NVH performance of the vehicle chassis, reduce the generation of abnormal noises during driving, and optimize the collision safety of the vehicle chassis. Summary of the Utility Model

[0004] In view of this, the purpose of the utility model is to overcome the defects in the prior art and provide a vehicle floor assembly, which can improve the NVH performance of the vehicle chassis, reduce the generation of abnormal noises during driving, and optimize the collision safety of the vehicle chassis.

[0005] The vehicle floor assembly of the utility model includes a floor body, a left wheel housing is provided on the left side of the floor body, and a right wheel housing is provided on the right side of the floor body;

[0006] It further includes a left wheel housing reinforcing beam and a right wheel housing reinforcing beam arranged on the floor body. The left wheel housing reinforcing beam is close to the joint where the left wheel housing is connected to the floor body, and the right wheel housing reinforcing beam is close to the joint where the right wheel housing is connected to the floor body.

[0007] Furthermore, a left sill beam connected to the front side of the left wheel housing and a right sill beam connected to the front side of the right wheel housing are further arranged on the floor body;

[0008] The front end of the left wheel housing reinforcing beam is connected to the left sill beam, and the front end of the right wheel housing reinforcing beam is connected to the right sill beam.

[0009] Furthermore, it further includes a local strengthening component, and the local strengthening component includes a front strengthening cross beam, a rear strengthening cross beam, a left strengthening longitudinal beam and a right strengthening longitudinal beam;

[0010] The front reinforcing cross beam and the rear reinforcing cross beam are horizontally connected to the floor body in parallel. The horizontal two ends of the front reinforcing cross beam are respectively correspondingly connected to the left wheelhouse reinforcing beam and the right wheelhouse reinforcing beam. The horizontal two ends of the rear reinforcing cross beam are respectively correspondingly connected to the left wheelhouse reinforcing beam and the right wheelhouse reinforcing beam. The front reinforcing cross beam is located on the longitudinal front side of the rear reinforcing cross beam.

[0011] The left reinforcing longitudinal beam and the right reinforcing longitudinal beam are longitudinally connected to the floor body in parallel. The longitudinal two ends of the left reinforcing longitudinal beam are respectively correspondingly connected to the front reinforcing cross beam and the rear reinforcing cross beam. The longitudinal two ends of the right reinforcing longitudinal beam are respectively correspondingly connected to the front reinforcing cross beam and the rear reinforcing cross beam. The left reinforcing longitudinal beam is located on the horizontal left side of the right reinforcing longitudinal beam.

[0012] Furthermore, the front reinforcing cross beam and the rear reinforcing cross beam are longitudinally close to the horizontal reference line passing through the longitudinal middle parts of the left wheelhouse and the right wheelhouse. The left reinforcing longitudinal beam and the right reinforcing longitudinal beam are horizontally close to the longitudinal reference line passing through the horizontal middle parts of the front reinforcing cross beam and the rear reinforcing cross beam.

[0013] Furthermore, the horizontal left end of the front reinforcing cross beam has a left reinforcing part protruding obliquely leftward from front to back, and the horizontal right end of the front reinforcing cross beam has a right reinforcing part protruding obliquely rightward from front to back.

[0014] Furthermore, the floor body includes a middle floor section and a rear floor section, and there is a height difference between the middle floor section and the rear floor section;

[0015] It further includes a left longitudinal beam middle section and a right longitudinal beam middle section arranged longitudinally in parallel on the middle floor section, and also includes a left longitudinal beam rear section and a right longitudinal beam rear section arranged longitudinally in parallel on the rear floor section;

[0016] The front reinforcing cross beam, the rear reinforcing cross beam, the left reinforcing longitudinal beam and the right reinforcing longitudinal beam are arranged on the rear floor section.

[0017] Furthermore, the left longitudinal beam middle section and the left longitudinal beam rear section are longitudinally close, and the left longitudinal beam middle section and the left longitudinal beam rear section are generally located on the same auxiliary line Ⅰ parallel to the longitudinal direction;

[0018] The right longitudinal beam middle section and the right longitudinal beam rear section are longitudinally close, and the right longitudinal beam middle section and the right longitudinal beam rear section are generally located on the same auxiliary line Ⅱ parallel to the longitudinal direction.

