Power battery rolling steel lower box body, forming method and vehicle

Abstract

The invention relates to the field of structural design of lower box bodies of new energy automobile power battery packs, in particular to a power battery rolling steel lower box body, a forming method and a vehicle, and the power battery rolling steel lower box body comprises a box body frame, a mounting assembly, a heat management assembly, a structure sealing assembly, a connecting assembly and a bottom protection plate assembly; the box body frame comprises an internal frame and a frame external coating structure, and the internal frame and the frame external coating structure are connected and integrated through rivet nuts; the hanging assembly is arranged on the side portion and / or the front end of the box body frame and connected with the inner frame in a spot welding mode. The bottom protection plate assembly is connected with the mounting assembly and the box body frame through bolts to form a Y-direction anti-extrusion strengthening structure; wherein the inner frame is formed by splicing and welding four sections of rolling profiles with the same cross section, and each section of rolling profile is provided with a plurality of cutting holes used for weight reduction and spot welding avoidance. The sealing performance can be improved, the structural strength is improved, and the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of lower housing structure design for power battery packs in new energy vehicles, and more specifically, to a roll-formed steel lower housing for power batteries, a forming method, and a vehicle. Background Technology

[0002] With the development of the new energy industry and the gradual reduction and eventual elimination of subsidies, steel, as an alternative material, is increasingly becoming a key solution for OEMs and battery manufacturers, driven by cost reduction. The design and forming method of the roll-formed steel lower housing for power batteries has become a critical technology attracting significant attention from major automakers and battery manufacturers. Currently, the design and forming of the roll-formed steel lower housing for power batteries faces the following problems: Welding corrosion: Steel is less resistant to corrosion than aluminum, especially at the arc weld seam, which is very susceptible to corrosion even after electrophoretic treatment.

[0003] Sealing failure: Because the wall thickness of the roll-pressed steel casing of the power battery is relatively thin, arc welding is often prone to burn-through, leading to sealing failure.

[0004] Poor mechanical strength: The box wall is thinner under roll forming, making it impossible to achieve local reinforcement.

[0005] High mold opening cost: Rolled profiles have many different cross-sectional types, resulting in high mold opening costs.

[0006] High manufacturing cost: The sealing surface requires laser welding, which is costly. Summary of the Invention

[0007] The purpose of this invention is to provide a roll-formed steel lower housing for power batteries, which can solve at least one technical problem existing in the prior art to a certain extent.

[0008] The technical solution of this invention is implemented as follows: A roll-formed steel lower housing for a power battery includes a housing frame, a mounting assembly, a thermal management assembly, a structural sealing assembly, a connecting assembly, and a bottom protective plate assembly. The box frame includes an inner frame and an outer frame covering structure, and the inner frame and the outer frame covering structure are connected and integrated by rivets and nuts; The mounting component is disposed on the side and / or front end of the box frame and is connected to the internal frame by spot welding. The bottom protective plate assembly is connected to the mounting assembly and the box frame by bolts to form a Y-direction anti-compression reinforced structure; The internal frame is made of four sections of roll-formed profiles with the same cross-section welded together. Each section of roll-formed profile has multiple cutting holes for weight reduction and spot welding avoidance.

[0009] Furthermore, the internal frame also includes crossbeams, longitudinal beams, and reinforcing plates disposed inside the frame, wherein the crossbeams, longitudinal beams, and reinforcing plates are all made of steel and are connected to the roll-formed profile by welding.

[0010] Furthermore, the roll-formed profile has a H-shaped or I-shaped cross section, is made of steel, has a wall thickness of 0.8–1.2 mm, a cross section width of 25–35 mm, and a height of 95–115 mm; The diameter of the cutting holes is 20–25 mm, and the spacing is 70–90 mm.

[0011] Furthermore, the mounting component extends into the inner side of the internal frame and is spot-welded through a pre-set through hole on the inner wall of the internal frame to avoid exposing the arc weld seam.

[0012] Furthermore, the mounting assembly includes a left mounting assembly, a right mounting assembly, and a front mounting assembly, wherein the left mounting plate, right mounting plate, upper mounting plate, and lower mounting plate are all high-strength steel stamped parts, and mounting plates of the same type are common mold parts.

