A lower box of a power battery and a design and manufacturing process thereof

Abstract

The application relates to the technical field of power battery manufacturing, and discloses a power battery lower box body and a design and manufacturing process thereof, which comprise a stainless steel frame, the bottom of the stainless steel frame is sequentially provided with a liquid cooling plate and a bottom guard plate, the stainless steel frame comprises a sleeve edge beam and an electric appliance compartment edge beam, at least three side walls of the stainless steel frame are formed by stretch bending of the sleeve edge beam, and the electric appliance compartment edge beam is connected with the sleeve edge beam to form an outer frame of the stainless steel frame. The sleeve edge beam is manufactured through a pipe rolling process, the cross-section structure is simple, the manufacturing cost is low, the development cycle is short, the power battery lower box body is realized at the boundary corner through the stretch bending technology, welding can be reduced, the deformation problem caused by the welding can be reduced, the overall structure of the power battery lower box body is stable, the one-time qualified rate of the product is high, the manual repair frequency is reduced, the corrosion resistance is good, and the manufacturing cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of power battery manufacturing technology, and more specifically, to a power battery lower casing and its design and manufacturing process. Background Technology

[0002] The lower casing of the power battery is the core structural component of the power battery of new energy vehicles. Currently, among the lower casings of power batteries, ultra-high strength steel battery lower casings, especially ultra-high strength rolled steel battery lower casings, have a lightweight design that is comparable to that of aluminum alloy structure lower casings, which can achieve significant cost reduction. Their safety performance in collisions and fires is also superior to that of existing aluminum alloy battery lower casings.

[0003] Currently, ultra-high strength rolled steel battery lower casings are widely used in mid-to-low-end mass-market vehicles. They can replace aluminum extruded alloy lower casings to achieve cost reduction and efficiency improvement. The multi-cavity rolled structure provides sufficient safety space for the power battery. However, ultra-high strength rolled steel battery lower casings have many electrophoretic blind spots, are prone to corrosion, and pose safety hazards. At the same time, rolled products have complex cross-sections, long cross-section development cycles, and expensive molds, making it difficult to meet customer development needs. In addition, the connection process is complex, with many arc welding processes, resulting in large and difficult-to-control product deformation, leading to low first-pass yield, frequent manual rework, and high tooling and process design costs.

[0004] Therefore, it is necessary to propose a power battery lower casing and its design and manufacturing process to at least partially solve the problems existing in the prior art. Summary of the Invention

[0005] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0006] This invention aims to provide a new process for steel battery lower casing, addressing the current technical pain points of poor corrosion resistance, complex processes, high tooling costs, and long development cycles in steel battery lower casings. This will further enhance the technical advantages of steel battery lower casings and improve the stability and market competitiveness of steel battery lower casing products.

[0007] To at least partially solve the above problems, the present invention provides a lower housing for a power battery, comprising: a stainless steel frame, wherein a liquid cooling plate and a bottom protective plate are sequentially provided at the bottom; The stainless steel frame includes a sleeve side beam and an electrical compartment side beam. The sleeve side beam is bent to form at least three side walls of the stainless steel frame. The electrical compartment side beam is connected to the sleeve side beam to form the outer frame of the stainless steel frame.

[0008] Preferably, the stainless steel frame further includes: a first partition beam disposed within the outer frame, the first partition beam dividing the outer frame into an electrical compartment and a battery cell compartment, one side wall of the electrical compartment being an electrical compartment side beam, and a wire harness support beam being disposed within the electrical compartment; and a second partition beam disposed within the battery cell compartment, the second partition beam dividing the battery cell compartment into multiple battery cell installation spaces.

[0009] Preferably, the outer frame is provided with a mounting beam on the outside, and the mounting beam is provided with a sleeve.

[0010] Preferably, the sleeve side beam includes: an outer pipe fitting and an inner pipe fitting disposed inside the outer pipe fitting, the outer pipe fitting has a rectangular cross-section, the inner pipe fitting has a rectangular or C-shaped cross-section, and the two opposite side walls of the inner pipe fitting are welded to the two side walls of the outer pipe fitting.