[0019] Furthermore, the front end of the left longitudinal beam rear section is connected to the surface where the middle floor section and the rear floor section are transitionally connected, and the rear end of the left longitudinal beam rear section is connected to the front reinforcing cross beam; the front end of the right longitudinal beam rear section is connected to the surface where the middle floor section and the rear floor section are transitionally connected, and the rear end of the right longitudinal beam rear section is connected to the front reinforcing cross beam.

[0020] Furthermore, a central channel parallel to the longitudinal direction is formed on the middle floor section.

[0021] On the rear section of the floor, a left central channel strengthening longitudinal beam and a right central channel strengthening longitudinal beam are provided. The left central channel strengthening longitudinal beam connects the left side of the central channel transversely and the front strengthening cross beam, and the right central channel strengthening longitudinal beam connects the right side of the central channel transversely and the front strengthening cross beam.

[0022] Furthermore, the left central channel strengthening longitudinal beam and the right central channel strengthening longitudinal beam are close to each other transversely. The left strengthening longitudinal beam and the right strengthening longitudinal beam are located between the middle sections of the left longitudinal beam and the right longitudinal beam, and the left central channel strengthening longitudinal beam and the right central channel strengthening longitudinal beam are located between the left strengthening longitudinal beam and the right strengthening longitudinal beam.

[0023] The beneficial effects of the present utility model are as follows: A vehicle floor assembly disclosed by the present utility model, through the left wheelhouse strengthening beam being conformally connected at the joint where the left wheelhouse is connected to the floor body, and the right wheelhouse strengthening beam being conformally connected at the joint where the right wheelhouse is connected to the floor body; through the provided left wheelhouse strengthening beam and right wheelhouse strengthening beam, it is more conducive to improving the bending stiffness of the vehicle body. Different from the general structure where the current vehicle floor assembly is not strengthened at the wheelhouse position, it improves the fatigue life of the vehicle chassis, improves the NVH performance of the vehicle chassis, can reduce the generation of driving abnormal noises, and optimizes the collision safety of the vehicle chassis. Description of the Drawings

[0024] The following further describes the present utility model in conjunction with the drawings and embodiments:

[0025] Figure 1 is a structural schematic diagram of the present utility model;

[0026] Figure 2 is a structural schematic diagram of the present utility model;

[0027] Figure 3 is a top view structural schematic diagram of the present utility model;

[0028] Figure 4 is a side view structural schematic diagram of the present utility model;

[0029] Figure 5 is through the present utility model Figure 1 A sectional structural schematic diagram of the transverse central axis of the structure. Detailed Embodiments

[0030] Figure 1This is a schematic structural diagram of the present utility model. As shown in the figure, the longitudinal direction herein refers to the length direction when this solution is assembled on a vehicle. The front corresponds to the direction from the vehicle tail to the vehicle head. The rear is in the longitudinal direction and opposite to the front direction. The transverse direction refers to the width direction when this solution is assembled on a vehicle. The left and right correspond to the left and right in the driving direction. The up and down, top and bottom, and high and low correspond to the vertical orientation when this solution is assembled on a vehicle, which will not be elaborated here. In this embodiment, the vehicle floor assembly includes a floor body. The left side of the floor body has a left wheel housing, and the right side of the floor body has a right wheel housing. This structure is consistent with the current vehicle and is relatively conventional, which will not be elaborated here.

