A vehicle body frame structure based on a tube beam and an integrated cast node and a forming method

Abstract

The application discloses a kind of based on tube beam and integrated casting node car body frame structure and forming method, it is related to automobile manufacturing and car body engineering technical field.The present application aims to solve the technical problems of the weight of existing automobile traditional sheet metal structure, high investment of welding die and limited structural strength.The present application provides a kind of car body frame structure, which comprises: the closed section tubular beam of multiple roots being arranged along the frame of vehicle contour, and multiple integrated node connectors being arranged at the intersection of tubular beam and connecting them into a spatial polyhedral framework.The node connector is an integrated casting node formed by using semi-solid metal die casting process and covering the end of tubular beam.The inner and outer panels of car body are fixedly connected with the frame by using non-welding connection structure.The present application significantly reduces the investment of processing equipment by using closed tube beam with high-strength die casting node and using cold connection forming process, improves the internal space of car body, and significantly enhances the torsional resistance and crashworthiness of the whole vehicle.

Description

Technical Field

[0001] This invention belongs to the field of automobile manufacturing and body engineering technology, and specifically relates to a body frame structure based on tubular beams and integrated casting nodes, as well as a method for forming the body frame structure. Background Technology

[0002] As the automotive industry accelerates its development towards new energy and lightweighting, the vehicle body structure, as a core load-bearing component, directly determines the vehicle's safety level, energy consumption, and overall rigidity. Especially for new energy vehicles, the chassis typically carries a large battery pack, significantly increasing the vehicle's weight. This necessitates that the upper body structure possess superior collision resistance, torsional rigidity, and rollover resistance while controlling weight.

[0003] Traditional automotive body structures typically employ multi-layered stamped sheet metal parts (often with open cross-sections such as "U" or "V" shapes) lapped and spot-welded to the inner and outer side panels to form hollow load-bearing beams. However, this type of structure has several limitations: First, open sheet metal parts are prone to local instability when subjected to spatial torsion and complex collision loads. To meet collision safety regulations, it is often necessary to increase the sheet metal thickness or use ultra-high-strength steel, making it difficult to reduce the body weight. Second, stamping parts require a large investment in molds, and body assembly relies on intensive resistance spot welding, resulting in complex processes and high equipment costs. Finally, sheet metal welding inevitably produces thermal deformation and heat-affected zones, leading to localized degradation of material properties.

[0004] To address these issues, the industry is gradually introducing extruded aluminum alloy profiles for use in areas such as front and rear bumper beams and door sills. Extruded aluminum profiles have closed cross-sections and are lightweight, but in the intersection areas of the vehicle body side panels and roof frames (such as A-pillar and B-pillar joints), due to the large spatial curvature and complex stress, a single extruded aluminum profile cannot meet the connection requirements of multi-dimensional joints. If traditional fusion welding is used to connect dissimilar materials (such as steel and aluminum), brittle intermetallic compounds are easily formed, resulting in insufficient connection strength and high porosity.

[0005] In summary, existing automotive body structures face technical bottlenecks in lightweight design, manufacturing cost control, and high-strength connections at spatial nodes. Developing a novel body architecture with high structural stability, strong component integration, and effective avoidance of welding heat damage is a pressing technical challenge for those skilled in the art. Summary of the Invention

[0006] To address the shortcomings of traditional sheet metal stamping and welding body construction, such as high weight, high investment in molds and welding equipment, occupation of interior space, and limited joint connection strength, this invention provides a body frame structure and forming method based on tubular beams and integrated casting joints. The aim is to reduce the development and manufacturing costs of the body while significantly improving the structural rigidity, collision safety performance, and integration of the entire vehicle.

[0007] To solve the above-mentioned technical problems, in a first aspect, the present invention provides the following technical solution:

[0008] A vehicle body frame structure based on tubular beams and integrated cast nodes includes: multiple closed-section tubular beams arranged along the side profile and roof profile of the vehicle to form a side frame and a roof frame; multiple node connectors disposed at the intersection of the closed-section tubular beams to connect adjacent closed-section tubular beams into a spatial polyhedral skeleton; wherein the node connectors are integrated cast nodes formed by a semi-solid metal die casting process, the integrated cast nodes have cavities or wrapping surfaces formed inside for accommodating the ends of the closed-section tubular beams, and the integrated cast nodes are provided with mounting structures for fixing to the inner and / or outer body panels, the mounting structures including non-welded connection structures.