[0013] Furthermore, the mounting sleeve is made of steel or aluminum alloy and is fixed to the mounting plate by welding, pressing or gluing.

[0014] Furthermore, the bottom protective plate assembly includes a bottom protective plate body, a mounting reinforcement, a high-strength structural adhesive, and a bottom protective layer; The mounting reinforcement is positioned above the bottom protective plate body, and the gaps are filled with high-strength structural adhesive to enhance the overall rigidity.

[0015] Furthermore, the thermal management component is a water-cooled plate, which is connected to the lower side of the internal frame by a pop rivet; The lower side of the internal frame is provided with alternating blind rivet openings and rivet nut openings. The diameter of the blind rivet openings is 5–6 mm and the spacing is 80–90 mm.

[0016] A method for forming the roll-formed steel lower housing of a power battery includes the following steps: S1. Roll forming four profiles with the same cross-section, and then cutting them by length, resulting in the first profile, the second profile, the third profile, and the fourth profile; S2. Machining pre-drilled holes for rivet nuts, pre-drilled holes for blind rivets, and spot welding clearance holes on various profiles; S3. The four profile sections are laser-welded together to form a closed-loop frame, creating a frame assembly; S4. Weld the crossbeams, longitudinal beams, and reinforcing plates to the inside of the frame assembly to form an internal frame; S5. The steel plate is cut and bent to serve as the external covering structure of the frame, and connected to the internal frame by rivet nuts to form a box frame; S6. Place the mounting component inside the housing frame and connect it to the internal frame by spot welding; S7. Connect the thermal management component to the lower side of the housing frame using blind rivets; S8. Connect the bottom protective plate assembly to the mounting assembly, the thermal management assembly, and the housing frame respectively using bolts to complete the integration; In step S2, the spot welding clearance holes also serve a weight reduction function, with a hole diameter of 20–25 mm and a spacing of 70–90 mm; in step S6, the spot welding operation is located inside the box frame to avoid corrosion and sealing failure caused by external arc welding.

[0017] A vehicle includes the aforementioned roll-formed steel lower housing for a power battery, wherein the lower housing is installed at the bottom of the vehicle body as a load-bearing structure for the battery pack and is used to accommodate and fix the battery cell modules.

[0018] Compared with the prior art, the beneficial effects of the present invention are: In this application, the box frame adopts a split-type + internal and external composite structure design. The internal frame and the external covering structure are integrated by riveting nuts to form a closed cavity, which significantly improves the sealing performance and separates the functions of "structural load-bearing" and "sealing protection", thus optimizing the manufacturing logic. The connection between the mounting components and the box frame is made by spot welding instead of traditional arc welding. The welding position can be located on the inside of the box and can be operated through the spot welding avoidance holes on the profile. Its advantages are: low heat input and no risk of weld burn-through; the weld points are shielded by the internal structure, effectively isolating the corrosive environment and solving the problem of weld corrosion. The bottom guard plate component adopts integrated integration and local reinforcement. Both left and right mounting components can be integrated with the bottom guard plate by bolt connection to form a more rigid side structure. This local reinforcement structure can be flexibly designed according to the safety requirements of the whole vehicle, realizing reinforcement as needed, weight reduction and cost reduction. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of the roll-formed steel lower housing of the power battery of the present invention; Figure 2 This is another structural schematic diagram of the roll-formed steel lower housing of the power battery of the present invention; Figure 3 This is an exploded view of the roll-formed steel lower housing of the power battery of the present invention; Figure 4 This is an exploded view of the box frame of the present invention; Figure 5 This is an assembly drawing of the box frame of the present invention; Figure 6 This is a schematic diagram of the structure of the mounting component of the present invention; Figure 7 This is an integrated diagram of the bottom protective plate assembly of the present invention; Figure 8 This is an exploded view of the bottom protective plate assembly of the present invention.

