A load-bearing structure for the underframe floor of a rail vehicle and its manufacturing method

Abstract

A rail vehicle underframe floor load-bearing structure comprises an integrated closed-cavity structure consisting of an upper plate, a middle plate, and a lower plate. The composite combination of these three plates not only increases the floor's cross-sectional area but also forms a closed-cavity load-bearing section, significantly improving overall rigidity and creating an integrated component that combines strong load-bearing capacity with lightweight advantages. The optimized floor load-bearing capacity effectively reduces the number of crossbeams and floor beams required for the underframe structure, providing crucial support for lightweight vehicle body design. Auxiliary pads fully utilize load dispersion, enhancing the safety and reliability of local structures. The hanging support components, welded to the auxiliary pads, provide stable mounting points for undercarriage equipment. A composite method combining laser welding and resistance welding replaces traditional arc welding, significantly reducing manual operation time, welding stress, and deformation, while also significantly improving production efficiency, ultimately achieving the core goals of lightweight structure, superior performance, and rapid production.

Description

Technical Field

[0001] This invention relates to the field of rail vehicle body technology, and to a steel structure adapted to the underframe floor of stainless steel urban rail vehicles, which can meet the multiple requirements of modern rail vehicles for high strength, lightweight and high efficiency. Background Technology

[0002] The steel structure of rail vehicle bodies typically includes a floor load-bearing structure. Existing subway vehicles generally employ a corrugated floor + floor beam, main crossbeam + underframe side beam design, as shown in [reference needed]. Figure 1 As shown in the diagram, this structure forms a floor frame by connecting the side beam a, the main crossbeam b, the floor beam c, and the transition connecting plate d. Then, the corrugated floor e is laid flat on top of it and welded to the base frame frame at the troughs by manual TIG or MAG welding, thus forming the base frame floor load-bearing structure.

[0003] This type of steel frame floor structure has the following inherent technical defects: First, as a thin plate component, the corrugated plate has a small moment of inertia, resulting in insufficient overall bending and torsional stiffness of the floor. During vehicle operation, it is prone to large deformation, vibration and abnormal noise. Moreover, it has many parts and a complex structure. Second, the existing chassis structure is too heavy, and the main crossbeams and floor beams are too densely arranged, which restricts the lightweight design of the vehicle body. Third, the beams and plates are mostly welded by manual arc welding, resulting in numerous welding points, a large workload, and significant stress concentration. This is not conducive to improving product dimensional accuracy and welding quality. At the same time, the complex structure also greatly hinders the improvement of production efficiency.

[0004] With the development of rail transit technology, the requirements for the comprehensive performance of trains are increasing. The existing stainless steel underframe floor load-bearing structure can no longer meet the new technical needs of the industry. There is an urgent need for a high-strength, lightweight underframe floor load-bearing structure that can help improve product precision and quality. Summary of the Invention

[0005] To address the technical problems existing in the background art, the purpose of this invention is to provide a high-strength, lightweight stainless steel base frame floor load-bearing structure for urban rail transit that is beneficial for improving product precision, quality, and production efficiency, as well as a welding method for the structure.

[0006] To achieve the above-mentioned objectives, the present invention provides a load-bearing structure for a rail vehicle underframe floor, characterized in that it includes an upper plate, a middle corrugated plate connected to the upper plate, and a lower plate connected to the middle corrugated plate, wherein the upper plate, the middle corrugated plate, and the lower plate together constitute a core load-bearing structure with a closed hollow cross section.

[0007] Furthermore, the upper panel is composed of two edge baffles and several flat floor panels connected together to form an integral upper floor assembly.

[0008] Furthermore, the middle corrugated plate is composed of two edge-closed corrugated plates and several trapezoidal corrugated plates connected together to form an integral middle corrugated floor assembly.

[0009] Furthermore, the lower plate is divided into three areas: the end traction areas and the middle equipment hoisting area. Each traction area includes an end lower floor, a pair of side lower floor panels, and a middle lower floor panel, with the pairs of side lower floor panels arranged symmetrically relative to the middle lower floor panel. The middle equipment hoisting area is further divided into three parts along the longitudinal direction, each part including a middle lower floor panel and a pair of side lower floor panels. Both the side lower floor panels and the middle lower floor panel have U-shaped weight reduction openings, and electrode passage holes are provided along the length direction at positions corresponding to the center line of the corrugated plate crest.

[0010] Furthermore, each lower layer plate is individually connected to the middle corrugated plate to form a composite structure of the middle and lower layers.

[0011] Furthermore, the edge baffle is formed by cold bending and rolling, and its edge is provided with protrusions.

[0012] Furthermore, it also includes auxiliary pads, which include a traction pad for the bolster area and a mounting pad for the mounting bracket, with the mounting bracket bearing component welded to the corresponding pad by laser welding.