[0009] By employing closed-section tubular beams instead of traditional open stamped sheet metal parts, and combining them with integrated cast joints and non-welded connection structures, this invention achieves a balance between lightweight and high rigidity. The closed-section tubular beams have a significantly increased moment of inertia compared to single-layer open sheet metal parts, enhancing rollover resistance and impact energy absorption capabilities. The semi-solid cast joints integrate tubular beams in multiple directions, reducing sheet metal overlaps, flash, and welding processes, thus reducing vehicle weight and optimizing interior space.

[0010] In a preferred embodiment of the present invention, the multiple closed-section tubular beams include: a front tubular beam of column A, a rear tubular beam of column A, a front tubular beam of column B, a rear tubular beam of column B, an upper tubular beam of column B, a lower tubular beam of column B, a front tubular beam of column C, a rear tubular beam of column C, upper tubular beams of columns AB and BC, tubular beams of columns CD, and a sill tubular beam located on one side of the perimeter; and a front tubular beam of the front crossbeam of the roof, a rear tubular beam of the front crossbeam of the roof, a second crossbeam of the roof, a third crossbeam of the roof, a fourth crossbeam of the roof, and a rear crossbeam of the roof located in the roof area. By further employing the above-mentioned fully covered tubular beam network, the present invention can construct a high-strength cage-like protective structure. The tubular beams of the side perimeter and the roof are interconnected, and in the event of a collision or top pressure, the load can be dispersed and transmitted through multiple paths, avoiding local stress concentration.

[0011] As a preferred embodiment of the present invention, the plurality of node connectors include: side panel node connectors, including upper A-pillar castings, lower A-pillar castings, upper B-pillar castings, lower B-pillar castings, upper C-pillar castings, lower C-pillar castings, upper D-pillar castings, and lower D-pillar castings; and roof node connectors, including front roof crossbeam connecting castings, second roof crossbeam connecting castings, third roof crossbeam connecting castings, and fourth roof crossbeam connecting castings. By further adopting the above-mentioned node arrangement scheme, the present invention can achieve uniform load distribution and modular assembly. The castings are arranged at the intersection of tube beams where stress is concentrated, and the adjustable thickness of the die-castings and the ability to freely arrange reinforcing ribs enhance the rigidity and stability of the vehicle body intersection area.

[0012] As a preferred embodiment of the present invention, it further includes an inner wheel arch casting and an outer wheel arch casting; the inner wheel arch casting and the outer wheel arch casting are integrally die-cast components, which are connected to the inner and / or outer side panels via self-piercing rivets, and the front end of the inner wheel arch casting is connected to the lower C-pillar casting via a flow drill screw. By further employing integrally die-cast inner and outer wheel arch castings, the present invention can achieve integration of the chassis and upper body connection area. The integrally formed wheel arch casting replaces the original scattered sheet metal parts, has good corrosion resistance, and can effectively absorb energy in the event of a side collision through a reasonable reinforcement design.

[0013] In a preferred embodiment of the present invention, the A-pillar lower casting is connected to the front A-pillar tube beam, the rear A-pillar tube beam, and the sill tube beam, respectively. The outer side of the A-pillar lower casting is connected to the side panel via bolts arranged laterally on the vehicle body, and its inner side overlaps with the tubular beam via drilled screws. Furthermore, its bottom is provided with a vertical fastening point for connecting to the front subframe of the chassis. By further employing this A-pillar lower node structure, the present invention can achieve an efficient connection between the subframe and the upper body load-bearing structure, allowing the front compartment load to be smoothly transferred to the chassis and upper body.

[0014] In a preferred embodiment of the present invention, the upper casting of the B-pillar connects to the upper tube beams of the AB-pillar, the upper tube beams of the BC-pillar, the front tube beam of the B-pillar, and the rear tube beam of the B-pillar. The outer side of the upper casting of the B-pillar is connected to the outer side panel via two layers of structural adhesive, and the inner side is connected to the inner side panel via bolts. The lower casting of the B-pillar connects to the sill tube beam, the front tube beam of the B-pillar, and the rear tube beam of the B-pillar. Its inner mounting point overlaps with the inner surface of the sill tube beam via a flow drill screw. By further employing this upper and lower B-pillar node structure, the present invention enhances the vehicle's side impact resistance. The cold-fitting and locking connection between the upper and lower casting nodes and the tube beams effectively limits the deformation during a side impact.

[0015] In a preferred embodiment of the present invention, the upper casting of the D-pillar is connected to the CD-pillar tube beam and the rear crossbeam tube beam of the roof, respectively. The outer side of the upper casting of the D-pillar is connected to the inner side panel of the vehicle body in the transverse and longitudinal directions by bolts. The lower casting of the D-pillar is connected to the CD-pillar tube beam and the lower body. The inner side of the lower casting of the D-pillar is connected to the inner side panel of the vehicle body in the transverse and longitudinal directions by flow drill screws, respectively, and its bottom surface is connected to the lower body by bolts. By further adopting a multi-directional fixed connection structure of the D-pillar node, the present invention can improve the torsional stiffness of the trunk area, strengthen the structural coordination between the lower body and the roof system, and meet the rear collision safety requirements.

