Structure of low-floor vehicle

Abstract

The utility model provides a kind of structure of low floor vehicle, comprising: bottom plate, rear door sill assembly and floor framework, bottom plate is installed on floor framework;Rear door sill assembly is installed in floor framework tail portion, and it is connected with bottom plate;Floor framework includes two parallelly arranged longitudinal beam assembly and the crossbeam subassembly connected between two longitudinal beam assembly;Each longitudinal beam assembly includes the front longitudinal beam, first middle longitudinal beam, second middle longitudinal beam and rear longitudinal beam that are sequentially connected, and the height difference is formed between the upper surface of front longitudinal beam and the upper surface of first middle longitudinal beam, and the height difference is formed between the upper surface of second middle longitudinal beam and the upper surface of first middle longitudinal beam, so that front longitudinal beam, first middle longitudinal beam and second middle longitudinal beam are in ladder shape;Bottom plate is ladder-shaped along the length direction of each longitudinal beam assembly.The front longitudinal beam, first middle longitudinal beam, second middle longitudinal beam form the ladder-shaped downlink structure extending from the front part of vehicle to the rear part of vehicle, so that the ground clearance of the bottom plate of the rear part of vehicle is reduced, and the convenience and work efficiency of loading and unloading goods are improved.

Description

Technical Field

[0001] This utility model relates to the field of vehicle mechanical structure technology, and specifically to a structure for a low-floor vehicle. Background Technology

[0002] The car body is the core structural component of a vehicle, and it is divided into three categories: non-load-bearing, load-bearing, and semi-load-bearing. Among them, the load-bearing body integrates the frame and the body shell to form a floor skeleton, which is lightweight and highly stable. To ensure the load-bearing strength and collision safety performance of the body structure, vehicles using load-bearing bodies typically maintain a high and relatively straight spatial shape along the longitudinal direction of the floor skeleton to meet the layout requirements of components such as the powertrain, driveshaft, and exhaust system. Therefore, the overall structural height of the chassis of traditional load-bearing bodies is high, resulting in a high floor height in the cargo box, which affects the convenience of passengers getting on and off the vehicle and the utilization rate of interior space. Especially for trucks, the floor height in the cargo box is closely related to the efficiency and safety of loading and unloading for freight personnel, and is one of the key factors affecting the convenience of loading and unloading for freight personnel.

[0003] Therefore, a vehicle structure with a low floor height inside the carriage is needed to improve the convenience of loading and unloading for freight personnel. Utility Model Content

[0004] One of the objectives of this utility model is to provide a structure for a low-floor vehicle to solve the problem in the prior art where the insufficient ground clearance of the truck floor makes loading and unloading cargo inconvenient for freight personnel.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A low-floor vehicle structure includes: a floor plate, a rear sill assembly, and a floor frame, wherein the floor plate is mounted on the floor frame; the rear sill assembly is mounted at the rear of the floor frame and connected to the floor plate; the floor frame includes two longitudinal beam assemblies and a crossbeam assembly, the two longitudinal beam assemblies being arranged in parallel, and the crossbeam assembly connecting the two longitudinal beam assemblies; each longitudinal beam assembly includes a front longitudinal beam, a first middle longitudinal beam, a second middle longitudinal beam, and a rear longitudinal beam connected sequentially, with a height difference between the upper surface of the front longitudinal beam and the upper surface of the first middle longitudinal beam, and a height difference between the upper surface of the second middle longitudinal beam and the upper surface of the first middle longitudinal beam, so that the front longitudinal beam, the first middle longitudinal beam, and the second middle longitudinal beam are stepped; the floor plate is stepped along the length direction of each longitudinal beam assembly.

[0006] According to the above-mentioned technical means, the front longitudinal beam, the first middle longitudinal beam, and the second middle longitudinal beam in the floor frame can form a stepped downward structure extending from the front of the vehicle to the rear of the vehicle. The floor plate installed on the floor frame can also descend in a stepped manner towards the rear of the vehicle, thereby reducing the ground clearance of the rear floor plate of the vehicle, reducing the height of freight personnel loading and unloading goods from the cargo compartment, and further improving the convenience and work efficiency of freight personnel loading and unloading goods.

[0007] Furthermore, each of the longitudinal beam assemblies also includes a first transition beam, through which the front longitudinal beam and the first middle longitudinal beam are connected.