[0031] It further includes a left wheel housing reinforcing beam 1 and a right wheel housing reinforcing beam 2 provided on the floor body. The left wheel housing reinforcing beam 1 is close to the joint where the left wheel housing is connected to the floor body, and the right wheel housing reinforcing beam 2 is close to the joint where the right wheel housing is connected to the floor body. More specifically, the left wheel housing reinforcing beam 1 is conformally connected to the joint where the left wheel housing is connected to the floor body, and the right wheel housing reinforcing beam 2 is conformally connected to the joint where the right wheel housing is connected to the floor body. By providing the left wheel housing reinforcing beam 1 and the right wheel housing reinforcing beam 2, it is more conducive to improving the bending stiffness of the vehicle body. Different from the general structure of the current vehicle floor assembly where no reinforcement is made at the wheel housing position, it improves the fatigue life of the vehicle chassis and the NVH performance of the vehicle chassis, can reduce the generation of driving abnormal noises, and optimize the collision safety of the vehicle chassis.

[0032] In this embodiment, a left sill beam 3 connected to the front side of the left wheel housing and a right sill beam 4 connected to the front side of the right wheel housing are further provided on the floor body. The front end of the left wheel housing reinforcing beam 1 is connected to the left sill beam 3, and the rear end of the left wheel housing reinforcing beam 1 is connected to the left side of the vehicle floor rear cross beam 5. The front end of the right wheel housing reinforcing beam 2 is connected to the right sill beam 4, and the rear end of the right wheel housing reinforcing beam 2 is connected to the right side of the vehicle floor rear cross beam 5. As shown in the figure, the front end of the left wheel housing reinforcing beam 1 is obliquely bent leftward from back to front and connected to the left sill beam 3, forming a continuous beam on the left side of the vehicle floor. The front end of the right wheel housing reinforcing beam 2 is obliquely bent rightward from back to front and connected to the right sill beam 4, forming a continuous beam on the right side of the vehicle floor. The projections of the left wheel housing reinforcing beam 1 and the right wheel housing reinforcing beam 2 in the height direction are in an "eight" shape. This structure is conducive to crush deformation and impact energy absorption during vehicle body collision, improving the overall vehicle safety.

[0033] In this embodiment, a local strengthening component is further included. The local strengthening component includes a front strengthening cross beam 6, a rear strengthening cross beam 7, a left strengthening longitudinal beam 8, and a right strengthening longitudinal beam 9.

[0034] The front reinforcing crossbeam 6 and the rear reinforcing crossbeam 7 are transversely connected to the floor body in parallel. The transverse two ends of the front reinforcing crossbeam 6 are respectively correspondingly connected to the left wheelhouse reinforcing beam 1 and the right wheelhouse reinforcing beam 2. The transverse two ends of the rear reinforcing crossbeam 7 are respectively correspondingly connected to the left wheelhouse reinforcing beam 1 and the right wheelhouse reinforcing beam 2. The front reinforcing crossbeam 6 is located on the longitudinal front side of the rear reinforcing crossbeam 7;

[0035] The left reinforcing longitudinal beam 8 and the right reinforcing longitudinal beam 9 are longitudinally connected to the floor body in parallel. The longitudinal two ends of the left reinforcing longitudinal beam 8 are respectively correspondingly connected to the front reinforcing crossbeam 6 and the rear reinforcing crossbeam 7. The longitudinal two ends of the right reinforcing longitudinal beam 9 are respectively correspondingly connected to the front reinforcing crossbeam 6 and the rear reinforcing crossbeam 7. The left reinforcing longitudinal beam 8 is located on the transverse left side of the right reinforcing longitudinal beam 9.

[0036] As shown in the figure, the front reinforcing crossbeam 6, the rear reinforcing crossbeam 7, the left reinforcing longitudinal beam 8 and the right reinforcing longitudinal beam 9 are connected to form a structure similar to a "well" shape; and this structure is simple and clear, which can reduce the use of body reinforcing plates, reduce the number of welding points, and reduce the manufacturing cost; at the same time, it also cooperates with the left wheelhouse reinforcing beam 1 and the right wheelhouse reinforcing beam 2, improving the body stiffness, being beneficial to the transmission and decomposition of forces during collision, and ensuring driving safety; being beneficial to the improvement of the body torsional stiffness and the reduction of stress concentration at the subframe mounting points, and improving the vehicle NVH performance.