[0016] In a preferred embodiment of the present invention, the closed-section tubular beam is a straight tube formed by high-strength steel plate through high-frequency welding, and then processed into a three-dimensional curved section tube through bending and hydraulic bulging processes. Positioning holes and process holes for cathodic electrophoresis are provided on the tube wall. By further employing high-frequency welding and hydraulic bulging processes, the present invention can achieve precise matching between the tubular beam and the three-dimensional vehicle body surface at a lower cost, while preserving the high yield strength of the pipe and ensuring the quality of electrophoretic corrosion protection.

[0017] To solve the above-mentioned technical problems, in a second aspect, the present invention provides the following technical solution:

[0018] A method for forming a vehicle body frame structure, used to prepare the aforementioned vehicle body frame structure, includes the following steps: Step S1, tubular beam prefabrication stage: high-strength metal sheet is formed into a closed-section tubular beam, and the geometry of the closed-section tubular beam is matched with the vehicle body contour requirements through bending and hydraulic bulging processes; Step S2, mold placement stage: the end of the prefabricated closed-section tubular beam is placed in the cavity of a die-casting mold, the shape of the cavity matching the three-dimensional shape of the node connector; Step S3, semi-solid die-casting stage: aluminum alloy is heated to... In the semi-solid temperature range, the semi-solid aluminum alloy slurry is then injected into the cavity of the die-casting mold at a preset speed and pressure; Step S4, pressure holding and cooling stage: Under pressure holding conditions, the semi-solid aluminum alloy slurry is cooled and solidified in the cavity, wrapping and bonding to the end of the closed section tubular beam. After mold opening, a spatial skeleton unit is obtained by integrating the closed section tubular beam and the node connector; Step S5, cold connection assembly stage: The assembled spatial skeleton unit is fastened to the inner and outer body panels using a non-welded connection structure.

[0019] By employing a molding method that involves pre-embedding steel pipe beams as inserts and using semi-solid aluminum alloy for die casting, this invention achieves a thermally-damaged, tight bond between dissimilar metals at the physical level. This method avoids the thermal deformation and residual thermal stress caused by fusion welding; the semi-solid aluminum alloy slurry fills smoothly, is less prone to porosity defects, improves the density of the joint, and simplifies the processing steps.

[0020] In a preferred embodiment of the present invention, in step S3, the semi-solid temperature range is set to 570°C to 590°C, and the closed-section tubular beam is subjected to surface roughening or coating with a coupling agent before being placed in the cavity. By further employing specific semi-solid temperature parameters and surface treatment steps, the present invention can reduce the thermal shock of molten aluminum to the steel pipe, preventing the steel pipe from losing strength due to high-temperature annealing; at the same time, it enhances the mechanical locking force on the ends of the steel pipe during the cooling and shrinkage of the aluminum alloy.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention introduces a tubular beam system with a closed cross section to replace single-layer stamped open sheet metal stacking, which significantly enhances the load-bearing capacity of the structure under tensile, bending and torsional conditions, and effectively ensures the occupant survival space during a collision.

[0023] 2. By connecting the pipe beams with semi-solid die-cast joints, a high degree of component integration is achieved, eliminating complex overlapping edges and a large number of welding processes, which significantly reduces the cost of mold development and welding equipment.

[0024] 3. The compact tubular and casting structure reduces the volume occupied by the cross section, thereby reducing the weight of the vehicle body and freeing up interior space.

[0025] 4. The use of cold connection technology (such as mechanical fastening and adhesive bonding) to assemble the car body eliminates the material performance degradation caused by welding thermal cycle, and improves the final assembly accuracy and production efficiency. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments disclosed in this invention, the accompanying drawings of the embodiments will be briefly described below. These drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0027] Figure 1 This is an exploded view of the installation of the vehicle body frame structure in a whole vehicle environment in Embodiment 1 of the present invention;

[0028] Figure 2 This is a three-dimensional frontal view of the vehicle frame structure in Embodiment 1 of the present invention;

[0029] Figure 3This is a schematic diagram of the vehicle frame structure in the whole vehicle environment in Embodiment 1 of the present invention;

[0030] Figure 4 This is a frontal projection view of the vehicle body side panel structure after overall assembly in Embodiment 1 of the present invention;