[0021] In the picture: 100 - Enclosure frame; 200 - Mounting assembly; 300 - Thermal management assembly; 400 - Structural sealing assembly; 500 - Connection assembly; 600 - Bottom protection plate assembly; 110 - Internal frame; 111 - Frame assembly; 111a - First profile section; 111b - Second profile section; 111c - Third profile section; 111d - Fourth profile section; 112 - Internal reinforcement assembly; 120 - External frame covering structure; 210 - Left mount component; 220 - Right mount component; 230 - Front mount component; 610 - Bottom protective plate body; 620 - Mounting reinforcement; 630 - High-strength structural adhesive; 640 - Bottom protective layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0025] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0029] like Figures 1 to 8 As shown, this application provides a novel roll-formed steel lower housing for power batteries and its forming method, and further provides a vehicle including the battery pack. The lower housing system, through structural innovation and process optimization, effectively solves the problems of welding corrosion, sealing failure, poor mechanical strength, and high mold costs existing in existing steel lower housings.

[0030] Example 1: A Rolled Steel Lower Housing System for Power Batteries Please see Figures 1 to 3 This embodiment discloses a roll-formed steel lower housing for a power battery, including: a housing frame 100, a mounting assembly 200, a thermal management assembly 300, a structural sealing assembly 400, a connecting assembly 500, and a bottom protective plate assembly 600.

[0031] The box frame 100 serves as the main load-bearing structure of the entire lower box. It adopts a split composite design and consists of an internal frame 110 and an outer frame cladding structure 120.

[0032] Please refer to Figure 4 and Figure 5 , the internal frame 110 includes a border component 111 and an internal reinforcement component 112. The border component 111 is formed by welding four identical "eye-shaped" cross-section rolled profiles, namely the first profile 111a, the second profile 111b, the third profile 111c, and the fourth profile 111d. The cross-section width of each profile is 25 mm, the height is 110 mm, the wall thickness is 0.8 mm, and the material is high-strength cold-rolled steel. The four profiles have exactly the same cross-sectional shape, are common-mode parts, and can be used universally on different vehicle platforms, significantly reducing the mold development cost.

[0033] A plurality of cutting holes are arranged at intervals along the length direction of each profile, serving as spot welding avoidance holes and weight reduction holes. In this embodiment, the diameter of the cutting holes is 22 mm, and the spacing is 80 mm. These holes not only achieve lightweight design but also provide operating space for the inner side spot welding of the subsequent mounting component 200.

[0034] The internal reinforcement component 112 includes multiple cross beams, longitudinal beams, and several reinforcement plates. The cross beams and longitudinal beams adopt a "square-shaped" cross-section and are formed by rolling process. The material is steel, the cross-section width is 20 mm, the height is 85 mm, and the wall thickness is 0.8 mm. The reinforcement plates are formed by stamping process, and the material is steel with a wall thickness of 0.8 mm. All internal reinforcement parts are fixed inside the border component 111 by welding to enhance the overall stiffness and torsional resistance.

[0035] The outer frame cladding structure 120 is formed by cutting, bending, and welding a whole piece of steel plate, which is wrapped outside the internal frame 110 to form a closed cavity, playing a role in enhancing the sealing performance and local reinforcement. The internal frame 110 and the outer frame cladding structure 120 are integrally connected by screwing through multiple rivet nuts. In this embodiment, a rivet nut installation opening is reserved on the lower side of the border component 111, with an opening diameter of 7.5 mm and a spacing of 85 mm.

[0036] In addition, a blind rivet opening is also reserved on the lower side of the border component 111 for connecting the thermal management component 300. The diameter of the blind rivet opening is 5.5 mm, the spacing is 85 mm, and it is distributed alternately with the rivet nut opening to avoid stress concentration.

[0037] Please continue to refer to Figure 3 and Figure 6The mounting assembly 200 includes a left mounting assembly 210, a right mounting assembly 220, and a front mounting assembly 230, which are used to fix the battery pack to the longitudinal beams or transverse beams of the vehicle body, respectively.

[0038] The left mounting assembly 210 includes a left mounting plate and a mounting sleeve. Similarly, the right mounting assembly 220 includes a right mounting plate and a mounting sleeve. The front mounting assembly 230 includes an upper mounting plate, a lower mounting plate, and a mounting sleeve. It should be noted that, for ease of distinction, these three mounting sleeves can be referred to as the first mounting sleeve, the second mounting sleeve, and the third mounting sleeve, respectively.

[0039] The left and right mounting plates are made of high-strength steel with a thickness of 1.5mm and are formed by stamping. They are common mold parts. The upper and lower mounting plates are also high-strength steel stamped parts with a thickness of 1.5mm and are also common mold parts, which improves the interchangeability of parts.

