A method for stamping a top cover sheet

Abstract

The application provides a top cover sheet stamping forming method, adopts a top cover sheet raw material with a thickness of 2.5mm to 3mm, and sequentially executes the following steps: firstly, the raw material is punched into a screen mesh hole; then, a back surface recess corresponding to a front surface protrusion is formed by stamping, the screen mesh hole is arranged in the front surface protrusion area; then, a middle sunken step is formed in the middle part of the front surface protrusion by stamping, the lower surface of the middle sunken step is used as a cell support surface; finally, the transition position of the step is rounded and shaped, a ring-shaped explosion-proof valve installation sunken step is formed, and a ring-shaped explosion-proof valve support platform with a thickness of 2.5mm to 3mm is formed between the two steps. The stamping process sequence is optimized, the thickened plate and the reasonable fillet structure are matched, the risk of stretching and thinning and cracking of the step side wall is reduced, and the forming yield and structural strength of the integrated screen mesh top cover sheet are improved.

Description

Technical Field

[0001] This invention relates to the field of energy storage batteries, and more specifically to a method for stamping a top cover sheet. Background Technology

[0002] Under thermal runaway conditions, the vaporization of the electrolyte and the decomposition of active materials inside the cell of a large-capacity lithium battery will instantly generate a large amount of high-temperature and high-pressure gas, causing a sudden increase in the internal pressure of the battery. After being subjected to high temperature and gas expansion and compression, the internal electrode plates, separators and other components are prone to deformation, blocking the pressure relief channel of the explosion-proof valve located on the top cover, causing the explosion-proof valve to fail to open and relieve pressure normally, which in turn leads to safety accidents such as battery bulging, explosion, and fire.

[0003] To avoid the aforementioned defects, existing energy storage battery cover assemblies generally adopt a screen support structure: the top cover plate body is first stamped and formed separately, and then an independent screen and support bracket are prepared. Subsequently, the screen and bracket are fixed to the inside of the explosion-proof valve of the top cover plate through processes such as laser welding and resistance welding. The screen and bracket form a support, which supports the electrode assembly in the event of thermal runaway of the battery cell or deformation of the electrode assembly, and reserves a gas flow gap to ensure that the pressure relief passage of the explosion-proof valve is unobstructed, thus structurally preventing the electrode plate from blocking the explosion-proof valve.

[0004] However, the separate assembly solution has inherent drawbacks: the screen and support need to be manufactured separately by stamping, and an additional welding assembly process is required. This results in a large number of parts, a lengthy process, and high costs for raw materials and welding labor. Furthermore, the multiple processes reduce the overall production efficiency of the battery top cover, hindering the large-scale, cost-effective production of energy storage batteries. Therefore, the industry has developed a technology that integrates the top cover sheet with the stamped screen and support ribs, eliminating the need for separate parts and welding processes.

[0005] like Figure 1 As shown, the stamping process for the existing integrated explosion-proof screen top cover is as follows: 1) The screen mesh is formed by punching in a pre-set area of ​​the top cover blank using a punching process; 2) Extrude a 0.5mm high outer ring step with the front side facing upward, and simultaneously extrude the corresponding position on the back side upward to form a back step; 3) The explosion-proof valve steps are formed by downward stamping and are arranged around the center; 4) The middle step at the center of the final stamping forming.

[0006] like Figure 2 As shown, the side of the explosion-proof valve is the welding positioning sharp corner of the explosion-proof valve. This position is a compound corner where multiple bent steps intersect. Because the existing process is to first stamp to form the explosion-proof valve steps, and then stamp to form the intermediate steps, when the intermediate steps are stamped, the sharp corner collapses into an arc surface after the stamping pressure is released and springs back, which cannot form a flat vertical edge and does not meet the dimensional requirements of the subsequent laser welding and assembly of the explosion-proof valve.