[0031] Figure 5 yes Figure 4 A schematic cross-sectional view of section AA in the middle;

[0032] Figure 6 yes Figure 4 Schematic diagram of the cross-section of section BB;

[0033] Figure 7 yes Figure 4 A schematic cross-sectional view of section CC;

[0034] Figure 8 yes Figure 4 A schematic cross-sectional view of section DD;

[0035] Figure 9 yes Figure 4 A schematic cross-sectional view of section EE;

[0036] Figure 10 yes Figure 4 A schematic cross-sectional view of section FF in the middle;

[0037] Figure 11 yes Figure 4 A schematic cross-sectional view of the GG section;

[0038] Figure 12 yes Figure 4 A schematic cross-sectional view of section HH;

[0039] Figure 13 yes Figure 4 Schematic diagram of the cross-section of section II;

[0040] Figure 14 yes Figure 4 A schematic cross-sectional view of section JJ in the middle;

[0041] Figure 15 yes Figure 4 A schematic cross-sectional view of section KK in the middle;

[0042] Figure 16 yes Figure 4 A schematic cross-sectional view of section LL in the middle;

[0043] Figure 17 yes Figure 4 A schematic cross-sectional view of the MM section;

[0044] Figure 18 yes Figure 4 A schematic cross-sectional view of section NN in the middle;

[0045] Figure 19 yes Figure 4 A schematic cross-sectional view of section OO;

[0046] Figure 20 yes Figure 4 A cross-sectional view of the PP section;

[0047] Figure 21 This is a process flow diagram of the molding method in Embodiment 2 of the present invention.

[0048] In the diagram: 1. Semi-solid tubular beam assembly; 1-1. Front tubular beam of A-pillar; 1-2. Rear tubular beam of A-pillar; 1-3. Front tubular beam of B-pillar; 1-4. Rear tubular beam of B-pillar; 1-5. Tubular beam installed on top of B-pillar; 1-6. Tubular beam installed below B-pillar; 1-7. Front tubular beam of C-pillar; 1-8. Rear tubular beam of C-pillar; 1-9. Tubular beam on top of AB-pillar; 1-10. Tubular beam on top of BC-pillar; 1-11. Tubular beam of CD-pillar; 1-12. Sill tubular beam; 1-13. Front tubular beam of front crossbeam of roof; 1-14. Rear tubular beam of front crossbeam of roof; 1-15. Tubular beam of second crossbeam of roof; 1-16. Tubular beam of third crossbeam of roof; 1-17. Tubular beam of fourth crossbeam of roof; 1-18. Tubular beam of rear crossbeam of roof; 1- 19. Casting on A-pillar; 1-20. Casting below A-pillar; 1-21. Casting on B-pillar; 1-22. Casting below B-pillar; 1-23. Casting on C-pillar; 1-24. Casting below C-pillar; 1-25. Casting on D-pillar; 1-26. Casting below D-pillar; 1-27. Casting connecting the front crossbeam of the roof; 1-28. Casting connecting the second crossbeam of the roof; 1-29. Casting connecting the third crossbeam of the roof; 1-30. Casting connecting the fourth crossbeam of the roof; 1-31. Casting of the inner wheel arch plate; 1-32. Casting of the outer wheel arch plate; 2. Outer side panel; 3. Inner side panel; 4. Roof assembly; 5. Bolts; 6. Drill screws; 7. Self-piercing rivets; 8. Press-fit nuts; 9. Weld nuts. Detailed Implementation

[0049] The technical solutions (including preferred technical solutions) of the present invention will be further described in detail below with reference to the accompanying drawings and by way of listing some optional embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0050] The terms used in this specification are explained as follows:

[0051] Closed-section tubular beam: refers to a structural load-bearing component in which the tube wall material itself forms a cavity. In this scheme, the preferred structure is a straight tube made by high-frequency welding and further processed to distinguish it from the incompletely closed cavity formed by spot welding and lap joint of single-layer open sheet metal parts.

[0052] Semi-solid metal casting is a molding technique that places metal between the liquidus and solidus lines (with a spherical crystalline microstructure and non-Newtonian thixotropic properties). It has low thermal shrinkage and stable filling.

[0053] One-piece overmolding: The solid component (end of the tube beam) is pre-placed in the die-casting mold, and a semi-solid metal slurry is injected to wrap the insert. After cooling and shrinkage, a tightly bonded molding process is formed.

[0054] Flow Drill Screw (FDS): A single-sided connection technology that does not require pre-drilling. It uses high-speed rotation and friction to generate heat, causing the sheet metal to plastically deform and form a bushing, which then self-taps and tightens.