[0011] Preferably, structural sealant is provided between the bottom of the stainless steel frame and the liquid cooling plate, sealing cotton is provided near the edge between the liquid cooling plate and the bottom protective plate, and cushioning cotton is provided inside the sealing cotton.

[0012] Preferably, the stainless steel frame is provided with rivet nuts at both the top and bottom for installing a top cover on the top of the stainless steel frame and a liquid cooling plate and a bottom guard plate on the bottom of the stainless steel frame.

[0013] This invention also provides a design and manufacturing process for a power battery lower housing, used to design and manufacture the power battery lower housing described in this invention, comprising: S1. The tubular components used to form the stainless steel frame are made of stainless steel material and prepared by the tube rolling process. The tubular components include sleeve side beams, electrical compartment side beams, first partition beams, second partition beams, and wire harness support beams. S2. The pre-set corner section of the sleeve side beam in step S1 is bent and shaped using a tension bending process. S3. Weld the sleeve side beam bent in step S2 to the electrical compartment side beam to form an outer frame; weld the first partition beam, the second partition beam and the wire harness support beam into the outer frame; S4. The mounting beam made by cold stamping process and the sleeve made by cold heading process are welded together to form the hanging point accessory, and then the hanging point accessory is welded to the outside of the outer frame. S5. Connecting components for mounting the top cover, liquid cooling plate and bottom guard plate are formed at the top and bottom of the stainless steel frame, respectively. S6. Apply structural sealant to the bottom of the stainless steel frame, then install the liquid cooling plate, seals and bottom guard plate, and connect the liquid cooling plate and bottom guard plate to the connecting members at the bottom of the stainless steel frame with fasteners.

[0014] Preferably, the tubular component is a single-layer tube or a multi-layer tube. The single-layer tube has a rectangular cross-section or a C-shaped cross-section, and the multi-layer tube is formed by connecting and welding at least two single-layer tubes with rectangular and / or C-shaped cross-sections together.

[0015] Preferably, the connecting member includes a plurality of mounting holes formed in a stainless steel frame by laser cutting, and rivet nuts installed in the mounting holes.

[0016] Preferably, the minimum effective sealing surface width of the structural sealant is greater than 6 mm.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: The power battery lower housing and its design and manufacturing process described in this invention involve fabricating the sleeve side beam using a tube rolling process, resulting in a simple cross-sectional structure, low manufacturing cost, and short development cycle. The power battery lower housing utilizes a tension bending technique at its boundary corners, which reduces welding and thus minimizes deformation caused by welding. The overall structure of the power battery lower housing is stable, and the product has a high first-pass yield, reducing the frequency of manual rework. It also exhibits good corrosion resistance and lower manufacturing costs.

[0018] The power battery lower housing and its design and manufacturing process described in this invention, as well as other advantages, objectives and features of this invention, will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a partial structural diagram of the lower casing of a power battery in the prior art; Figure 2 This is an exploded structural diagram of the lower housing of the power battery described in this invention; Figure 3 This is a schematic diagram of the stainless steel frame in the lower housing of the power battery according to the present invention; Figure 4 This is a schematic diagram of the cross-sectional structure of the sleeve side beam in the lower housing of the power battery according to the present invention; Figure 5 This is a partial cross-sectional structural diagram of the lower casing of the power battery according to the present invention; Figure 6 This is a flowchart illustrating the design and manufacturing process of the lower housing of the power battery described in this invention. Figure 7 This is a flowchart of step S2 in the design and manufacturing process of the lower housing of the power battery described in this invention. Figure 8 This is a flowchart illustrating step S23 in the design and manufacturing process of the lower housing of the power battery described in this invention.