[0013] A rail vehicle includes a baseboard floor support structure, characterized in that: the baseboard floor support structure is any one of the above-mentioned baseboard floor support structures.

[0014] Another object of the invention is to provide a method for manufacturing the above-mentioned rail vehicle underframe floor load-bearing structure, characterized by comprising the following steps: 1. First, the electrodes of several lower plates are positioned corresponding to the center line of the crest of the middle corrugated plate through holes, and the lower plates are individually connected to the middle corrugated plate one by one by intermittent laser welding to form a middle and lower composite structure. 2. Then, the upper plate and the middle corrugated plate are fixedly connected by resistance spot welding through the pre-reserved electrode holes on the lower plate to form an integrated closed cavity base frame floor structure of upper, middle and lower layers; after the overall cavity structure is formed, the auxiliary pad is welded to the lower surface of the lower plate by laser welding. 3. Finally, the support bracket is welded and fixed to the corresponding auxiliary pad by laser welding to form a complete base frame floor support structure.

[0015] The design principle of this invention is based on a hollow cavity structure and a reinforcing rib structure as the core design concept. The hollow cavity and internal reinforcing ribs are mainly achieved through a sandwich structure formed by a middle corrugated plate. According to the principles of mechanics of materials, the bending resistance of a component is positively correlated with the distance of the material from the neutral axis; the farther the distance from the neutral axis, the higher the bending efficiency of the material. This invention uses an upper plate, a middle corrugated plate, and a lower plate to form a closed hollow cross section, concentrating the effective material at the upper and lower outer edges of the cross section to maximize the bending efficiency of the material. At the same time, the continuous wave structure of the corrugated plate itself serves as internal reinforcing ribs, significantly reducing material usage while ensuring the overall rigidity and strength of the structure, thus achieving the goal of lightweight design. In terms of welding technology, laser welding is used to achieve reliable connection of multiple layers of stainless steel plates. This process has the advantages of high welding efficiency, low heat input, and small welding deformation, which can significantly improve structural stability and product quality. The combination of the above design and process constitutes the core technology of this invention for improving floor rigidity, enhancing load-bearing strength, and achieving lightweight design.

[0016] 1. Excellent structural load-bearing performance: This invention employs a closed-cavity underframe floor load-bearing structure composed of upper, middle, and lower layers. The structure is evenly distributed, effectively dispersing various loads acting on the floor, while providing greater flexibility for the layout and installation of under-vehicle equipment. When subjected to vertical loads, this closed-cavity underframe floor load-bearing structure, with its excellent vertical stiffness, can effectively transfer the load and prevent excessive deformation; when subjected to longitudinal loads, it can effectively disperse concentrated longitudinal loads, avoiding localized stress concentration problems.

[0017] 2. Achieve lightweight vehicle body design: The three-layer composite structure design replaces the traditional single corrugated floor and load-bearing beam structure, which greatly improves the overall rigidity of the floor and can significantly reduce the number of redundant main crossbeams and floor beams, effectively reducing the overall weight of the chassis and providing strong support for the weight reduction of the whole vehicle.

[0018] 3. Simplified production and improved efficiency: This invention uses long cold-formed steel sections and large plates as the structural basis, which greatly reduces the number of parts in the base frame floor; it adopts a welding process that combines laser welding and spot welding to replace traditional manual arc welding, which not only reduces the amount of manual work and production links, and lowers energy consumption and production costs, but also greatly reduces welding deformation and improves the dimensional accuracy of the product due to the reduced welding heat input; at the same time, the automated welding operation greatly improves the production efficiency of the product. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the existing steel structure of the base frame floor; Figure 2 This is a schematic diagram of the overall structure of the present invention; Figure 3 These are cross-sectional views of the structure and welding diagrams of the present invention; Figure 3-1 This is a schematic diagram of resistance spot welding between the upper and middle layers; Figure 3-2 This is a schematic diagram of laser welding between the lower and middle layers; Figure 3-3 This is a schematic diagram of laser welding between the lower plate and the backing plate; Figure 3-4 This is a schematic diagram of laser welding between the auxiliary pad and the hanger support component; Figure 4 This is a schematic diagram of the upper plate of the present invention; Figure 5 This is a schematic diagram of the middle corrugated plate of the present invention; Figure 6 This is a schematic diagram of the lower layer plate of the present invention; Figure 7 This is a schematic diagram of the auxiliary pad of the present invention.