[0008] Based on the above technical means, the first transition beam can make the front longitudinal beam and the first middle longitudinal beam transition smoothly and continuously, avoiding the interface abrupt change caused by the direct connection between the front longitudinal beam and the first middle longitudinal beam, which helps to reduce stress concentration and ensure the strength of the connection between the front longitudinal beam and the first middle longitudinal beam.

[0009] Furthermore, the front longitudinal beam includes a first sheet metal and a second sheet metal, which are interlocked; one end of the first sheet metal and the second sheet metal overlaps on the first transition beam.

[0010] According to the above technical means, the first sheet metal and the second sheet metal are interlocked to form a box-shaped interface, which improves the bending strength and torsional stiffness of the front longitudinal beam; the first sheet metal and the second sheet metal overlap on the first transition beam to form a multi-point two-section structure, which helps to ensure the connection strength between the front longitudinal beam and the first transition beam.

[0011] Furthermore, each of the longitudinal beam assemblies also includes a second transition beam, through which the first middle longitudinal beam and the second middle longitudinal beam are connected.

[0012] Based on the aforementioned technical means, the second transition beam enables a smooth and continuous transition between the first and second longitudinal beams, avoiding abrupt changes in cross-section at the connection between the first and second longitudinal beams, reducing stress concentration, and ensuring the strength of the connection between the first and second longitudinal beams.

[0013] Furthermore, the first transition beam, the first central longitudinal beam, the second transition beam, and the second central longitudinal beam are integrally formed.

[0014] Based on the above technical means, integral molding enables continuous and smooth force transmission between the first transition beam, the first central longitudinal beam, the second transition beam, and the second central longitudinal beam, avoiding the risk of stress concentration or connection failure at the connection interface of adjacent components, and is conducive to forming a high-strength integral beam.

[0015] Furthermore, the cross-sections of the first transition beam, the first middle longitudinal beam, the second transition beam, the second middle longitudinal beam, and the rear longitudinal beam are all "U" shaped.

[0016] According to the above technical means, the "几"-shaped cross section is a reinforced cross section, its unique shape features high strength, and the "几"-shaped cross section can reduce the usage of materials on the premise of ensuring structural strength, featuring light weight and economic efficiency.

[0017] Further, the rear threshold assembly includes a door frame outer panel, a threshold body and a door frame inner panel, the door frame outer panel is mounted at the tail of the floor frame; one side edge of the threshold body is mounted on the door frame outer panel; the two opposite side edges of the door frame inner panel are respectively connected to one side edge of the door frame outer panel and one side edge of the threshold body.

[0018] According to the above technical means, the door frame outer panel, the door frame inner panel and the threshold body are connected to form a closed frame structure covering the tail of the vehicle body, and the door frame outer panel is connected to the floor frame at the same time, which ensures a rigid connection between the rear threshold assembly and the floor frame; the threshold body is a force-bearing structure that directly carries cargo or occupants, and the door frame outer panel and the door frame inner panel provide support for the threshold body.

[0019] Further, the threshold body includes a first threshold sheet metal part, a second threshold sheet metal part and a transition sheet metal part, one side edge of the first threshold sheet metal part is mounted on the door frame outer panel; the second threshold sheet metal part is mounted on the door frame inner panel and forms a height difference with the first threshold sheet metal part; the two opposite side edges of the transition sheet metal part are respectively connected to the first threshold sheet metal part and the second threshold sheet metal part.

[0020] According to the above technical means, the height difference design between the first threshold sheet metal part and the second threshold sheet metal part can reduce the rear height of the rear threshold assembly, facilitate cargo handlers to lift cargo when loading, lower the unloading height, and reduce the risk of cargo damage and personal safety risks; the transition sheet metal part provides a smooth and continuous transition for the connection of the first threshold sheet metal part and the second threshold sheet metal part, effectively ensuring the bending resistance and deformation resistance of the threshold body.

[0021] Further, the first threshold sheet metal part, the second threshold sheet metal part and the transition sheet metal part are integrally formed.

[0022] According to the above technical means, the integral forming eliminates the weak stress phenomenon at the connection positions of the first threshold sheet metal part, the second threshold sheet metal part and the transition sheet metal part, and improves the structural strength of the threshold body; at the same time, the production method of integral forming is simple and efficient.

[0023] Further, a bumper mounting bracket is also included, and the bumper mounting bracket is mounted on the rear threshold assembly for mounting a bumper.

[0024] According to the above technical means, the bumper mounting bracket provides a mounting base for the bumper, ensuring that the bumper is stably mounted on the rear threshold assembly.