[0020] In the attached drawings, 1 is the stainless steel frame, 2 is the liquid cooling plate, 3 is the bottom protective plate, 4 is the sleeve side beam, 41 is the outer pipe fitting, 42 is the inner pipe fitting, 5 is the electrical compartment side beam, 6 is the first partition beam, 7 is the wire harness support beam, 8 is the second partition beam, 9 is the mounting beam, 10 is the sleeve, 11 is the structural sealant, 12 is the sealing cotton, 13 is the buffer cotton, 14 is the rivet nut, 16 is the electrical compartment, 17 is the battery cell compartment, 18 is the battery cell installation space, 19 is the roll forming section, 20 is the corner area, 21 is the welding point, and 22 is the inner cavity and overlapping area. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can implement it based on the description.

[0022] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0023] like Figure 1 As shown, in the prior art, the outer frame of the lower housing of the power battery has a complex roll-pressed cross section 19, which has a long development cycle and expensive mold costs. The corner area 20 of the lower housing forms a 90-degree angle splicing, which is complicated in process. In addition, there are many welding points 21 in the lower housing, requiring 10 arc weldings, which can easily cause large product deformation and is difficult to control. The inner cavity and overlapping area 22 are electrophoresis blind spots, and powder spraying is required after electrophoresis, which can easily cause safety hazards.

[0024] like Figure 2 and Figure 3 As shown, the present invention provides a lower housing for a power battery, comprising: a stainless steel frame 1, with a liquid cooling plate 2 and a bottom protective plate 3 arranged sequentially at its bottom; The stainless steel frame 1 includes a sleeve side beam 4 and an electrical compartment side beam 5. The sleeve side beam 4 is bent to form at least three side walls of the stainless steel frame 1. The electrical compartment side beam 5 is connected to the sleeve side beam 4 to form the outer frame of the stainless steel frame 1.

[0025] Both the stainless steel frame 1 and the bottom protective plate 3 can be made of high-strength, low-cost stainless steel. This stainless steel has a yield strength greater than 400 MPa, a tensile strength greater than 800 MPa, and a tensile strength of over 1100 MPa after work hardening. The material has an elongation at break greater than 50% and a PREN (pitting resistance equivalent) value greater than 19. Using this stainless steel material enables the power battery lower casing to achieve the purpose of eliminating electrophoresis and powder coating, reducing manufacturing costs. At the same time, it solves the problem of poor corrosion resistance of steel battery lower casings after electrophoresis and powder coating in the current industry, especially solving the problem that the corrosion resistance at the material fracture location and the overlapping area between parts is lower than that of neutral salt spray 720H. Due to thermal management requirements, the liquid cooling plate 2 is made of aluminum alloy material through cold stamping and brazing. The performance of stainless steel frame 1 meets the relevant national standards for compression and impact resistance; The electrical compartment side beam 5 and the sleeve side beam 4 are connected by MAG welding (gas shielded arc welding) to form the outer frame. The sleeve side beam 4 is first made into a tubular part by the tube rolling process, and then formed into a sleeve side beam 4 by the tube sleeve form, which provides more tube sleeve combination forms for the sleeve side beam 4. Then the sleeve side beam 4 is formed into a U-shape by stretching and bending, which makes its cross section simple, the mold design relatively simple, and the mold opening cycle short. The production efficiency can reach 40 meters / minute. It can replace the traditional steel battery lower box body using roll-pressed steel to form a H-shaped, I-shaped or other irregular complex cross section as the beam structure, solve the problem of insufficient compatibility of roll-pressed steel, and reduce the mold opening cycle and expensive mold costs.

[0026] Through the above design, the sleeve side beam 4 is manufactured by the tube rolling process, which has a simple cross-sectional structure, low manufacturing cost, and short development cycle. The lower box of the power battery uses the stretch bending technology at its boundary corner, which can reduce welding and thus reduce the deformation problem caused by welding. The overall structure of the lower box of the power battery is stable, and the first-pass yield of the product is high, reducing the frequency of manual rework, with good corrosion resistance and reduced manufacturing cost.