[0055] Self-Piercing Rivet (SPR): A cold-joining process that uses a rivet to penetrate the upper sheet material and cause plastic deformation of the lower sheet material to lock it in place, without completely piercing the bottom surface.

[0056] Vehicle coordinate system (X / Y / Z axes): This is the standard coordinate system for automotive engineering. The X-axis refers to the vehicle's longitudinal direction (driving direction), the Y-axis refers to the vehicle's lateral direction (left and right), and the Z-axis refers to the vehicle's vertical direction (vertical height).

[0057] Example 1

[0058] This embodiment provides a vehicle body frame structure based on tubular beams and integrated cast joints, such as... Figures 1 to 20 As shown, this frame structure can effectively transfer and distribute spatial loads.

[0059] Structurally, the vehicle body frame mainly includes a semi-solid tubular beam assembly 1, an outer side panel 2, an inner side panel 3, and a roof assembly 4.

[0060] The semi-solid tubular beam assembly 1 serves as the main load-bearing framework, with all its members being closed-section tubular beams. At critical nodes where structural convergence and stress transfer occur (such as the intersection of columns), integrally cast nodes manufactured using a semi-solid process are installed. The tubular beam body is primarily composed of high-frequency welded steel pipes that have undergone hydraulic bulging and bending. Positioning holes and venting holes are provided on the pipe walls to ensure the quality of subsequent anti-corrosion electrophoresis.

[0061] The specific connection layout for each area of ​​the vehicle body is as follows:

[0062] Side panel system (taking one side as an example):

[0063] The single-sided side frame is composed of the following components: front tube beam 1-1 of column A, rear tube beam 1-2 of column A, front tube beam 1-3 of column B, rear tube beam 1-4 of column B, upper tube beam 1-5 of column B, lower tube beam 1-6 of column B, front tube beam 1-7 of column C, rear tube beam 1-8 of column C, upper tube beam 1-9 of column A and B, upper tube beam 1-10 of column B and C, tube beam 1-11 of column C and CD, and the bottom sill tube beam 1-12.

[0064] The aforementioned tubular beams are connected and anchored through specific semi-solid aluminum alloy joints. The die-cast parts on one side are categorized as follows: A-pillar upper casting 1-19, A-pillar lower casting 1-20, B-pillar upper casting 1-21, B-pillar lower casting 1-22, C-pillar upper casting 1-23, C-pillar lower casting 1-24, D-pillar upper casting 1-25, and D-pillar lower casting 1-26.

[0065] Regarding the A-pillar node area:

[0066] The A-pillar is a crucial component for resisting offset collisions (25% small offset collisions) and frontal collision load transfer. In this embodiment, the casting 1-19 on the A-pillar internally encapsulates and connects the front and rear tubular beams of the A-pillar and the tubular beams 1-9 on the AB pillars. Three mounting reference points are designed on the outer surface of the vehicle body, and the A-pillar is directly fastened to the side panel assembly 2 along the Y-direction (lateral direction) of the vehicle using bolts 5.

[0067] At the bottom, the A-pillar casting 1-20 connects upwards to the front A-pillar tube beam 1-1 and the rear A-pillar tube beam 1-2, and rearwards to the sill tube beam 1-12, serving as a crucial node for energy distribution in the front compartment. To enhance stability, the A-pillar casting 1-20 has five mounting points on its outer side, connected to the side panel outer panel via Y-direction bolts. On the inner side of the vehicle, to achieve fixation in a sealed section, the three large-area lap surfaces of the A-pillar casting 1-20 and the tube beams are reinforced with FDS6 (flow drill screws). Furthermore, the bottom of the A-pillar casting 1-20 has a reinforced mounting point, directly connected to the front subframe of the chassis using a Z-direction (vertical) long bolt; above this bottom mounting point, two mounting holes are pre-drilled for connection to the front floor tube beam, and further upwards, three FDS points connect to the front floor panel. Compared to the traditional method of spot welding sheet metal parts together, this design improves the front NVH mode through the superior stress characteristics of the solid cast aluminum nodes, and allows the impact force to be transmitted to the door sills and front floor frame through the subframe. The structure also has pre-installed mounting points for the front and rear door hinges, supporting the door's opening and closing sag stiffness.