[0037] In this embodiment, the front reinforcing crossbeam 6 and the rear reinforcing crossbeam 7 are longitudinally close to the transverse reference line passing through the longitudinal middle parts of the left wheelhouse and the right wheelhouse. The left reinforcing longitudinal beam 8 and the right reinforcing longitudinal beam 9 are transversely close to the longitudinal reference line passing through the transverse middle parts of the front reinforcing crossbeam 6 and the rear reinforcing crossbeam 7. That is, the front reinforcing crossbeam 6 and the rear reinforcing crossbeam 7 are approximately located at the longitudinal middle parts of the left and right wheelhouses, and the left reinforcing longitudinal beam 8 and the right reinforcing longitudinal beam 9 are approximately located at the transverse middle parts of the front and rear reinforcing crossbeams 7, further improving the structural compactness, meeting the structural strength requirements, and improving the vehicle NVH performance.

[0038] In this embodiment, the transverse left end of the front reinforcing crossbeam 6 has a left reinforcing part that protrudes obliquely to the left from front to back, and the transverse right end of the front reinforcing crossbeam 6 has a right reinforcing part that protrudes obliquely to the right from front to back. As shown in the figure, the transverse two ends of the front reinforcing beam protrude obliquely backward. Combining the structure that the front reinforcing crossbeam 6 and the rear reinforcing crossbeam 7 are close in the longitudinal direction, it forms an approximate enclosure of the left reinforcing longitudinal beam 8 and the right reinforcing longitudinal beam 9, further improving the structural compactness, meeting the structural strength requirements, and improving the vehicle NVH performance.

[0039] In this embodiment, the floor body includes a floor middle section 10 and a floor rear section 11, and there is a height difference between the floor middle section 10 and the floor rear section 11;

[0040] It also includes a left longitudinal beam middle section 12 and a right longitudinal beam middle section 13 arranged parallel to the longitudinal direction on the middle section 10 of the floor, and also includes a left longitudinal beam rear section 14 and a right longitudinal beam rear section 15 arranged parallel to the longitudinal direction on the rear section 11 of the floor;

[0041] The left longitudinal beam middle section 12 and the left longitudinal beam rear section 14 are close to each other longitudinally, and the left longitudinal beam middle section 12 and the left longitudinal beam rear section 14 are generally located on the same auxiliary line Ⅰ parallel to the longitudinal direction; the right longitudinal beam middle section 13 and the right longitudinal beam rear section 15 are close to each other longitudinally, and the right longitudinal beam middle section 13 and the right longitudinal beam rear section 15 are generally located on the same auxiliary line Ⅱ parallel to the longitudinal direction. After this solution is assembled on the vehicle, the height of the middle section 10 of the floor is lower than the height of the rear section 11 of the floor. The middle section 10 of the floor and the rear section 11 of the floor with a designed height difference, as well as the middle section of the longitudinal beam and the rear section of the longitudinal beam with a segmented and disconnected design, are beneficial to absorbing impact energy during a side collision of the vehicle body, and can effectively protect the safety of the battery pack or fuel tank; meeting the requirements of both lightweight and structural strength, being able to provide a reasonable force transmission channel for the collision force, and improving the collision safety. The front strengthening cross beam 6, the rear strengthening cross beam 7, the left strengthening longitudinal beam 8 and the right strengthening longitudinal beam 9 are arranged on the rear section 11 of the floor.

[0042] In this embodiment, the front end of the left longitudinal beam rear section 14 is connected to the surface where the middle section 10 of the floor and the rear section 11 of the floor are transitionally connected, and the rear end of the left longitudinal beam rear section 14 is connected to the front strengthening cross beam 6; the front end of the right longitudinal beam rear section 15 is connected to the surface where the middle section 10 of the floor and the rear section 11 of the floor are transitionally connected, and the rear end of the right longitudinal beam rear section 15 is connected to the front strengthening cross beam 6. That is, the left longitudinal beam middle section 12, the right longitudinal beam middle section 13, the left longitudinal beam rear section 14 and the right longitudinal beam rear section 15 are interconnected with the front strengthening cross beam 6, the rear strengthening cross beam 7, the left strengthening longitudinal beam 8 and the right strengthening longitudinal beam 9 in the local strengthening assembly to form a more stable force transmission system, ensuring the structural strength, being beneficial to the transmission of force during a collision, and this structure does not require other additional strengthening cross beams, meeting the force transmission requirements of the vehicle floor, and significantly reducing the weight of the vehicle chassis.