[0027] like Figure 3 As shown, in one embodiment, the stainless steel frame 1 further includes: a first partition beam 6 disposed within the outer frame, the first partition beam 6 dividing the outer frame into an electrical compartment 16 and a battery cell compartment 17, one side wall of the electrical compartment 16 being an electrical compartment side beam 5, and a wire harness support beam 7 disposed within the electrical compartment 16; and a second partition beam 8 disposed within the battery cell compartment 17, the second partition beam 8 dividing the battery cell compartment 17 into multiple battery cell installation spaces 18.

[0028] The first partition beam 6, the second partition beam 8, and the wire harness support beam 7 are all tubular components formed by a tubing rolling process, with rectangular or C-shaped cross-sections. The first partition beam 6 is connected to the two side walls of the sleeve side beam 4 by MAG welding. The second partition beam 8 can be designed and planned according to the required number of battery cell installation spaces 18, forming multiple battery cell installation spaces 18 by MAG welding. The wire harness support beam 7 is connected between the first partition beam 6 and the electrical compartment side beam 5 by MAG welding, and the number of wire harness support beams 7 is also set according to needs. The first partition beam 6, the second partition beam 8, and the wire harness support beam 7 form multiple spaces inside the outer frame, facilitating the installation and connection of battery cells and electrical components. One or more brackets or holes are allowed inside the outer frame for the installation of auxiliary parts such as wire harnesses, copper busbars, and busbars.

[0029] like Figure 3 and Figure 5 As shown, in one embodiment, a mounting beam 9 is provided on the outer side of the outer frame, and a sleeve 10 is provided on the mounting beam 9.

[0030] The mounting beam 9 is manufactured using a cold stamping process, and the sleeve 10 is manufactured using a cold heading process. The sleeve 10 is fitted onto the mounting beam 9, and the two are connected by laser-guided self-fusion welding to form a sub-assembly (sub-assembly accessory, i.e., mounting point accessory). Then, the mounting point accessory is connected to the outer side of the outer frame using MAG welding to form the outer frame. Figure 5 The circles in the diagram represent welding points, and the outer frame allows for the placement of one or more mounting points for auxiliary body parts.

[0031] like Figure 4 As shown, in one embodiment, the sleeve side beam 4 includes: an outer pipe 41 and an inner pipe 42 disposed inside the outer pipe 41. The cross-section of the outer pipe 41 is rectangular, and the cross-section of the inner pipe 42 is rectangular or C-shaped. The two opposite side walls of the inner pipe 42 are welded to the two side walls of the outer pipe 41.

[0032] The inner fitting 42 and the outer fitting 41 are welded using laser penetration self-fusion welding and metallurgical fusion nugget controlled spot welding processes, such as... Figure 4 The circles in the diagram represent welding points or weld beads, thus forming the sleeve side beam 4. The inner pipe fitting 42 and the outer pipe fitting 41 can be formed by pipe rolling process, and then assembled and fixed by welding.

[0033] like Figure 2 and Figure 5 As shown, in one embodiment, a structural sealant 11 is provided between the bottom of the stainless steel frame 1 and the liquid cooling plate 2, a sealing cotton 12 is provided near the edge between the liquid cooling plate 2 and the bottom protective plate 3, and a buffer cotton 13 is provided inside the sealing cotton 12.

[0034] Before installing the liquid cooling plate 2, apply structural sealant 11 to the bottom of the stainless steel frame 1 to ensure that the airtightness of the liquid cooling plate 2 after installation meets the IP67 standard (protection safety level) requirements. Before installing the bottom protective plate 3, several buffer cotton 13s are arranged between the liquid cooling plate 2 and the bottom protective plate 3. Then, a sealing cotton 12 is arranged around the outside of the buffer cotton 13s to ensure that the airtightness of the bottom protective plate 3 after installation meets the IP67 standard (protection safety level) requirements. The internal buffer cotton 13 provides noise reduction and energy absorption functions for the lower box of the power battery, and meets the impact performance of the bottom.