[0025] The beneficial effects of this utility model are as follows: The front longitudinal beam, the first middle longitudinal beam, and the second middle longitudinal beam in the floor frame can form a stepped downward structure extending from the front of the vehicle to the rear. The floor plate installed on the floor frame can also descend in a stepped manner towards the rear of the vehicle, thereby reducing the ground clearance of the rear floor plate of the vehicle, reducing the height of freight personnel loading and unloading goods from the cargo compartment, and further improving the convenience and work efficiency of freight personnel loading and unloading goods. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a side view of the overall structure of this utility model.

[0028] Figure 2 This is a three-dimensional structural diagram of the rear door sill assembly of this utility model installed on the floor frame; Figure 3 This is a side view of the rear door sill assembly of this utility model installed on the floor frame; Figure 4 This is a structural schematic diagram of the rear door sill assembly of this utility model; Figure 5 This is a top view of the rear door sill assembly of this utility model installed on the floor frame; Figure 6 yes Figure 5 Schematic diagram of the FF section at the middle and rear door sill assembly; Figure 7 This is a schematic diagram of the front longitudinal beam of this utility model; Figure 8 yes Figure 5 Schematic diagram of section AA; Figure 9 yes Figure 5 Schematic diagram of the BB section; Figure 10 yes Figure 5 Schematic diagram of the C-section; Figure 11 yes Figure 5 Schematic diagram of the DD section; Figure 12 yes Figure 5 Schematic diagram of the EE section; Figure 13 This is one of the structural schematic diagrams of the bridge with a two-stage drop in the embodiment; Figure 14 This is a second schematic diagram and a partial sectional view of the structure of the bridge with a two-stage drop in the embodiment. Figure 15 This is a schematic diagram of the structure in the embodiment where the leaf springs and shock absorbers are arranged under the floor frame; Figure 16 This is a schematic diagram of the steel leaf spring in the embodiment.

[0029] in, 100. Base plate; 200. Rear sill assembly; 210. Door frame outer panel; 220. Sill body; 221. First sill sheet metal; 222. Second sill sheet metal; 223. Transition sheet metal; 230. Door frame inner panel; 300. Floor frame; 310. Longitudinal beam assembly; 311. Front longitudinal beam; 3111. First sheet metal; 3112. Second sheet metal; 312. First middle longitudinal beam; 313. Second middle longitudinal beam; 314. Rear longitudinal beam; 315. 316. Second transition beam; 321. Crossbeam 1; 322. Crossbeam 2; 323. Crossbeam 3; 324. Crossbeam 4; 325. Crossbeam 5; 326. Crossbeam 6; 327. Crossbeam 7; 330. Buffer block assembly; 400. Bumper mounting bracket; 500. Secondary drop rear axle; 510. Axle head assembly; 520. U-bolt; 600. Leaf spring; 610. Front chuck; 620. Rear chuck; 700. Shock absorber. Detailed Implementation

[0030] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. The drawings are for illustrative purposes only and should not be construed as limiting the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0031] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0032] This embodiment provides, as follows: Figures 1 to 16The structure of a low-floor vehicle shown includes: a floor plate 100, a rear sill assembly 200, and a floor frame 300. The floor plate 100 is mounted on the floor frame 300; the rear sill assembly 200 is mounted at the rear of the floor frame 300 and connected to the floor plate 100; the floor frame 300 includes two longitudinal beam assemblies 310 and a crossbeam assembly, the two longitudinal beam assemblies 310 being arranged in parallel, and the crossbeam assembly connecting the two longitudinal beam assemblies 310; each longitudinal beam assembly 31... The 0 includes a front longitudinal beam 311, a first middle longitudinal beam 312, a second middle longitudinal beam 313, and a rear longitudinal beam 314 connected in sequence. There is a height difference between the upper surface of the front longitudinal beam 311 and the upper surface of the first middle longitudinal beam 312, and there is a height difference between the upper surface of the second middle longitudinal beam 313 and the upper surface of the first middle longitudinal beam 312, so that the front longitudinal beam 311, the first middle longitudinal beam 312, and the second middle longitudinal beam 313 are stepped. The bottom plate 100 is stepped along the length direction of each longitudinal beam assembly 310.