[0007] like Figure 3 As shown, the wall thickness of the intermediate step obtained through the existing process is only about 1.3mm. The forming allowance of the plate is limited. When the intermediate step is punched downward, the side wall of the step can only be fed by the outer plate base material in one direction. The thinning rate of the thin wall position exceeds the limit, and the wall thickness of the step is very easy to be suddenly reduced and tear. In addition, the screen mesh is pre-cut, and the complete plate is divided by the mesh. The stress concentration gaps formed at the edges of the mesh make it easier for the intermediate step to break and be scrapped at the connection with the surrounding base.

[0008] Therefore, how to overcome the shortcomings of the existing technology is the subject of this invention. Summary of the Invention

[0009] The purpose of this invention is to provide a method for stamping a top cover sheet to solve the above-mentioned technical problems.

[0010] To achieve the above objectives, the present invention provides a top cover sheet stamping forming method, comprising the following steps: Step 1: Punch and cut the top cover sheet material with a thickness of 2.5mm to 3mm to form the screen mesh; Step 2: Stamp the top cover sheet material to form a front convex shape. The screen mesh is arranged in the forming area of ​​the front convex shape. At the same time as stamping the front convex shape, the back of the top cover sheet is correspondingly recessed. Step 3: Stamp a middle recessed step with a depth of 5mm to 5.4mm in the central area of ​​the front protrusion. The middle recessed step includes a middle recessed step platform and an initial middle recessed step sidewall. The lower end of the initial middle recessed step sidewall has an inward concave fillet radius of 0.8mm to 1.2mm and an outward convex fillet radius of 2.8mm to 3.2mm. The thickness of the step surface of the middle recessed step is 2.5mm to 3mm. Step 4: Stamp the initial intermediate sinking step sidewall and its outer edge to form the surrounding explosion-proof valve installation sinking step sidewall and the final intermediate sinking step sidewall, and form an annular explosion-proof valve support platform with a thickness of 2.5mm to 3mm between the intermediate sinking step sidewall and the explosion-proof valve installation sinking step sidewall.

[0011] In a further technical solution, in step 4, the explosion-proof valve welding step is simultaneously stamped and formed. The explosion-proof valve welding step is arranged around the outside of the side wall of the explosion-proof valve installation sinking step, and the explosion-proof valve welding step forms a raised welding angle. An installation area for assembling a protective film is formed between the explosion-proof valve welding step and the front protrusion.

[0012] In a further technical solution, the screen mesh formed in step 1 includes a central mesh and an outer mesh, the outer edge of the central sinking step surrounds the central mesh, and the central mesh extends at least partially to the side wall of the central sinking step.

[0013] In a further technical solution, the outer edge of the explosion-proof valve installation sinking step formed in step 4 surrounds the outer mesh, and the outer mesh is at least partially located on the side wall of the explosion-proof valve installation sinking step.

[0014] In a further technical solution, in step 4, the connection between the annular explosion-proof valve support platform and the side wall of the middle sinking step is stamped with the following dimensions: inner convex fillet radius of 2.3mm to 2.7mm and outer concave fillet radius of 0.4mm to 0.6mm.

[0015] In a further technical solution, in step 4, the side wall of the sinking step for installing the explosion-proof valve is stamped with the following dimensions: inner concave fillet radius of 0.8mm to 1.2mm, inner convex fillet radius of 1.8mm to 2.2mm, outer convex fillet radius of 2.8mm to 3.2mm, and outer concave fillet radius of 0.4mm to 0.6mm.

[0016] In a further technical solution, in step 4, a cell support is simultaneously formed by stamping at both ends of the top cover sheet material, and the cell support has the same protrusion direction as the middle sinking step.

[0017] In a further technical solution, in step 4, the stamped battery cell bracket includes a pre-deformed step formed simultaneously and a bracket step connected to the inner side of the pre-deformed step.

[0018] In a further technical solution, the depth of the pre-deformed step is 0.6 mm to 0.8 mm.

[0019] In a further technical solution, the inner sidewall convex fillet radius of the support step is 3.3mm to 3.7mm, the outer sidewall concave fillet radius is 0.8mm to 1.2mm, and the outer sidewall convex fillet radius is 1.0mm to 1.4mm.