[0035] like Figure 5 As shown, in one embodiment, the stainless steel frame 1 is provided with rivet nuts 14 at both the top and bottom for installing a top cover on the top of the stainless steel frame 1 and a liquid cooling plate 2 and a bottom protective plate 3 on the bottom of the stainless steel frame 1.

[0036] Place the top cover on top of the stainless steel frame 1, and then tighten it with screws and rivet nuts 14 to connect and fix the top cover to the stainless steel frame 1; place the liquid cooling plate 2 and the bottom protective plate 3 at the bottom of the stainless steel frame 1 in sequence, and then tighten them with screws and rivet nuts 14 below to connect and fix the liquid cooling plate 2 and the bottom protective plate 3 to the stainless steel frame 1.

[0037] like Figure 6 As shown, the present invention also provides a design and manufacturing process for the lower housing of a power battery, including: S1. The tubular components used to form the stainless steel frame 1 are made of stainless steel material and prepared by the tube rolling process. The tubular components include the sleeve side beam 4, the electrical compartment side beam 5, the first partition beam 6, the second partition beam 8, and the wire harness support beam 7. S2. The pre-set corner section of the sleeve side beam 4 in step S1 is bent and shaped using a stretch bending process. The bending limit R angle is selected and determined based on the thickness of the sleeve side beam 4; S3. Weld the sleeve side beam 4, which was bent in step S2, to the electrical compartment side beam 5 to form an outer frame; weld the first partition beam 6, the second partition beam 8, and the wire harness support beam 7 into the outer frame; S4. The mounting beam 9, which is made by cold stamping, and the sleeve 10, which is made by cold heading, are welded together to form a hanging point accessory, and then the hanging point accessory is welded to the outside of the outer frame. S5. Connecting components for mounting the top cover, liquid cooling plate 2 and bottom protective plate 3 are formed at the top and bottom of the stainless steel frame 1, respectively. S6. Apply structural sealant 11 to the bottom of the stainless steel frame 1, then install the liquid cooling plate 2, sealant and bottom guard plate 3, and connect the liquid cooling plate 2 and bottom guard plate 3 to the connecting members at the bottom of the stainless steel frame 1 with fasteners.

[0038] The sealing components are sealing cotton 12 and buffer cotton 13. Sealing cotton 12 is provided near the edge between the liquid cooling plate 2 and the bottom protective plate 3, and buffer cotton 13 is provided inside the sealing cotton 12.

[0039] The sleeve side beam 4, the electrical compartment side beam 5, the first partition beam 6, the second partition beam 8, the wire harness support beam 7, and the bottom protective plate 3 can all be made of high-strength, low-cost stainless steel. The yield strength of this stainless steel is greater than 400 MPa, the tensile strength is greater than 800 MPa, and the tensile strength reaches more than 1100 MPa after work hardening. The material's elongation at break is greater than 50%, and the PREN (pitting corrosion equivalent) value is greater than 19. The sleeve side beam 4 is first made into a tubular part by a tube rolling process, and then formed into a sleeve side beam 4 by a tube-to-tube method; then the sleeve side beam 4 is formed into a U-shape by stretching and bending, which makes its cross-section simple, the mold design relatively simple, and the mold opening cycle short; the electrical compartment side beam 5 and the sleeve side beam 4 are connected by MAG welding (metal galvanized gas shielded arc welding) to form an outer frame, and the first partition beam 6, the second partition beam 8, and the wire harness support beam 7 are connected to the outer frame by MAG welding; the sleeve 10 is fitted onto the hanging beam 9, and the two are connected by laser penetration self-fusion welding to form a hanging point accessory, and then the hanging point accessory is connected to the outside of the outer frame by MAG welding; the upper cover, liquid cooling plate 2 and bottom protective plate 3 can be connected to the stainless steel frame 1 by the connecting components on the stainless steel frame 1.