[0033] The front longitudinal beam 311, the first middle longitudinal beam 312, and the second middle longitudinal beam 313 in the floor frame 300 can form a stepped downward structure extending from the front of the vehicle to the rear. The floor plate 100 installed on the floor frame 300 can also descend in a stepped manner towards the rear of the vehicle, thereby reducing the ground clearance of the rear floor plate 100 of the vehicle, reducing the height at which freight personnel can load and unload goods from the cargo compartment, and further improving the convenience and work efficiency of freight personnel loading and unloading goods.

[0034] Specifically, the height difference between the upper surface of the front longitudinal beam 311 and the upper surface of the first middle longitudinal beam 312 is approximately 100 mm (with an allowable error of ±5 mm), and the height difference between the upper surface of the first middle longitudinal beam 312 and the upper surface of the second middle longitudinal beam 313 is approximately 50 mm (again, with an allowable error of ±5 mm).

[0035] To facilitate wheel arrangement, the two parallel longitudinal beam assemblies 310 are curved at the center of the rear wheel, and the total width of the curved part of the two assemblies is about 30mm narrower than the front and rear ends of the two longitudinal beam assemblies 310.

[0036] The base plate 100 is fixed to the floor frame 300 by welding or screwing.

[0037] like Figure 3 As shown, in this embodiment, each longitudinal beam assembly 310 further includes a first transition beam 315, through which the front longitudinal beam 311 and the first middle longitudinal beam 312 are connected. The first transition beam 315 enables a smooth and continuous transition between the front longitudinal beam 311 and the first middle longitudinal beam 312, avoiding abrupt interface changes caused by direct connection between the front longitudinal beam 311 and the first middle longitudinal beam 312. This helps reduce stress concentration and ensures the strength of the connection between the front longitudinal beam 311 and the first middle longitudinal beam 312.

[0038] like Figure 7As shown, in this embodiment, the front side member 311 includes a first sheet metal part 3111 and a second sheet metal part 3112, which are snap-fitted to each other; one end of each of the first sheet metal part 3111 and the second sheet metal part 3112 is lapped on the first transition beam 315. The first sheet metal part 3111 and the second sheet metal part 3112 are snap-fitted to form a box-shaped interface, which improves the bending strength and torsional rigidity of the front side member 311; the first sheet metal part 3111 and the second sheet metal part 3112 are lapped on the first transition beam 315 to form a multi-point and two-section connection, which is beneficial to ensuring the connection strength between the front side member 311 and the first transition beam 315.

[0039] As Figure 3 As shown, in this embodiment, each side member assembly 310 further includes a second transition beam 316, and the first middle side member 312 and the second middle side member 313 are transitionally connected via the second transition beam 316. The second transition beam 316 enables a smooth and continuous transition between the first middle side member 312 and the second middle side member 313, avoids sudden section changes at the connection between the first middle side member 312 and the second middle side member 313, reduces stress concentration, and ensures the connection strength between the first middle side member 312 and the second middle side member 313.

[0040] In this embodiment, the first transition beam 315, the first middle side member 312, the second transition beam 316 and the second middle side member 313 are integrally formed. The integral forming enables continuous and smooth force transmission among the first transition beam 315, the first middle side member 312, the second transition beam 316 and the second middle side member 313, avoids the risk of stress concentration or connection failure at the connection interface of adjacent components, and is conducive to forming a high-strength integral beam.

[0041] In this embodiment, the cross sections of the first transition beam 315, the first middle side member 312, the second transition beam 316, the second middle side member 313 and the rear side member 314 are all in a "several" shape. The "several"-shaped cross section is a reinforced cross section, whose unique shape features high strength, and the "several"-shaped cross section can reduce the material consumption on the premise of ensuring the structural strength, featuring lightweight and economical properties.

[0042] Specifically, Figure 5 the cross-sectional shape of each side member assembly 310 in Figures 8 to 12 As shown, a variable cross-section side member is adopted, wherein the section A-A of the front side member 311 is a closed box-shaped section, the depth of section B-B is greater than that of section C-C, and from section C-C to section D-D to section E-E, the section height decreases gradually. The variable cross-section design of the vehicle body side member reserves sufficient installation and movement space for other chassis components, ensuring the normal operation of other chassis parts.

[0043] As Figure 2As shown, the cross beam assembly includes a first cross beam 321, a second cross beam 322, a third cross beam 323, a fourth cross beam 324, a fifth cross beam 325, a sixth cross beam 326 and a seventh cross beam 327. Each cross beam also has a "几"-shaped cross section. Cross beams with different section heights are used, and the cross beam assembly is arranged according to the longitudinal beam assembly 310.