[0020] The top cover sheet stamping method provided in this application has the following technical advantages compared with the prior art: This invention uses 2.5mm to 3mm thickened raw material plates and employs a step-by-step forming method: first punching the screen mesh holes, forming the front raised steps, and then stamping the middle recessed steps and the explosion-proof valve installation recessed steps. This changes the traditional process sequence of forming the explosion-proof valve steps first and then the middle steps. By prioritizing the forming of the middle recessed steps, the middle recessed steps are fully formed and their wall thickness is maintained at 2.5mm to 3mm. This effectively avoids the problem of excessive stretching of the middle step sidewalls during subsequent forming processes, which could lead to thinning and breakage. This significantly improves the overall structural strength and forming stability of the integrated screen support structure.

[0021] Meanwhile, this invention forms a stable annular explosion-proof valve support platform between the intermediate recessed step and the explosion-proof valve installation recessed step, overcoming the defects of insufficient wall thickness and severe stress concentration at the transition position of the steps in traditional processes. Under the premise of pre-opening screen mesh holes and weakening the continuity of the sheet metal, the structural cooperation of the thickened sheet metal and thick-walled support platform effectively improves the material tension and local thinning phenomenon during the stamping process, avoids cracking at the connection of the explosion-proof valve steps, and ensures the forming integrity and structural support reliability of the integrated screen mesh of the top cover and the explosion-proof valve installation structure. Attached Figure Description

[0022] Figure 1 A schematic diagram of the existing top cover plate stamping process; Figure 2 The problem of corner collapse at the welded corner of the explosion-proof valve caused by the stamping of the existing top cover plate; Figure 3 The problem of sidewall cracking in the middle sinking step caused by the stamping of the existing top cover plate; Figure 4 This is a schematic diagram of the structure of step 2 in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of step 3 in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of step 4 in an embodiment of the present invention; Figure 7 This is a top view of step 2 in an embodiment of the present invention; Figure 8 This is a cross-sectional view of step 2 in an embodiment of the present invention; Figure 9 This is a top view of step 3 in an embodiment of the present invention; Figure 10 This is a cross-sectional view of step 3 in an embodiment of the present invention; Figure 11 for Figure 10 A magnified view of a section at point A in the middle; Figure 12 This is a top view of step 4 in an embodiment of the present invention; Figure 13 for Figure 12EE section sectional view; Figure 14 for Figure 13 A magnified view of a section at point B in the middle; Figure 15 for Figure 12 FF section sectional view; Figure 16 for Figure 15 Enlarged view of section C in the image; Figure 17 This is a three-dimensional structural diagram after step 4 of the present invention is completed; Figure 18 for Figure 17 The corresponding top view; Figure 19 for Figure 17 Sectional view of the GG section; Figure 20 for Figure 19 Enlarged view of part D in the image; In the attached diagrams: 1-Top cover material; 11-Screen; 2-Screen mesh; 21-Middle mesh; 22-Outer mesh; 3-Front protrusion; 4-Back depression; 5-Middle recessed step; 51-Middle recessed step platform; 52-Initial middle recessed step sidewall; 52'-Middle recessed step sidewall; 521-Middle outward convex rounded corner; 522-Middle inward concave rounded corner; 523-Middle outward concave rounded corner; 524-Middle inward convex rounded corner; 6-Explosion-proof valve installation recessed step; 61-Annular explosion-proof valve installation recessed step; Explosion-proof valve support platform; 62-Explosion-proof valve installation recessed step sidewall; 621-Explosion-proof convex fillet; 622-Explosion-proof concave fillet; 623-Explosion-proof convex fillet; 8-Explosion-proof valve welding step; 81-Explosion-proof valve welding corner; 9-Bracket; 91-Pre-deformed step; 92-Bracket step; 921-Bracket step platform; 922-Bracket step sidewall; 9221-Bracket concave fillet; 9222-Bracket concave fillet; 9223-Bracket concave fillet; 9224-Bracket concave fillet. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] The terms "first," "second," etc., used in this article do not specifically refer to order or sequence, nor are they intended to limit this case; they are merely used to distinguish components or operations described using the same technical terms.