[0020] In the diagram: 1. Upper plate; 101. Edge baffle; 102. Side floor; 103. Middle floor; 2. Middle corrugated plate; 201. Edge corrugated plate; 202. First transition corrugated plate; 203. Second transition corrugated plate; 204. Middle corrugated plate; 3. Lower plate; 301. Second middle lower floor; 302. Third opposite side lower floor; 303. First middle lower floor; 304. Second opposite side lower floor; 305. Middle lower floor; 306. First opposite side lower floor; 307. End lower floor; 308. Third middle lower floor; 309. Fourth opposite side lower floor; 310. Fifth opposite side lower floor; 4. Auxiliary pad; 401. Pad for traction area; 402. Mounting bracket pad; 5. Hanging bracket support; 6. Resistance spot welding; 7. First laser welding; 8. Second laser welding; 9. Third laser welding. Detailed Implementation

[0021] Reference Figure 2 , Figure 3 , Figures 3-1 to 3-4 The stainless steel subway vehicle underframe floor support structure of the present invention mainly consists of an upper plate 1, a middle corrugated plate 2, a lower plate 3, an auxiliary pad 4, and a lifting support component 5. The upper plate 1 and the middle corrugated plate 2 are fixedly connected by resistance spot welding 6, and the middle corrugated plate 2 and the lower plate 3 are fixedly connected by a first laser welding 7. The three components work together to form a closed cavity core structure. The lower plate 3 and the auxiliary pad 4 are fixedly connected by a second laser welding 8, and the auxiliary pad 4 and the lifting support component 5 are fixedly connected by a third laser welding 9, forming a complete underframe floor support structure with lifting function.

[0022] Reference Figure 4The upper panel 1 includes two edge baffles 101, two side panels 102, and one center panel 103. These five panels are made of austenitic stainless steel SUS301L-ST and are joined together by four continuous laser welds to form an integrated upper panel assembly with an overlap width of 30-40mm. The edge baffles 101 are cold-bent and rolled, with rectangular protrusions along their edges. These protrusions serve two purposes: firstly, to block water flow in the concealed passenger compartment door area of ​​the subway car, and secondly, to connect with the interior floor.

[0023] Reference Figure 5 The middle corrugated plate 2 includes two edge corrugated floor plates 201, two first transition corrugated plates 202, two second transition corrugated plates 203, and one intermediate corrugated floor plate 204. The corrugated plates are made of austenitic stainless steel SUS301L-MT, with a trapezoidal wave structure in cross-section. The peaks and troughs are flat, the total height is within 60mm, the plate thickness is within 0.8mm, and the wave spacing is between 100-150mm. All corrugated plates are cold-bent and rolled. Each corrugated plate is a continuous structure. The longitudinal edges of adjacent corrugated plates overlap to form an lap structure with an overlap width of 30-40mm. Seven corrugated plates are continuously welded together along the lap edges using laser welding to form a single corrugated plate.

[0024] Reference Figure 6 The lower plate 3 is longitudinally divided into three areas: the end support areas and the middle equipment hoisting area. The right support area includes an end lower floor 307, a first pair of side lower floor 306, and a middle lower floor 305. The left support area includes an end lower floor 307, a fifth pair of side lower floor 310, and a middle lower floor 305. The first pair of side lower floor 306 and the fifth pair of side lower floor 310 are symmetrically arranged relative to the middle lower floor 305. The middle equipment hoisting area is larger and longitudinally divided into three parallel parts, each 3-4 meters long. The third middle lower floor 308 and the fourth pair of side lower floor 309 constitute one part. The second intermediate lower floor 301 and the third pair of side lower floor 302 are part of one section, and the first intermediate lower floor 303 and the second pair of side lower floor 304 are part of another section. All the side lower floor and intermediate lower floor are provided with U-shaped weight reduction openings, and circular electrode through holes with a diameter of 30mm are provided along the length direction at the position corresponding to the center line of the corrugated plate 2 of the middle layer, for use in resistance spot welding. Each piece of the lower plate 3 is a flat plate structure, made of austenitic stainless steel SUS301L-ST material. Each piece of the lower plate 3 is connected to the middle corrugated plate 2 by laser welding, and the pieces of the lower plate 3 are not connected to each other.

[0025] The three-vertical-row, five-horizontal-row arrangement of the lower plate is designed primarily based on the functions of each area of ​​the underframe and the width of the steel plates. The three longitudinal rows maximize the utilization of the steel plate width, and this three-row design ensures structural symmetry and stress balance on both sides of the underframe. The five transverse rows distribute the underframe into two parts: the bogie area and the suspension equipment area (three parts). Another major advantage of this modular layout is that dividing the underframe into sections according to different load-bearing areas facilitates both production and processing, and allows for interchangeability between different vehicle models.