[0043] In this embodiment, a central channel 16 parallel to the longitudinal direction is formed on the middle section 10 of the floor;

[0044] A central channel left strengthening longitudinal beam 17 and a central channel right strengthening longitudinal beam 18 are arranged on the rear section 11 of the floor. The central channel left strengthening longitudinal beam 17 connects the left side of the central channel 16 transversely and the front strengthening cross beam 6, and the central channel right strengthening longitudinal beam 18 connects the right side of the central channel 16 transversely and the front strengthening cross beam 6. The central channel left strengthening longitudinal beam 17 and the central channel right strengthening longitudinal beam 18 approximately form a structure for strengthening the central channel 16, so that the central channel 16 can also be connected with each force transmission beam in this solution, further improving the structural strength of the vehicle chassis.

[0045] More specifically, the left central channel reinforcing longitudinal beam 17 and the right central channel reinforcing longitudinal beam 18 are close to each other laterally. The left reinforcing longitudinal beam 8 and the right reinforcing longitudinal beam 9 are located between the middle section 12 of the left longitudinal beam and the middle section 13 of the right longitudinal beam. The left central channel reinforcing longitudinal beam 17 and the right central channel reinforcing longitudinal beam 18 are located between the left reinforcing longitudinal beam 8 and the right reinforcing longitudinal beam 9.

[0046] As shown in the figure, the middle section 12 of the left longitudinal beam, the middle section 13 of the right longitudinal beam, the left central channel reinforcing longitudinal beam 17 and the right central channel reinforcing longitudinal beam 18 are located in the same transverse section. The left reinforcing longitudinal beam 8 and the right reinforcing longitudinal beam 9 are located in the same transverse section, and the left reinforcing longitudinal beam 8 and the right reinforcing longitudinal beam 9 are arranged at the rear longitudinally. The longitudinal beam structures in pairs are distributed in a sandwich structure. Combining with the crossbeam structure arranged perpendicular to the longitudinal beam, a reticular force transmission structure is formed, and several buffer areas can also be formed. The vehicle NVH performance is improved, and the collision energy absorption ability is excellent, which is beneficial to absorbing the impact energy and can effectively protect the safety of the battery pack or fuel tank.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A vehicle floor assembly, characterized in that: The floor body comprises a left wheel cover on the left side of the floor body and a right wheel cover on the right side of the floor body; It also includes a left wheel arch reinforcement beam and a right wheel arch reinforcement beam arranged on the floor body, the left wheel arch reinforcement beam is close to the joint where the left wheel arch is connected to the floor body, and the right wheel arch reinforcement beam is close to the joint where the right wheel arch is connected to the floor body.

2. The vehicle floor assembly according to claim 1, characterized in that: The floor body is also provided with a left sill beam connected to the front side of the left wheel housing and a right sill beam connected to the front side of the right wheel housing; A front end of the left wheel house reinforcement beam is connected to a left rocker beam, and a front end of the right wheel house reinforcement beam is connected to a right rocker beam.

3. The vehicle floor assembly according to claim 1, characterized in that: Also included is a local reinforcement assembly, the local reinforcement assembly including a front reinforcement cross beam, a rear reinforcement cross beam, a left reinforcement longitudinal beam, and a right reinforcement longitudinal beam; The front reinforcement beam and the rear reinforcement beam are connected to the floor body in parallel and in a transverse direction, the transverse ends of the front reinforcement beam are respectively connected to the left wheel house reinforcement beam and the right wheel house reinforcement beam, the transverse ends of the rear reinforcement beam are respectively connected to the left wheel house reinforcement beam and the right wheel house reinforcement beam, and the front reinforcement beam is located at the longitudinal front side of the rear reinforcement beam; The left reinforcing longitudinal beam and the right reinforcing longitudinal beam are connected to the floor body in parallel with the longitudinal direction, the longitudinal ends of the left reinforcing longitudinal beam are respectively connected to the front reinforcing cross beam and the rear reinforcing cross beam, the longitudinal ends of the right reinforcing longitudinal beam are respectively connected to the front reinforcing cross beam and the rear reinforcing cross beam, and the left reinforcing longitudinal beam is located on the lateral left side of the right reinforcing longitudinal beam.