[0040] The above process can reduce the manufacturing cost of the lower battery box, reduce welding, thereby reducing deformation caused by welding, making the overall structure of the lower battery box more stable, improving the product qualification rate, and achieving short cycle, low cost, corrosion resistance greater than 1000h, less welding and less deformation.

[0041] In one embodiment, the sleeve side beam 4 is prepared by a tube rolling process, including: The inner tube 42 and the outer tube 41 are manufactured by the tube rolling process, and the outer tube 41 is sleeved on the outside of the inner tube 42. Using laser penetration self-fusion welding, a continuous weld is applied along the length of the two opposite inner walls of the outer pipe fitting 41, and the weld simultaneously melts through the pipe walls of the outer pipe fitting 41 and the inner pipe fitting 42. Before, during, or after laser penetration self-fusion welding, multiple discrete spot weld nuggets are formed between the outer fitting 41 and the inner fitting 42 along the length direction of the sleeve side beam 4.

[0042] In the laser penetration welding process, the welding is carried out by oscillating the laser beam, and the oscillation trajectory of the laser beam is circular or "∞" shaped. During the metallurgical molten core controlled spot welding process, the molten cores are not uniformly distributed along the length of the sleeve side beam 4. The distribution density of the molten cores is higher in the preset corner section than in the straight section.

[0043] like Figure 7 As shown, in one embodiment, in step S2, the preset corner section of the sleeve side beam 4 in step S1 is bent and shaped using a stretch bending process, including: S21. Based on the three-dimensional geometric data, material property data, and characteristic parameters of the welded connection area of ​​the sleeve side beam 4, a finite element simulation model including the welded joint model is established. S22. Based on the finite element simulation model, with the goal of minimizing cross-sectional distortion and controlling the thinning rate, and with the constraints of wrinkle prevention and weld joint safety, the key parameters of the tension bending process are optimized through iterative simulation; wherein, the key parameters include at least the pre-tension force. S23. Based on the finite element simulation model, the bending process under the initial mold surface is simulated to obtain the deviation between the predicted shape and the target shape of the sleeve side beam 4 after unloading. Based on the deviation, the target mold surface after compensation is obtained through reverse mapping and iterative simulation. S24. Integrate and optimize the key parameters and compensated target mold surface data to form a bending process design document to guide production.

[0044] The characteristic parameters of the welded joint area in step S21 include: The parameters of the continuous weld are based on the anisotropic elastoplastic material properties calibrated by actual metallographic and mechanical properties. The parameters of the spot weld nugget at discrete points are modeled using a cohesive force model or a spring element, and its failure criteria are set.

[0045] Spring elements are a special type of functional element in Abaqus, primarily used to simulate elastic connections or constraints in structures.

[0046] In step S22, the key parameters of the bending process are optimized through iterative simulation. This includes taking the prevention of wrinkling on the inner side of the bend and the prevention of overload of the welded joint as constraints, and controlling the maximum thinning rate on the outer side of the bend below a set threshold as the optimization objective. The simulation software automatically adjusts the input value of the pre-tension force and performs multiple simulation calculations until the optimal pre-tension force value or optimal range that simultaneously satisfies the constraints and the optimization objective is found.

[0047] Step S22 further includes the process of determining the minimum safe bending radius at the preset corner section: Based on the material elongation data of the input sleeve side beam 4 and the strain path of the element nodes in the finite element simulation model, the risk of material cracking is predicted, and the recommended value of the minimum safe bending radius required for the sleeve side beam 4 at different bending positions is dynamically output.

[0048] like Figure 8 As shown, in step S23, the compensated target mold surface is obtained based on the deviation through reverse mapping and iterative simulation, including: S231. Obtain the displacement deviation field of the sleeve side beam 4 after the first simulation; S232. The displacement deviation field is superimposed onto the initial mold surface node in reverse to generate the first compensation surface; S233. Based on the first compensation surface, the sleeve side beam 4 is simulated again to obtain the deviation between the new predicted shape and the target shape. S234. Repeat steps S231-S233 to perform multiple compensations and simulation iterations of the profile until the deviation between the predicted shape and the target shape of the sleeve side beam 4 falls within the preset tolerance range. The profile used at this time is the compensated target mold profile.