[0025] The terms "connection" or "positioning" as used in this article can refer to two or more components or devices making direct physical contact with each other, or making indirect physical contact with each other, or to two or more components or devices operating or moving with each other.

[0026] The terms “include,” “including,” and “have” used in this article are all open-ended, meaning they include but are not limited to.

[0027] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the case.

[0028] The terms “front,” “back,” “up,” “down,” “left,” and “right” used in this article are directional terms. In this case, they are only used to describe the positional relationship between the structures and are not intended to limit the specific direction of the protection scheme or its actual implementation.

[0029] This embodiment discloses a method for stamping a top cover sheet. The method uses a top cover sheet raw material 1 with a thickness of 2.5mm to 3mm for integral stamping. Thicker sheet material can improve the tensile strength and crack resistance of the structure. This method, combined with a specific stamping process sequence and multiple rounded corner structural designs, can improve the problems of sidewall breakage, insufficient support wall thickness, and weak overall structural strength in the traditional one-piece screen top cover sheet forming process.

[0030] The specific molding steps of this invention are as follows: Step 1: Perform integral punching and cutting on the top cover sheet raw material 1. Form the screen 11 and screen mesh 2 structure in the pre-set area of ​​the blank. The screen mesh 2 includes a central mesh 21 and an outer mesh 22, completing the hollow structure processing of the sheet material in advance.

[0031] Step 2, refer to Figure 4 , Figure 7 The top cover sheet material 1 is stamped to form a front protrusion 3 with a height of 0.5mm. Simultaneously, a back recess 4 is formed on the back of the top cover sheet, as detailed in the reference [reference needed]. Figure 8 All screen mesh openings 2 are arranged within the forming area of ​​the front protrusion 3, ensuring that the structure and position of the screen 11 are uniform and regular.

[0032] Step 3, refer to Figure 5 , Figure 9 In the central area of ​​the front protrusion 3, a central recessed step 5 is preferentially stamped, including a central recessed step platform 51 and an initial central recessed step sidewall 52, as detailed in the reference. Figure 10The thickness of the central recessed step platform 51 is 2.5mm to 3mm, and the recessed depth is 5mm to 5.4mm compared to the upper surface of the front protrusion 3. The lower surface of the central recessed step platform 51 is the cell support surface, which can stably support the cell structure.

[0033] Combination Figure 11 A magnified view of section A shows that the stamping process creates a concave fillet 522 and a convex fillet 521 at the lower end of the initial intermediate recessed step sidewall 52. The radius of the concave fillet 522 is 0.8 mm to 1.2 mm, and the radius of the convex fillet 521 is 2.8 mm to 3.2 mm. This fillet radius design allows for more gradual deformation of the sidewall and reduces stress concentration.

[0034] Traditional one-piece screen cover molding processes have inherent defects. The screen mesh openings need to be punched first, disrupting the overall continuity of the sheet material. During subsequent step stamping, the sidewalls of the steps are prone to stretching and thinning. Therefore, the industry standard is to use a stamping sequence from the outside in, first forming the outer explosion-proof valve installation recessed step 6, then forming the middle recessed step 5. However, if the outer explosion-proof valve installation recessed step 6 is formed first, the material will be stretched again during the subsequent stamping of the middle recessed step 5, easily resulting in a thinner wall thickness for the middle recessed step and insufficient support performance.

[0035] Step 4, refer to Figure 6 , Figure 12 This embodiment optimizes the stamping process sequence. After the intermediate recessed step 5 is fully formed, the initial intermediate recessed step sidewall 52 and the transition position between the intermediate recessed step 5 and the front protrusion 3 are stamped. This forms the surrounding recessed step 6 for the explosion-proof valve installation, the cross-sectional structure of which can be referenced. Figure 13 .

[0036] The explosion-proof valve installation recessed step 6 includes an annular explosion-proof valve support platform 61 and an explosion-proof valve installation recessed step sidewall 62. The explosion-proof valve support platform 61 is recessed by approximately 3.2 mm relative to the upper surface of the front protrusion 3. The initial intermediate recessed step sidewall 52 is bent and shortened to form the final intermediate recessed step sidewall 52', while an annular explosion-proof valve support platform 61 with a thickness of 2.5 mm to 3 mm is formed between the intermediate recessed step sidewall 52' and the explosion-proof valve installation recessed step sidewall 62.