[0044] As Figure 4 and Figure 6 shown, in this embodiment, the rear sill assembly 200 includes a door frame outer panel 210, a sill body 220 and a door frame inner panel 230. The door frame outer panel 210 is mounted at the tail of the floor frame 300; one side edge of the sill body 220 is mounted on the door frame outer panel 210; the two opposite side edges of the door frame inner panel 230 are respectively connected to one side edge of the door frame outer panel 210 and one side edge of the sill body 220. The door frame outer panel 210, the door frame inner panel 230 and the sill body 220 are connected to form a closed frame structure covering the tail of the vehicle body. At the same time, the door frame outer panel 210 is connected to the floor frame 300, which ensures a rigid connection between the rear sill assembly 200 and the floor frame 300; the sill body 220 is a force-bearing structure that directly carries cargo or occupants, and the door frame outer panel 210 and the door frame inner panel 230 provide support for the sill body 220.

[0045] As Figure 4 and Figure 6 shown, in this embodiment, the sill body 220 includes a first sill sheet metal part 221, a second sill sheet metal part 222 and a transition sheet metal part 223. One side edge of the first sill sheet metal part 221 is mounted on the door frame outer panel 210; the second sill sheet metal part 222 is mounted on the door frame inner panel 230 and forms a height difference with the first sill sheet metal part 221; the two opposite side edges of the transition sheet metal part 223 are respectively connected to the first sill sheet metal part 221 and the second sill sheet metal part 222. The height difference design between the first sill sheet metal part 221 and the second sill sheet metal part 222 can reduce the rear height of the rear sill assembly 200, and further reduce the sill height of the cargo box on the truck, so as to facilitate the lifting of cargo by freight personnel during loading, reduce the unloading height, and lower the risk of cargo damage and personal safety risk; the transition sheet metal part 223 provides a smooth and continuous transition for the connection between the first sill sheet metal part 221 and the second sill sheet metal part 222, which effectively ensures the bending resistance and deformation resistance of the sill body 220.

[0046] In this embodiment, the first sill sheet metal part 221, the second sill sheet metal part 222 and the transition sheet metal part 223 are integrally formed. The integral forming eliminates the stress weak phenomenon at the connection positions of the first sill sheet metal part 221, the second sill sheet metal part 222 and the transition sheet metal part 223, and improves the structural strength of the sill body 220; at the same time, the integral forming production method is simple and efficient.

[0047] As Figure 4 and Figure 6As shown, this embodiment also includes a bumper mounting bracket 400, which is mounted on the rear sill assembly 200 for mounting the bumper. The bumper mounting bracket 400 provides a mounting base for the bumper, ensuring that the bumper is securely mounted on the rear sill assembly 200.

[0048] When the rear sill assembly 200 is assembled onto the truck, the overall ground clearance of the rear sill assembly 200 is greater than that of the bumper mounting bracket 400, and the left and right ends of the sill body 220 (the two ends arranged along the width direction of the vehicle) are welded or screwed onto the base plate 100 and the bumper, and the first sill sheet metal 221 is fixed to the carpet in the truck bed by a buckle.

[0049] When the chassis structure of this embodiment is applied to a vehicle, other vehicle components can also be arranged as follows: 1. Adopting such Figure 14 The secondary drop rear axle 500 shown has a rear axle tube with the middle section lower than the two sides by about 70mm. The two axle head assemblies 510 of the secondary drop rear axle 500 are located on the outside of the rear longitudinal beam 314 and are connected to the wheels.

[0050] 2. For example Figures 13 to 16 As shown, the rear leaf spring 600 is positioned above the axle tube of the two-stage drop rear axle 500. The two-stage drop rear axle 500 is equipped with U-bolts 520 for fixing the leaf spring 600. To limit the extreme runout of the leaf spring 600, a buffer block assembly 330 is installed on the longitudinal beam assembly 310 above the leaf spring 600. The buffer block assembly 330 forms a safe buffer support mechanism. Furthermore, the buffer block assembly 330 is staggered with the leaf spring 600 to ensure the stability of the two-stage drop rear axle 500. The rear suspension system adopts a combination layout of a few-leaf spring 600, flat lugs and obliquely mounted shock absorbers 700, which effectively reduces the rear overhang height and further reduces the vehicle floor height; the front lugs 610 of the few-leaf spring 600 are placed outside the longitudinal beam assembly 310, and the rear lugs 620 are installed at the end of the variable cross-section longitudinal beam assembly 310. The height of the longitudinal beam assembly 310 is relatively low here, which ensures the movement space of the few-leaf spring 600 while reducing the height of the few-leaf spring 600.