[0049] The displacement deviation field can be understood as a vectorized dataset of spatial positional differences between the surface (or solid mesh node) of the predicted three-dimensional digital model obtained after the first simulation of the sleeve side beam 4 in the finite element simulation environment and the corresponding position of the target three-dimensional digital model, which serves as the design benchmark. The predicted three-dimensional digital model corresponds to the predicted shape of the sleeve side beam 4, and the target three-dimensional digital model corresponds to the target shape of the sleeve side beam 4.

[0050] The above method can simulate the bending process of the sleeve side beam 4, so that the actual bent sleeve side beam 4 is as close as possible to the design target, ensuring the product qualification rate. Furthermore, simulation can shorten the development cycle and reduce costs. By accurately calculating the optimal pre-tension force, predicting the minimum safe bending radius and thinning rate through simulation, the risks of excessive stretching, wrinkling, cracking or weld damage in the actual bending process can be avoided or reduced, achieving a balance between lightweight and structural reliability.

[0051] In one embodiment, the tubular component is a single-layer tube or a multi-layer tube. The single-layer tube has a rectangular cross-section or a C-shaped cross-section, and the multi-layer tube is formed by connecting and welding at least two single-layer tubes with rectangular and / or C-shaped cross-sections together.

[0052] The tubular component is formed by a tube rolling process. Its mold design is simple. The multi-layer tube design is in the form of a tube-in-tube, which can provide more combination possibilities for the tube side beam 4 and make it easier to achieve the design purpose. This technical solution can replace the beam structure of the traditional steel battery lower box and has good structural stability.

[0053] In one embodiment, the connecting member includes a plurality of mounting holes formed in a stainless steel frame 1 by laser cutting, and rivet nuts 14 installed in the mounting holes.

[0054] Multiple mounting holes are formed at the top and bottom of the stainless steel frame 1 by laser cutting, and then rivet nuts 14 are fixed in the mounting holes. The mounting holes formed by laser cutting are precise in position and size, which facilitates the installation of rivet nuts 14 and makes it easier to install and fix the top cover, liquid cooling plate 2 and bottom protective plate 3.

[0055] In one embodiment, the minimum effective sealing surface width of the structural sealant 11 is greater than 6 mm.

[0056] The width of the structural sealant 11 is designed to ensure the airtightness of the liquid cooling plate 2 after installation, thereby ensuring the sealing effect of the lower housing of the power battery.

[0057] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0058] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0059] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the present invention, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A lower housing for a power battery, characterized in that, include: A stainless steel frame (1) is provided with a liquid cooling plate (2) and a bottom protective plate (3) in sequence at its bottom. The stainless steel frame (1) includes a sleeve side beam (4) and an electrical compartment side beam (5). The sleeve side beam (4) is formed by bending to form at least three side walls of the stainless steel frame (1). The electrical compartment side beam (5) is connected to the sleeve side beam (4) to form the outer frame of the stainless steel frame (1). The sleeve side beam (4) includes: an outer pipe fitting (41) and an inner pipe fitting (42) disposed inside the outer pipe fitting (41). The cross section of the outer pipe fitting (41) is rectangular, and the cross section of the inner pipe fitting (42) is rectangular or C-shaped. The two opposite side walls of the inner pipe fitting (42) are welded to the two side walls of the outer pipe fitting (41). The sleeve side beam (4) is first made into a tubular part by a tube rolling process, and then formed into a sleeve side beam (4) in the form of a tube sleeve. Then the sleeve side beam (4) is formed into a U-shape by stretching and bending. The process of preparing the sleeve side beam (4) by tube rolling includes: The inner tube (42) and the outer tube (41) are manufactured by the tube rolling process, and the outer tube (41) is fitted onto the outside of the inner tube (42); Using laser penetration self-fusion welding, a continuous weld is applied along the length of the two opposing inner walls of the outer pipe fitting (41), and the weld simultaneously melts through the pipe walls of the outer pipe fitting (41) and the inner pipe fitting (42). Along the length direction of the sleeve side beam (4), multiple discrete spot weld nuggets are formed between the outer pipe fitting (41) and the inner pipe fitting (42); the spot weld nuggets are not uniformly distributed along the length direction of the sleeve side beam (4), and the distribution density of spot weld nuggets in the preset corner section is higher than that in the straight section.