[0068] Regarding the B-pillar node area:

[0069] The B-pillar area serves to protect the vehicle from side impacts and provides survival space in side collisions. In this embodiment, the casting 1-21 on the B-pillar connects to the top AB pillar upper tube beams 1-9, BC pillar upper tube beams 1-10, and the rear support structure of the B-pillar. Due to the limited space at the top of the B-pillar, the casting 1-21 on the B-pillar is bonded to the outer side panel assembly 2 of the vehicle body using two layers of structural adhesive (such as aerospace-grade high-strength epoxy resin adhesive), which provides both corrosion protection and sound insulation and vibration reduction. The four mounting points on the inner side of the vehicle body are connected to the inner side panel assembly 3 using Y-direction bolts, and two additional mounting points are directly Y-direction locking the top cover to the casting. In other words, due to space constraints, the outer side of the casting 1-21 on the B-pillar is connected to the outer side panel 2 using two layers of structural adhesive, while the inner side is rigidly connected to the inner side panel 3 using bolts 5.

[0070] The B-pillar casting 1-22 is fitted into the lower sill beam 1-12. The four mounting points on the outer side of the B-pillar casting 1-22 are still Y-directly locked to the outer side panel. Due to the large overlap with the inner wall of the sill beam, the inner area uses three large-faced FDS direct-drilling screws for riveting. Its upper part is rigidly fixed to the inner side panel with three Y-direction bolts, while its lower part is further anchored to the front floor casting using three Y-direction bolts. In other words, the B-pillar casting 1-22 fits tightly into the sill beam 1-12, its outer side is also secured to the outer side panel 2 with bolts 5, and the large internal overlap is drilled and riveted using three large-faced flow drill screws 6, giving the middle section of the side panel significant side impact resistance.

[0071] Regarding the node area between pillars C and D:

[0072] Casting 1-23 on the C-pillar connects to the tubular beam 1-10 on the BC-pillar and the rearward-extending piping system. Its outer side is also connected to the outer panel with two layers of structural adhesive, while its inner side is secured to the inner panel using three Y-direction bolts. The lower C-pillar casting 1-24 connects the sill and rear wheel arch area, and its inner side utilizes a three-overlap FDS fastening structure. The overlapping flanges with the inner and outer wheel arch panels are further reinforced with three Y-direction FDS bolts.

[0073] Because large SUVs or MPVs and other new energy vehicles have spacious rear cargo boxes, this invention specifically incorporates a D-pillar piping system and nodes. In addition to connecting the CD-pillar tubular beams 1-11 and the rear roof system, the castings 1-25 on the D-pillar have three fixing points on their outer side and the outer side panel. The inner side is locked to the inner side panel in a matrix configuration using bolts 5 arranged alternately in the Y and X directions, preventing the tailgate frame from twisting or deforming. The castings 1-26 below the D-pillar utilize the FDS6 fastening system, with three Y-direction and four X-direction FDS bolts on the inner side, and its bottom surface is directly anchored to the lower body base using two Z-direction thick bolts.

[0074] In other words, for the rear structure, casting 1-23 on the C-pillar supports the rearward-extending piping system, using a combination of adhesive bonding and bolts for fixation. Casting 1-25 on the D-pillar connects the CD-pillar tube beam 1-11 and the rear crossbeam of the roof, using crisscrossing multi-directional bolts 5 to lock it to the inner side panel 3. Casting 1-26 below the D-pillar uses a large area of ​​flow drill screws 6 to connect to the inner side panel 3, and the bottom surface is then anchored to the lower body with bolts 5.

[0075] Top cover and wheel arch system:

[0076] The roof frame consists of the front crossbeam (1-13), the rear crossbeam (1-14), the second crossbeam (1-15), the third crossbeam (1-16), the fourth crossbeam (1-17), and the rear crossbeam (1-18). Connecting castings for the front and second crossbeams, such as casting 1-27 and casting 1-28, are arranged at both ends of the crossbeams. These castings connect the crossbeams to the side beams using bolts and other connection structures, enhancing the lateral load-bearing capacity of the top.

[0077] At the left and right connection points of the roof area, semi-solid aluminum alloy is used to combine the crossbeam tubes with the side beams and fasten them with Y-direction bolts, thereby improving the lateral top pressure bearing capacity of the entire roof area and enabling the vehicle to perform excellently in rollover tests.

[0078] In the rear wheel arch area, there are inner wheel arch casting 1-31 and outer wheel arch casting 1-32. These two castings integrate the disparate structures and are cold-riveted to the side panel sheet metal using self-piercing rivets 7. The front end of the inner wheel arch casting 1-31 is secured to the C-pillar casting 1-24 using a flow drill screw 6. This design provides both good vibration damping performance and effective energy absorption through the crushing of the ribs during side-rear collisions.