[0026] Reference Figure 7 The auxiliary pad 4 includes pads 401 for the bolster areas at both ends and pads 402 for mounting brackets. The pads in the bolster area are shaped based on the outer contour of the bolster beam with a machining allowance. The pads in the traction beam area are longitudinally rectangular and fit the outer contour of the traction beam. The dimensions of the mounting bracket bearing pad 402 in the middle area of ​​the underframe are based on the mounting bracket, with appropriate welding allowances at the outer contour. The auxiliary pads are mainly used to distribute local loads. For the bolster area, they can disperse the impact load of the bogie, avoiding stress concentration. Similarly, the pads above the mounting brackets also distribute the equipment load, reducing the burden on the load-bearing welds, increasing local stiffness, reducing the amplitude of equipment vibration, and improving the safety factor of the welds.

[0027] The specific assembly process of the floor structure of the present invention is as follows: First, the lower layer board 3 is welded to the middle layer corrugated board 2 one by one by intermittent laser welding to form a middle and lower layer composite structure; then, the lower layer board 1 is precisely positioned by the electrode through the hole reserved on the lower layer board 3, and the upper layer board 1 and the middle layer corrugated board 2 are fixedly connected by resistance spot welding to form a closed cavity floor core structure integrating the upper, middle and lower layers; after the overall cavity structure is formed, various reinforcing pads are laser welded to the lower surface of the lower layer board 3, and finally the hanging bracket bearing 5 is laser welded to the corresponding auxiliary pad 4 to form a complete base frame floor steel structure.

Claims

1. A load-bearing structure for the underframe floor of a rail vehicle, characterized in that, It includes an upper plate (1), a middle corrugated plate (2) connected to the upper plate (1), and a lower plate (3) connected to the middle corrugated plate (2). The upper plate (1), the middle corrugated plate (2), and the lower plate (3) together constitute the core load-bearing structure with a closed hollow cross section.

2. The load-bearing structure for a rail vehicle underframe floor according to claim 1, characterized in that, The upper panel (1) is composed of two edge baffles (101), two side floor panels (102), and a middle floor panel (103) connected together to form an integral upper floor assembly.

3. The load-bearing structure for a rail vehicle underframe floor according to claim 1, characterized in that, The middle corrugated board (3) is composed of two edge-closed corrugated boards (301), two first transition corrugated boards (202), two second transition corrugated boards (203) and a middle corrugated board (204) connected together to form an integral middle corrugated floor assembly.

4. The load-bearing structure for a rail vehicle underframe floor according to claim 1, characterized in that, The lower plate (3) is longitudinally divided into three regions: the end traction areas and the middle equipment hoisting area; each traction area includes an end lower floor (307), a pair of side lower floors and a middle lower floor (305), and the pair of side lower floors are symmetrically arranged relative to the middle lower floor (305); the middle equipment hoisting area is further divided into three parts along the longitudinal direction, each part including a middle lower floor and a pair of side lower floors; all the side lower floors and the middle lower floor are provided with U-shaped weight reduction openings, and electrode through holes are provided along the length direction at the position corresponding to the center line of the crest of the middle corrugated plate (2).

5. The load-bearing structure for a rail vehicle underframe floor according to claim 4, characterized in that, The lower layer plate (3) is individually connected to the middle layer corrugated plate (2) to form a composite structure of the middle and lower layers.

6. The load-bearing structure for a rail vehicle underframe floor according to claim 2, characterized in that, The edge baffle (101) is formed by cold bending and rolling, and its edge is provided with protrusions.

7. The load-bearing structure for a rail vehicle underframe floor according to claim 1, characterized in that, It also includes an auxiliary pad (4), the auxiliary floor including a bolster area pad (401) and a mounting bracket pad (402), and the mounting bracket support (5) is welded to the corresponding pad by laser welding.

8. A rail vehicle, comprising a base frame floor load-bearing structure, characterized in that: The base frame floor support structure is any one of the base frame floor support structures described in claims 1-7.

9. A method for manufacturing a rail vehicle underframe floor load-bearing structure according to any one of claims 1-7, characterized in that... Includes the following steps: (1) First, the electrodes of the lower plate (3) are positioned corresponding to the center line of the crest of the middle corrugated plate (2) through the holes. Then, the lower plate (3) and the middle corrugated plate (2) are individually welded together by intermittent laser welding to form a middle and lower composite structure. (2) The electrode through the reserved holes on the lower plate (3) is used for precise positioning. The upper plate (1) and the middle corrugated plate (2) are fixedly connected by resistance spot welding to form an integrated closed cavity base frame floor structure of upper, middle and lower layers. After the overall cavity structure is formed, the auxiliary pad (4) is welded to the lower surface of the lower plate (3) by laser welding. (3) Finally, the hanging bracket (5) and the corresponding auxiliary pad (4) are welded and fixed by laser welding to form a complete base frame floor support structure.

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