2. The lower housing of the power battery according to claim 1, characterized in that, The stainless steel frame (1) further includes: a first partition beam (6) disposed within the outer frame, the first partition beam (6) dividing the outer frame into an electrical compartment (16) and a battery cell compartment (17), one side wall of the electrical compartment (16) being an electrical compartment side beam (5), and a wire harness support beam (7) disposed within the electrical compartment (16); and a second partition beam (8) disposed within the battery cell compartment (17), the second partition beam (8) dividing the battery cell compartment (17) into multiple battery cell installation spaces (18).

3. The lower housing of the power battery according to claim 2, characterized in that, The outer frame is provided with a mounting beam (9), and the mounting beam (9) is provided with a sleeve (10).

4. The lower housing of the power battery according to claim 1, characterized in that, Structural sealant (11) is provided between the bottom of the stainless steel frame (1) and the liquid cooling plate (2), and sealing cotton (12) is provided near the edge between the liquid cooling plate (2) and the bottom guard plate (3), and buffer cotton (13) is provided inside the sealing cotton (12).

5. The lower housing of the power battery according to claim 1, characterized in that, The stainless steel frame (1) is provided with rivet nuts (14) at the top and bottom for installing a top cover on the top of the stainless steel frame (1) and a liquid cooling plate (2) and a bottom guard plate (3) on the bottom of the stainless steel frame (1).

6. A design and manufacturing process for a power battery lower casing, used for designing and manufacturing the power battery lower casing as described in any one of claims 1-5, characterized in that, include: S1. Using stainless steel material, tubular components for forming the stainless steel frame (1) are prepared by tubing process. The tubular components include sleeve side beam (4), electrical compartment side beam (5), first partition beam (6), second partition beam (8) and wire harness support beam (7). S2. The pre-set corner section of the sleeve side beam (4) in step S1 is bent and shaped using a stretch bending process. S3. Weld the sleeve side beam (4) after bending in step S2 to the electrical compartment side beam (5) to form an outer frame; weld the first partition beam (6), the second partition beam (8) and the wire harness support beam (7) inside the outer frame; S4. The hanging beam (9) made by cold stamping process and the sleeve (10) made by cold heading process are connected by welding to form a hanging point accessory, and then the hanging point accessory is welded to the outside of the outer frame. S5. Connecting components for mounting the top cover, liquid cooling plate (2) and bottom guard plate (3) are formed at the top and bottom of the stainless steel frame (1), respectively. S6. Apply structural sealant (11) to the bottom of the stainless steel frame (1), then install the liquid cooling plate (2), seals and bottom guard plate (3), and connect the liquid cooling plate (2) and bottom guard plate (3) to the connecting members at the bottom of the stainless steel frame (1) by fasteners.

7. The design and manufacturing process of the lower housing of the power battery according to claim 6, characterized in that, The tubular component is a single-layer tube or a multi-layer tube. The single-layer tube has a rectangular cross-section or a C-shaped cross-section, and the multi-layer tube is formed by connecting and welding at least two single-layer tubes with rectangular and / or C-shaped cross-sections together.

8. The design and manufacturing process of the lower housing of the power battery according to claim 6, characterized in that, The connecting member includes a plurality of mounting holes formed in a stainless steel frame (1) by laser cutting, and rivet nuts (14) installed in the mounting holes.

9. The design and manufacturing process of the lower housing of the power battery according to claim 6, characterized in that, The minimum effective sealing surface width of the structural sealant (11) is greater than 6 mm.

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