[0040] The mounting sleeve is used to receive bolts at the vehicle body end for fastening. In this embodiment, the mounting sleeve is machined from steel and fixed to the corresponding mounting plate by welding. In other embodiments, the mounting sleeve may also be made of aluminum alloy, formed by die casting or machining, and connected to the mounting plate by press-fitting or structural adhesive bonding. All mounting sleeves on the mounting components 200 are of the same specification, facilitating assembly management.

[0041] Crucially, the mounting component 200 is connected to the housing frame 100 by spot welding, with the welding point located inside the housing and operated through cutting holes in the profile. This design avoids the risk of "weld burn-through" caused by excessive heat input in traditional arc welding. At the same time, the weld point is shielded by the internal structure, effectively isolating it from external corrosive environments, significantly improving the durability and sealing reliability of the connection.

[0042] Please continue reading. Figure 3 In this embodiment, the thermal management component 300 is a water-cooled plate used to cool the battery module. The water-cooled plate is connected to the bottom of the housing frame 100 by multiple blind rivets. Compared with the traditional FDS (FlowDrill Screw) connection method, blind rivets do not require pre-drilling, making them particularly suitable for high-strength steel materials. This solves the problem of difficult connection of FDS on high-strength steel, while also reducing fastener costs and equipment investment.

[0043] The bottom protective plate assembly 600, as shown Figure 7 and Figure 8 As shown, it includes a bottom protective plate body 610, a mounting reinforcement 620, a high-strength structural adhesive 630, and a bottom protective layer 640.

[0044] The bottom guard plate body 610 is made of high-strength steel material with a thickness of 0.8 mm and is formed by stamping process; in other embodiments, hot-formed ultra-high-strength steel can also be selected to further improve the impact resistance. Multiple sleeve mounting structure holes are provided on the bottom guard plate body 610.

[0045] The mounting reinforcement 620 is also provided with matching structure holes. During installation, the mounting reinforcement 620 is placed above the bottom guard plate body 610, and its bottom surface is completely fitted with the upper surface of the bottom guard plate. Subsequently, the mounting sleeve passes through the structure holes of both and is fixed.

[0046] The high-strength structural adhesive 630 uses a foaming structural adhesive, which is filled in the gap between the mounting reinforcements 620. During the curing process, the colloid expands and tightly fills the voids, not only enhancing the connection strength, but also playing a role in buffering, sound insulation and anti-corrosion.

[0047] The bottom guard plate assembly 600 is connected to the thermal management component 300, the box body frame 100 and the left and right mounting components (210, 220) through bolts to achieve multi-point connection. In particular, the bottom guard plate assembly 600 is directly connected to the left and right mounting components (210, 220) through bolts, forming a more rigid integrated side structure, significantly improving the anti-extrusion ability and collision safety of the battery pack in the Y direction (lateral direction).

[0048] Generally speaking: The power battery roll-formed steel lower box body (or lower box body system) provided by this solution consists of six core components: box body frame 100, mounting component 200, thermal management component 300 (such as a water-cooled plate), structural sealing component 400, connection component 500, bottom guard plate component 600; (1) Box body frame 100: Split + internal and external composite structure Internal frame 110: It is formed by welding four identical "eye-shaped" or "sun-shaped" roll-formed profiles (the first profile 111a - the fourth profile 111d) to form the main bearing frame.

[0049] The cross-sections of the four profiles are exactly the same and are common-mode parts, which greatly improves the die reuse rate and reduces the die opening cost.

[0050] Cutting holes (i.e., "spot welding avoidance holes") are provided on the profiles, with a spacing of 70 - 90 mm and a diameter of 20 - 25 mm, which have the dual functions of weight reduction and reserving operation space for internal spot welding. <op

[0051] Internal strengthening components 112 (cross beams, longitudinal beams, strengthening plates) are integrated inside the frame by welding to improve the overall stiffness.

[0052] Frame external cladding structure 120: It is formed by cutting, bending and welding a steel plate, which is wrapped outside the internal frame 110.

[0053] The internal frame 110 and the external covering structure are integrated by means of rivet nuts to form a closed cavity, which significantly improves the sealing performance.