[0079] Furthermore, to meet the assembly requirements of body accessories and interior / exterior trim parts, press-fit nuts 8 and welded nuts 9 were used at some pre-fabricated hole positions on the aforementioned tube beams and casting nodes, taking into account the local space constraints of the body. Specifically, press-fit nuts 8 (such as...) were provided on the side wall of the closed tube beam where double-sided operation was inconvenient. Figure 15 , Figure 16 (As shown in the sill beam area), while some sheet metal overlap edges or high-strength connection points requiring anti-rotation are equipped with welded nuts 9 (such as...). Figure 5 , Figure 8 As shown in the figure, this improves the overall frame's fastening and assembly system.

[0080] Example 2

[0081] This embodiment provides a method for forming a vehicle body frame structure, used to prepare the frame structure described in Embodiment 1. This method effectively avoids the strength reduction and poor bonding problems that may result from fusion welding between dissimilar metals, such as... Figure 21 As shown, the specific process steps include:

[0082] Step S1: Precast tube beam stage.

[0083] High-strength steel sheets are high-frequency welded into closed-section tubular beams. A bending and hydraulic bulging process is then used to expand the beams to fit the mold, creating a complex curved surface to match the vehicle's contours. Painting process holes are simultaneously machined into the tube walls.

[0084] Step S2: Mold placement stage (insert positioning).

[0085] For the designed "A-pillar node" and "B-pillar node," locating grooves are pre-reserved in the large die-casting machine mold to hold the ends of the prefabricated steel tubular beams. The ends of the prefabricated steel tubular beams are placed as inserts into the mold cavity of the forming node connector. Before this, the ends of the tubular beams can be roughened or coated with a coupling agent to improve the interfacial bonding force, thus effectively preventing aluminum leakage and enhancing the bonding strength.

[0086] Step S3: Semi-solid die casting stage.

[0087] An aluminum alloy with a specific ratio is heated to a semi-solid temperature range of 570°C to 590°C. At this temperature, the slurry exhibits thixotropic flow. The slurry is then injected into the mold cavity at a preset pressure and speed. Smooth laminar flow filling avoids air entrapment, and this temperature range effectively prevents the high-strength steel inserts from undergoing thermal annealing.

[0088] Step S4: Pressure holding and cooling stage.

[0089] Under pressure, the semi-solid aluminum alloy slurry cools, solidifies, and shrinks, tightly encapsulating the ends of the closed-section tubular beam. After mold opening, a spatial skeleton unit integrating the steel pipe and aluminum casting is obtained.

[0090] Step S5: Cold connection and final assembly stage. The manufactured skeleton unit is moved into the final assembly line, and the skeleton unit is physically assembled with the outer side panel 2 and the inner side panel 3 at room temperature using non-welded connection structures such as the flow drill screws 6, bolts 5, self-piercing rivets 7 and structural adhesives mentioned in Example 1.

[0091] Example 3

[0092] Based on Embodiments 1 and 2, this embodiment reasonably expands the application scenarios of the vehicle body structure. Those skilled in the art will understand that, due to the adjustability of the cast node structure, the combination of the aforementioned tubular beams and nodes can be further adapted to chassis architecture designs with separate upper and lower body sections.

[0093] When applied to a skateboard chassis equipped with an independent battery and driving system, the bottom end of the castings at the lower part of the pillars (e.g., the connecting sections of castings 1-20 under the A-pillar and the sill beams 1-12) can be adjusted to form a flange surface adapted to the skateboard chassis. During assembly, the entire passenger compartment frame is fastened to the chassis using vertically arranged high-strength bolts. In this extended solution, the high-rigidity closed bottom frame provided by this structure effectively prevents softening of the joint surface and torsional instability. Similarly, in such concealed structures with no visual impact, those skilled in the art can also reinforce local joints by means of low-heat-input cold metal transitions, which are all reasonable implementations of the technical concept described in this invention.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Those skilled in the art can make various improvements and modifications without departing from the spirit and principles of the invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A vehicle frame structure based on tubular beams and integrated cast joints, characterized in that, include: Multiple closed-section tubular beams are arranged along the side profile and roof profile of the vehicle to form a side frame and a roof frame. Multiple node connectors are provided at the intersection of the closed-section tubular beams to connect adjacent closed-section tubular beams into a spatial polyhedral skeleton. The node connector is an integral casting node formed by semi-solid metal die casting process. The integral casting node has a cavity or wrapping surface for accommodating the end of the closed cross-section tubular beam. The integral casting node is provided with an installation structure for fixing to the inner panel and / or outer panel of the vehicle body. The installation structure includes a non-welded connection structure.