[0051] 3. The vehicle adopts a front-engine, front-wheel-drive configuration, with no drive mechanism under the rear floor, which helps to reduce the ground clearance of the middle and rear sections of the vehicle floor.

[0052] 4. The use of a load-bearing body structure eliminates the gap between the floor and the floor frame 300, which helps to reduce the floor height.

[0053] 5. The long wheelbase and short rear overhang design of the vehicle ensures a safe departure angle while reducing the vehicle's floor clearance.

[0054] By optimizing the layout of the vehicle components as described above, the ground clearance of the vehicle floor can be reduced to 500mm, improving the convenience and efficiency of loading and unloading for freight personnel.

[0055] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A structure for a low-floor vehicle, characterized in that, comprising: a floor panel (100), a rear threshold assembly (200) and a floor frame (300), wherein the floor panel (100) is mounted on the floor frame (300); the rear threshold assembly (200) is mounted at the tail of the floor frame (300) and connected to the floor panel (100); the floor frame (300) comprises two side member assemblies (310) and a cross member assembly, the two side member assemblies (310) are arranged in parallel, and the cross member assembly is connected between the two side member assemblies (310); each of the side member assemblies (310) comprises a front side member (311), a first middle side member (312), a second middle side member (313) and a rear side member (314) connected in sequence, a height difference is formed between the upper surface of the front side member (311) and the upper surface of the first middle side member (312), and a height difference is formed between the upper surface of the second middle side member (313) and the upper surface of the first middle side member (312), so that the front side member (311), the first middle side member (312) and the second middle side member (313) are in a stepped shape; the floor panel (100) is in a stepped shape along the length direction of each of the side member assemblies (310).

2. The structure of a low-floor vehicle according to claim 1, characterized in that, each of the side member assemblies (310) further comprises a first transition beam (315), and the front side member (311) and the first middle side member (312) are transitionally connected through the first transition beam (315).

3. The structure of a low-floor vehicle according to claim 2, characterized in that, the front side member (311) comprises a first sheet metal part (3111) and a second sheet metal part (3112), and the first sheet metal part (3111) and the second sheet metal part (3112) are fastened to each other; one end of each of the first sheet metal part (3111) and the second sheet metal part (3112) is lapped on the first transition beam (315).

4. The structure of a low-floor vehicle according to claim 2, characterized in that, each of the side member assemblies (310) further comprises a second transition beam (316), and the first middle side member (312) and the second middle side member (313) are transitionally connected through the second transition beam (316).

5. The structure of a low-floor vehicle according to claim 4, characterized in that, the first transition beam (315), the first middle side member (312), the second transition beam (316) and the second middle side member (313) are integrally formed.

6. The structure of a low-floor vehicle according to claim 5, characterized in that, the cross sections of the first transition beam (315), the first middle side member (312), the second transition beam (316), the second middle side member (313) and the rear side member (314) are all in a shape of the Chinese character "几".

7. The structure of a low-floor vehicle according to claim 1, characterized in that, the rear threshold assembly (200) comprises a door frame outer panel (210), a threshold body (220) and a door frame inner panel (230), wherein the door frame outer panel (210) is mounted at the tail of the floor frame (300); one side edge of the threshold body (220) is mounted on the door frame outer panel (210); two opposite side edges of the door frame inner panel (230) are respectively connected to one side edge of the door frame outer panel (210) and one side edge of the threshold body (220).

8. The structure of a low-floor vehicle according to claim 7, characterized in that, The threshold body (220) includes a first threshold sheet metal (221), a second threshold sheet metal (222), and a transition sheet metal (223). One side of the first threshold sheet metal (221) is installed on the outer panel (210) of the door frame. The second threshold sheet metal (222) is installed on the inner panel (230) of the door frame and forms a height difference with the first threshold sheet metal (221). The two opposite sides of the transition sheet metal (223) are respectively connected to the first threshold sheet metal (221) and the second threshold sheet metal (222).

9. The structure of a low-floor vehicle according to claim 8, characterized in that, The first threshold sheet metal (221), the second threshold sheet metal (222), and the transition sheet metal (223) are integrally formed.

10. The structure of a low-floor vehicle according to claim 1, characterized in that, It also includes a bumper mounting bracket (400) which is mounted on the rear sill assembly (200) for mounting the bumper.

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