[0054] This design separates the functions of "structural load-bearing" from "sealing and protection," thus optimizing the manufacturing logic.

[0055] (2) Mounting component 200: Independent molding + common mold design It includes three mounting components 200: left, right, and front, which are used to connect to the vehicle body.

[0056] Mounting components 200 (such as left / right mounting plates) are stamped separately from the housing frame and manufactured separately from the frame.

[0057] The mounting plate is made of high-strength steel stamping, with a thickness of 1.0-2.0mm, and has high strength.

[0058] The left and right mounting plates, as well as the top and bottom mounting plates, are all common mold parts, further improving versatility.

[0059] The mounting sleeve on the mounting component 200 can be connected to the mounting plate by welding, crimping or gluing, and the material can be steel or aluminum.

[0060] (3) Innovation of key connection methods Mounting component 200 is connected to housing frame 100: Spot welding is used instead of traditional arc welding. The welding position is located inside the housing and is performed through clearance holes in the profile.

[0061] Advantages: Low heat input, no risk of burn-through; the weld joint is shielded by the internal structure, effectively isolating the corrosive environment and solving the problem of weld corrosion.

[0062] Thermal management component 300 (water-cooled plate) is connected to the housing frame 100: It uses blind rivets for connection, with a spacing of 80-90mm and an opening diameter of 5-6mm.

[0063] Advantages: Compared to FDS (flow drill screws), no pre-drilling is required, which solves the problem of difficult connection of high-strength steel FDS, and the cost is lower.

[0064] Rivet nut openings: used to connect external covering structures, and are distributed alternately with the openings of blind rivets to optimize stress distribution.

[0065] (4) Bottom plate assembly 600: Integrated and locally reinforced It includes a bottom protective plate body 610, a mounting reinforcement 620, a high-strength structural adhesive 630, and a bottom protective layer 640.

[0066] Bottom guard plate body 610: It is stamped from high-strength steel or hot-formed ultra-high-strength steel, with a thickness of 0.8 - 1.5 mm.

[0067] The key innovation is that the left and right mounting components 220 and the bottom guard plate are integrally integrated by bolt connection, forming a side structure with stronger rigidity. A mounting reinforcement 620 is set between the mounting component 200 and the bottom guard plate, and the gap is filled with foamed high-strength structural adhesive 630 to achieve multi-level reinforcement. This local reinforcement structure can be flexibly designed according to the vehicle safety requirements to achieve reinforcement as needed, weight reduction, and cost reduction.

[0068] Embodiment 2: A forming method for a roll-pressed steel lower box body of a power battery This embodiment provides a forming method for the above roll-pressed steel lower box body of a power battery, including the following steps: S1: Frame roll-pressed profile forming Using a continuous roll-pressing process, the steel coil is processed into a long profile with a "mesh-shaped" cross-section, and the self-closure strength of the profile is ensured by high-frequency welding.

[0069] S2: Profile length cutting According to the requirements of the pre-designed drawing, the long profile is cut into four sections of frame profiles with specified lengths, corresponding to the first section of profile 111a, the second section of profile 111b, the third section of profile 111c, and the fourth section of profile 111d respectively.

[0070] S3: Profile mounting hole cutting On each section of the profile, the following holes are laser-cut at the predetermined positions: Riveting pre-opening holes (for subsequent connection of the external cladding structure); Blind rivet pre-opening holes (for connecting the water-cooled plate); Spot welding avoidance holes (i.e., cutting holes 113, for spot welding inside the mounting component 200).

[0071] S4: Frame component 111 welding ' The four sections of profiles are arranged in a rectangular layout, and their ends are spliced by laser welding technology to form a complete frame component 111.

[0072] S5: Inner frame 110 forming Internal reinforcement members such as cross beams, longitudinal beams, and reinforcement plates are welded to the inside of the frame component 111 according to the designed positions to complete the manufacture of the inner frame 110.

[0073] S6: External seal forming The steel plate used to make the external cladding structure 120 of the frame is cut and bent to form the required three-dimensional shape.

[0074] S7: Box frame 100 forming The formed frame outer covering structure 120 is fitted onto the outside of the inner frame 110 and fixedly connected to the inner frame 110 by rivet nuts, thus completing the assembly of the box frame 100.