4. The vehicle floor assembly according to claim 3, characterized in that: The front reinforcing crossbeam and the rear reinforcing crossbeam are longitudinally close to the transverse reference line of the longitudinal center of the left wheel arch and the longitudinal center of the right wheel arch, and the left reinforcing longitudinal beam and the right reinforcing longitudinal beam are transversely close to the longitudinal reference line of the transverse center of the front reinforcing crossbeam and the transverse center of the rear reinforcing crossbeam.

5. The vehicle floor assembly according to claim 3, characterized in that: The left transverse end of the front reinforcing cross beam has a left reinforcing portion protruding obliquely from front to rear to left, and the right transverse end of the front reinforcing cross beam has a right reinforcing portion protruding obliquely from front to rear to right.

6. The vehicle floor assembly according to claim 3, characterized in that: The floor body comprises a floor middle section and a floor rear section, and the floor middle section and the floor rear section have a height difference; It also includes a left longitudinal beam middle section and a right longitudinal beam middle section arranged parallel to the longitudinal direction on the middle section of the floor, and also includes a left longitudinal beam rear section and a right longitudinal beam rear section arranged parallel to the longitudinal direction on the rear section of the floor; The front reinforcing cross beam, the rear reinforcing cross beam, the left reinforcing longitudinal beam and the right reinforcing longitudinal beam are arranged on the rear section of the floor.

7. The vehicle floor assembly according to claim 6, characterized in that: The middle section of the left longitudinal beam and the rear section of the left longitudinal beam are close to each other in the longitudinal direction, and the middle section of the left longitudinal beam and the rear section of the left longitudinal beam are approximately located on the same auxiliary line I parallel to the longitudinal direction; The middle section of the right longitudinal beam and the rear section of the right longitudinal beam are close to each other in the longitudinal direction, and the middle section of the right longitudinal beam and the rear section of the right longitudinal beam are approximately located on the same auxiliary line II parallel to the longitudinal direction.

8. The vehicle floor assembly according to claim 7, characterized in that: The front end of the rear section of the left longitudinal beam is connected to the surface of the transition connection between the middle section of the floor and the rear section of the floor, and the rear end of the rear section of the left longitudinal beam is connected to the front reinforcing crossbeam; the front end of the rear section of the right longitudinal beam is connected to the surface of the transition connection between the middle section of the floor and the rear section of the floor, and the rear end of the rear section of the right longitudinal beam is connected to the front reinforcing crossbeam.

9. The vehicle floor assembly according to claim 6, characterized in that: A central channel parallel to the longitudinal direction is formed in the middle section of the floor; The rear section of the floor is provided with a left reinforcing longitudinal beam of the central channel and a right reinforcing longitudinal beam of the central channel. The left reinforcing longitudinal beam of the central channel connects the left lateral side of the central channel with the front reinforcing cross beam, and the right reinforcing longitudinal beam of the central channel connects the right lateral side of the central channel with the front reinforcing cross beam.

10. The vehicle floor assembly according to claim 9, characterized in that: The left reinforcing longitudinal beam of the central channel and the right reinforcing longitudinal beam of the central channel are close to each other in the transverse direction. The left reinforcing longitudinal beam and the right reinforcing longitudinal beam are located between the middle section of the left longitudinal beam and the middle section of the right longitudinal beam. The left reinforcing longitudinal beam of the central channel and the right reinforcing longitudinal beam of the central channel are located between the left reinforcing longitudinal beam and the right reinforcing longitudinal beam.

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