[0037] This process sequence allows the intermediate recessed step 5 to be pre-formed, reducing the risk of thinning and breakage of the initial intermediate recessed step sidewall 52 due to secondary stretching. Simultaneously, the stamping range of the intermediate recessed step 5 only covers the central mesh area 21. The forming process does not occupy or stretch the material of the outer explosion-proof valve forming area, effectively ensuring the forming thickness and support performance of the annular explosion-proof valve support platform 61 and the explosion-proof valve installation recessed step sidewall 62, thus improving the shortcomings of traditional forming processes.

[0038] Combination Figure 15 , Figure 16 The enlarged structure at point C allows for simultaneous rounding of multiple corners during the installation of the recessed step 6 of the explosion-proof valve. The connection point between the annular explosion-proof valve support platform 61 and the side wall 52' of the intermediate recessed step is equipped with a central convex rounded corner 524 and a central concave rounded corner 523. The radius of the central convex rounded corner 524 is 2.3mm to 2.7mm, and the radius of the central concave rounded corner 523 is 0.4mm to 0.6mm.

[0039] The side wall 62 of the recessed step for the explosion-proof valve installation is equipped with explosion-proof concave rounded corners 622, convex rounded corners 623, and convex rounded corners 621. Specifically, the radius of the concave rounded corner 622 is 0.8mm to 1.2mm, the radius of the convex rounded corner 623 is 1.8mm to 2.2mm, the radius of the convex rounded corner 621 is 2.8mm to 3.2mm, and the radius of the concave rounded corner is 0.4mm to 0.6mm. These multiple sets of differentiated rounded corner structures, combined with a thickened plate design, can disperse localized stress concentration during the stamping process. This can alleviate material tensile deformation around the mesh and at the transition points of the step, reduce the probability of cracking at the connection between the step sidewall and the mesh, and improve product molding yield and structural stability.

[0040] Combination Figure 13 , Figure 14 In the enlarged section at point B, during step 4 of forming the explosion-proof valve installation sinking step 6, the explosion-proof valve welding step 8 is simultaneously formed circumferentially. The explosion-proof valve welding step 8 sinks approximately 0.55mm to 0.6mm below the upper surface of the front protrusion 3. A raised explosion-proof valve welding angle 81 is formed on the outer side of the explosion-proof valve welding step 8, which meets the welding assembly accuracy requirements of the explosion-proof valve. An assembly area for installing a protective film is formed between the explosion-proof valve welding step 8 and the front protrusion 3. The outer mesh 22 is at least partially arranged at the position of the side wall 62 of the explosion-proof valve installation sinking step to ensure that the side wall has a gas flow channel. Since the explosion-proof valve welding angle 81 is formed last, the problem of corner collapse is avoided.

[0041] Simultaneously, brackets 9 are stamped at both ends of the top cover sheet material 1. The protruding direction of bracket 9 is consistent with the middle recessed step 5. Actual testing by the inventors revealed that directly stamping a complete battery cell bracket can easily lead to tensile cracking at the sidewall position. Therefore, this solution splits the battery cell bracket 9 into a pre-deformation step 91 and a bracket step 92, with the bracket step 92 internally connected to the pre-deformation step 91. The depth of the pre-deformation step 91 is set to 0.6mm to 0.8mm, for example, 0.7mm. During stamping, the sheet metal is pre-stretched and shaped using the pre-deformation step 91, causing a slight deformation at the corresponding position of the top cover sheet and releasing the internal stress of the sheet metal. This pre-deformation structure reduces the material forming resistance during subsequent stamping, allowing for smoother sheet metal deformation during the subsequent stamping of the bracket step 92, effectively reducing the probability of cracking at the bracket sidewall. Furthermore, the inventors specifically optimized the fillet radius parameters of the bracket step 92. The bracket step 92 includes a bracket step platform 921 and a bracket step sidewall 922.