[0075] S8: Mount component 200 connection Position the left mounting component 210, right mounting component 220, and front mounting component 230 to their respective positions on the housing frame 100, and spot weld the overlapping area of ​​the mounting component 200 and the frame component 111 through the cutting holes inside the housing.

[0076] S9: Thermal Management Component 300 Connection Place the water-cooled plate at the bottom of the enclosure frame 100, and use a pop rivet to rivet the water-cooled plate to the enclosure frame 100 through the preset pop rivet opening.

[0077] S10: Connection of bottom protective plate assembly 600 to the main structure The bottom protective plate assembly 600 is placed below the water-cooled plate and connected to the water-cooled plate and the housing frame 100 by bolts.

[0078] S11: Connection between bottom guard plate assembly 600 and mounting assembly 200 The bottom guard plate assembly 600 is connected to the left and right mounting assemblies (210, 220) by bolts to achieve integrated side panel design.

[0079] S12: Assembly Completed After all assembly processes are completed, the entire box undergoes airtightness testing, visual inspection, and dimensional verification to obtain the finished power battery roll-pressed steel lower box.

[0080] Example 3: A vehicle This embodiment provides a vehicle, including a body and a battery pack mounted on the bottom of the body. The battery pack includes the power battery roll-formed steel lower housing system described in any of the above embodiments. Due to the adoption of the lower housing structure of this application, the vehicle significantly reduces manufacturing costs and enhances product competitiveness while ensuring the safety of the battery system.

[0081] Alternative implementation methods: Those skilled in the art will understand that various modifications and substitutions can be made to the above embodiments without departing from the spirit and scope of this application. For example: The cross-sectional shape of the roll-formed profile can be "H-shaped" or other reinforced cross-sections; The spot welding connection can be replaced by laser spot welding or resistance spot welding; The arrangement of the mounting reinforcement 620 can be adjusted according to actual stress requirements, such as adopting a grid-like, ring-shaped, or partially stacked design. The high-strength structural adhesive 630 can be replaced with a non-foaming structural adhesive, but foaming adhesives have advantages in terms of filling and cushioning.

[0082] This application proposes a complete three-in-one technical system of "modular split design + novel connection technology + local reinforcement structure", specifically: 1. Box frame 100 design – double-layer composite structure, its structural composition is as follows: Internal frame 110: welded together from frame component 111 and internal reinforcing component 112; External frame covering structure 120: A steel plate is cut, bent and welded and wrapped around the outside of the inner frame; Frame material: steel, with a Z-shaped or M-shaped cross section, 25–35 mm wide, 95–115 mm high, and 0.8–1.2 mm thick; Reinforcing beam: U-shaped cross section, roll-formed or bent, wall thickness 0.8–1.0 mm; External cladding structure: steel plate stamping / bending, wall thickness 0.8–1.0 mm.

[0083] Innovation Highlights: The internal and external structures are integrated by bolting with rivets and nuts, avoiding welding and thus preventing corrosion in the heat-affected zone. The external covering structure forms a continuous sealing layer, which significantly improves the overall sealing performance. The internal frame 110 is manufactured independently → supports modular production.

[0084] 2. Frame Component 111 Design – Four-section common mold material + opening for weight reduction: The frame is constructed by welding together four sections of rolled profiles (section 111a to section 111d) to form a rectangular frame. All profiles have the same cross-section, making it a common mold component. This greatly improves the platform's versatility, making it suitable for various battery pack sizes and significantly reducing mold development costs.

[0085] Opening design (multi-functional hole): 1. The rivet nut opening is located on the lower side, φ7–8mm, with a spacing of 80–90mm, and is used to connect the external covering structure; 2. The pop rivet opening is located on the lower side, φ5–6mm, with a spacing of 80–90mm, for connecting the thermal management assembly 300 (water-cooled plate). 3. Spot welding clearance holes, located on the profile body, φ20–25mm, with a spacing of 70–90mm, can reduce weight and also reserve space for spot welding; spot welding clearance holes are used to reduce weight (the weight reduction effect can reach more than 5%) and provide a process window for subsequent spot welding operations to prevent interference.