2. The vehicle frame structure according to claim 1, characterized in that, The plurality of closed-section tubular beams include: The following are located on one side: the front tube beam of column A, the rear tube beam of column A, the front tube beam of column B, the rear tube beam of column B, the tube beam installed on column B, the tube beam installed below column B, the front tube beam of column C, the rear tube beam of column C, the tube beams on columns AB, the tube beams on columns BC, the tube beams on columns CD, and the sill tube beam. The top cover area includes the front crossbeam, the rear crossbeam, the second crossbeam, the third crossbeam, the fourth crossbeam, and the rear crossbeam.

3. The vehicle frame structure according to claim 2, characterized in that, The plurality of node connectors include: Side panel node connectors include upper A-pillar casting, lower A-pillar casting, upper B-pillar casting, lower B-pillar casting, upper C-pillar casting, lower C-pillar casting, upper D-pillar casting, and lower D-pillar casting; The top cover node connectors include the top cover front crossbeam connector casting, the top cover second crossbeam connector casting, the top cover third crossbeam connector casting, and the top cover fourth crossbeam connector casting.

4. The vehicle frame structure according to claim 3, characterized in that, It also includes inner wheel arch castings and outer wheel arch castings; the inner wheel arch castings and the outer wheel arch castings are integral die-cast components, which are connected to the inner side panel and / or the outer side panel by self-piercing rivets, and the front end of the inner wheel arch casting is connected to the lower C-pillar casting by a flow drill screw.

5. The vehicle frame structure according to claim 3, characterized in that, The A-pillar casting is connected to the front A-pillar tube beam, the rear A-pillar tube beam, and the sill tube beam. The outer side of the A-pillar casting is connected to the side panel by bolts arranged laterally on the vehicle body, and the inner side is connected to the tubular beam by a flow drill screw. The bottom of the casting is provided with a vertical fastening point for connecting to the front subframe of the chassis.

6. The vehicle frame structure according to claim 3, characterized in that, The castings on the B-pillar are respectively connected to the tube beams on the AB-pillar, the tube beams on the BC-pillar, the front tube beam of the B-pillar, and the rear tube beam of the B-pillar. The outer side of the castings on the B-pillar is connected to the outer side panel through two layers of structural adhesive, and the inner side of the castings on the B-pillar is connected to the inner side panel through bolts. The lower casting of the B-pillar connects to the sill tube beam, the front tube beam of the B-pillar, and the rear tube beam of the B-pillar. Its inner mounting point is connected to the inner surface of the sill tube beam by a flow drill screw.

7. The vehicle frame structure according to claim 3, characterized in that, The castings on the D-pillar are respectively connected to the tube beams of the CD-pillar and the rear cross beam tube beam of the roof. The outer side of the castings on the D-pillar is connected to the inner side panel in the transverse and longitudinal directions of the vehicle body by bolts. The lower casting of the D-pillar connects the CD-pillar tube beam and the lower vehicle body. The inner side of the lower casting of the D-pillar is connected to the inner side panel of the vehicle body in the horizontal and vertical directions by flow drill screws, and its bottom surface is connected to the lower vehicle body by bolts.

8. The vehicle frame structure according to claim 1, characterized in that, The closed-section tubular beam is a straight tube formed by high-strength steel plate through high-frequency welding, and a special-shaped cross-section tube with three-dimensional spatial curvature formed by bending and hydraulic bulging processes. The tube wall is provided with positioning holes and process holes for cathodic electrophoresis.

9. A method for forming a vehicle body frame structure, used to prepare the vehicle body frame structure according to claim 1, characterized in that, Includes the following steps: Step S1, tubular beam prefabrication stage: high-strength metal sheets are formed into closed-section tubular beams, and the geometry of the closed-section tubular beams is matched with the vehicle body contour requirements through bending and hydraulic bulging processes. Step S2, mold placement stage: Place the end of the prefabricated closed-section tubular beam into the cavity of the die-casting mold, the shape of the cavity matching the three-dimensional shape of the node connector; Step S3, Semi-solid die casting stage: The aluminum alloy is heated to the semi-solid temperature range, and then the semi-solid aluminum alloy slurry is injected into the cavity of the die casting mold at a preset speed and pressure. Step S4, Pressure Holding and Cooling Stage: Under pressure holding conditions, the semi-solid aluminum alloy slurry is cooled and solidified in the cavity, wrapping and bonding to the end of the closed section tubular beam. After mold opening, a spatial skeleton unit is obtained by integrating the closed section tubular beam and the node connector. Step S5, Cold Connection Assembly Stage: The assembled space frame unit is fastened to the inner and outer body panels using a non-welded connection structure.

10. The molding method according to claim 9, characterized in that, In step S3, the semi-solid temperature range is set to 570°C to 590°C, and the closed-section tubular beam is subjected to surface roughening or coating with coupling agent before being placed in the cavity.

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