[0086] 3. Mounting Component 200 Design – Separate, Standardized, and Commonly Modular, its Composition Structure is as follows: Left / Right Mount Component 220: Includes mounting plate + mounting sleeve; Front mount assembly 230: upper / lower mounting plate + mounting sleeve; The mounting component 200 is separately molded from the frame → each can use a dedicated mold without affecting the others; the mounting plate is made of high-strength steel by stamping, with a wall thickness of 1.0–2.0mm; the mounting plate is a common mold part → improving versatility and reducing the number of molds; the mounting sleeve can be made of steel or aluminum and connected by welding / pressing / adhesion.

[0087] Traditional connection methods are: arc welding connection → easy to burn through and corrode; the connection method of this application is: spot welding connection (penetrating from the inside), a through hole is opened inside the frame, the mounting component 200 extends into the hole and is spot welded to the inner wall of the frame, achieving a firm connection while avoiding external exposure of the weld seam → double improvement of corrosion prevention and sealing.

[0088] 4. Bottom protection plate assembly 600 design – integrated design with localized reinforcement, its structural components are as follows: Bottom guard plate body 610: high-strength steel or hot-formed ultra-high-strength steel, wall thickness 0.8–1.5mm; Mounting reinforcement 620: Matches the mounting holes for a snug fit; High-strength structural adhesive 630: Foamed structural adhesive fills gaps and enhances rigidity; Bottom protective layer 640: Abrasion-resistant coating or additional armor plate; The underbody protection plate is directly connected to the left and right mounting components 220 by bolts, forming an integrated "side mounting-underbody protection plate" structure, which constitutes a Y-axis compression-resistant skeleton. Local reinforcement components can be flexibly arranged according to the overall vehicle safety requirements (such as the high-risk area of ​​bottom impact). This not only improves the lateral compression resistance (meeting the requirements of side pole impact), but also enables reinforcement as needed, avoiding the weight waste caused by global thickening.

[0089] 5. Thermal Management Component 300 Connection – Blind Rivet Replaces FDS Traditional challenges include the difficulty and high cost of drilling FDS (Flow Drill Screw) holes in high-strength steel plates, leading to breakage. The solution proposed in this application involves pre-drilling φ5–6mm blind rivet holes on the lower side of the frame, using blind rivets to fix the water-cooled plate to the bottom of the frame. This method is low-cost, technologically mature, and highly reliable. Compared to FDS, blind rivets do not require a high-temperature plasticizing process, are suitable for thin-walled high-strength steel, and are easy to disassemble.

[0090] The beneficial effects of the technical solution in this application are: 1. The four-section common mold material of the frame significantly reduces the mold opening cost and improves the platform's versatility; 2. The mounting component 200 is molded separately from the frame, supporting modular production and reducing mold complexity; 3. Inner spot welding replaces arc welding, solving problems such as weld burn-through, seal failure, and corrosion; 4. Spot welding avoidance hole design achieves weight reduction (approximately 5–8%) and optimizes the welding process; 5. External encapsulation structure + rivet nut connection improves overall sealing and avoids welding heat damage; 6. The water-cooled plate is connected by a blind rivet, replacing the FDS, reducing costs and improving connection stability; 7. The bottom guard plate is integrated with the side mounting bolts to improve the Y-direction compressive strength and meet safety regulations; 8. Localized structural reinforcement design, with reinforcement as needed, saves materials and reduces weight; 9. The structure is fully bolt-removable, which facilitates later maintenance, replacement, recycling and dismantling.

[0091] Overall benefits: While maintaining the low-cost advantage of steel, it solves the long-standing bottleneck problems of steel lower enclosures, such as "difficult sealing, easy corrosion, weak strength, and cost overrun", and truly achieves the unity of "low-cost materials + high-reliability structure".

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A roll-formed steel lower housing for a power battery, characterized in that, It includes a housing frame (100), mounting assembly (200), thermal management assembly (300), structural sealing assembly (400), connection assembly (500) and bottom guard assembly (600). The box frame (100) includes an inner frame (110) and an outer frame covering structure (120), wherein the inner frame (110) and the outer frame covering structure (120) are connected and integrated by rivet nuts; The mounting component (200) is disposed on the side and / or front end of the box frame (100) and is connected to the inner frame (110) by spot welding. The bottom protective plate assembly (600) is connected to the mounting assembly (200) and the box frame (100) by bolts to form a Y-direction anti-compression reinforced structure; The internal frame (110) is made of four sections of roll-formed profiles with the same cross section welded together. Each section of roll-formed profile is provided with multiple cutting holes for weight reduction and spot welding avoidance.

2. The power battery roll-formed steel lower housing according to claim 1, characterized in that, The internal frame (110) also includes crossbeams, longitudinal beams and reinforcing plates disposed inside the frame, all of which are made of steel and are connected to the roll-formed profile by welding.

3. The power battery roll-formed steel lower housing according to claim 1 or 2, characterized in that, The roll-formed profile has a H-shaped or I-shaped cross section, is made of steel, has a wall thickness of 0.8–1.2 mm, a cross section width of 25–35 mm, and a height of 95–115 mm; The diameter of the cutting holes is 20–25 mm, and the spacing is 70–90 mm.

4. The power battery roll-formed steel lower housing according to claim 1, characterized in that, The mounting component (200) extends into the inner side of the inner frame (110) and is spot-welded through a pre-set through hole on the inner wall of the inner frame (110) to avoid exposed arc weld seams.

5. The power battery roll-formed steel lower housing according to claim 1, characterized in that, The mounting assembly (200) includes a left mounting assembly (210), a right mounting assembly (220), and a front mounting assembly (230). The left mounting assembly (210) includes a left mounting plate and a mounting sleeve. The right mounting assembly (220) includes a right mounting plate and a mounting sleeve. The front mounting assembly (230) includes an upper mounting plate, a lower mounting plate, and a mounting sleeve. The left mounting plate, right mounting plate, upper mounting plate, and lower mounting plate are all high-strength steel stamped parts.

6. The power battery roll-formed steel lower housing according to claim 5, characterized in that, The mounting sleeve is made of steel or aluminum alloy and is fixed to the corresponding mounting plate by welding, pressing or gluing.

7. The power battery roll-formed steel lower housing according to claim 1, characterized in that, The bottom protective plate assembly (600) includes a bottom protective plate body (610), a mounting reinforcement (620), a high-strength structural adhesive (630), and a bottom protective layer (640). The mounting reinforcement (620) is disposed above the bottom protective plate body (610) and the gap is filled with high-strength structural adhesive (630) to enhance the overall rigidity.

8. The power battery roll-formed steel lower housing according to claim 1, characterized in that, The thermal management component (300) is a water-cooled plate, which is connected to the lower side of the internal frame (110) by a pop rivet; The lower side of the internal frame (110) is provided with alternating blind rivet openings and rivet nut openings, the blind rivet openings having a diameter of 5–6 mm and a spacing of 80–90 mm.

9. A method for forming a roll-formed steel lower housing for a power battery as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Roll forming four profiles with the same cross-section, and then cutting them by length, resulting in the first profile, the second profile, the third profile, and the fourth profile; S2. Machining pre-drilled holes for rivet nuts, pre-drilled holes for blind rivets, and spot welding clearance holes on various profiles; S3. The four profiles are laser welded together to form a closed-loop frame to form a frame assembly (111). S4. Weld the crossbeams, longitudinal beams and reinforcing plates to the inside of the frame assembly (111) to form an internal frame (110). S5. The steel plate is cut and bent to serve as the external covering structure (120) of the frame, and connected to the internal frame (110) by rivet nuts to form a box frame (100). S6. Place the mounting component (200) inside the box frame (100) and connect it to the inner frame (110) by spot welding; S7. Connect the thermal management component (300) to the lower side of the housing frame (100) using a blind rivet; S8. Connect the bottom guard plate assembly (600) to the mounting assembly (200), the thermal management assembly (300), and the housing frame (100) respectively using bolts to complete the integration; In step S2, the spot welding clearance hole also has a weight reduction function, with a hole diameter of 20–25 mm and a spacing of 70–90 mm; in step S6, the spot welding operation is located inside the box frame (100) to avoid corrosion and sealing failure caused by external arc welding.

10. A vehicle, characterized in that, Includes the power battery roll-formed steel lower housing as described in any one of claims 1-8, wherein the lower housing is installed at the bottom of the vehicle body as a load-bearing structure for the battery pack, and is used to accommodate and fix the battery cell module.

Images