[0042] Combination Figure 19 , Figure 20 The enlarged view at point D shows that the sidewall 922 of the support step is provided with an inner convex fillet 9221, an outer concave fillet 9222, an outer convex fillet 9223, and an inner concave fillet 9224. Specifically, the radius of the inner convex fillet 9221 is 3.3mm to 3.7mm, for example, 3.5mm; the radius of the outer concave fillet 9222 is 0.8mm to 1.2mm, for example, 1mm; the radius of the outer convex fillet 9223 is 1.0mm to 1.4mm, for example, 1.2mm; and the radius of the inner concave fillet 9224 is 1.0mm to 1.4mm, for example, 1.2mm. This fillet parameter design allows for the optimization of the forming structure dimensions of the support step 92, enabling the lower surface of the support step 92 to have a larger support area. This allows for stable contact and support of the battery cell structure, effectively improving the stability of the battery cell support. Simultaneously, it further improves the stress distribution during the support forming process, enhancing the overall forming quality and structural strength of the support.

[0043] To verify the influence of the process parameter range of the present invention on the top cover support portion, multiple sets of examples and comparative examples were set up for stamping forming comparison tests. The forming conditions of each set of tests were the same, and 3003 aluminum alloy was used as the raw material for the top cover. The forming results are shown in the table below.

[0044] As can be seen from the test results in the table above, the present invention can effectively avoid cracking during the stamping process of the bracket by reasonably designing the radius of the bracket fillet and the parameter range of the pre-deformation step depth, thus verifying the rationality of the parameters of the present invention.

[0045] The overall three-dimensional structure after stamping can be referenced. Figure 17The overall top view can be found by referring to Figure 18 In this embodiment, the screen 11 structure is compatible with the stepped structure. The outer edge of the middle recessed step 5 surrounds the central mesh 21, and the central mesh 21 extends at least partially to the side wall 52' of the middle recessed step. The outer edge of the explosion-proof valve mounting recessed step 6 surrounds the outer mesh 22, and the outer mesh 22 is at least partially arranged at the side wall 62 of the explosion-proof valve mounting recessed step. This structure can achieve the anti-clogging and pressure relief function of the integrated screen 11. Simultaneously, with optimized process sequence, plate thickness parameters, and rounded corner structure, both the molding yield and structural support strength can be balanced.

[0046] Existing technologies include some integrated stamping processes for top covers and explosion-proof valves. These processes also employ a sequence of forming the intermediate steps first, followed by the sidewalls of the explosion-proof valve. However, their design philosophy differs from this solution, making them unsuitable for the molding and usage requirements of this product. Traditional integrated explosion-proof valve top cover processes thin the corresponding structural areas to ensure smooth valve opening and pressure relief. This solution, however, uses an integrated screen support structure. This structure relies on various steps to support and limit the battery cells, preventing cell collapse and blockage of the pressure relief channel. Simultaneously, the structure needs to withstand the assembly and working loads of the explosion-proof valve over long periods. Therefore, this structure requires high overall strength, fracture resistance, and structural stability, making thinning a design unsuitable. Existing thin-walled, easily opened integrated explosion-proof valve molding processes are incompatible with the high-strength support design philosophy of this solution and are unsuitable for the molding of this integrated screen top cover. This highlights the design value of this invention, which features thickened sheet metal, optimized corner parameters, and a streamlined process sequence.

[0047] Furthermore, this solution features an integrated screen structure. The structural forming characteristics require that all screen mesh openings 2 be punched in the first step. Pre-punching the mesh openings creates a hollow structure in the sheet metal, disrupting the overall continuity of the metal sheet. This reduces the uniformity of stress transmission within the sheet. During subsequent step stamping, stress concentration easily occurs at the mesh ribs and step sidewalls. Compared to a non-perforated integrated top cover structure, structures with screen openings are more prone to stretching, thinning, tearing, and breakage, making overall forming more difficult. To address this forming challenge, this solution employs a thickened sheet metal design and optimizes the stamping sequence to first form the middle recessed step 5, followed by the explosion-proof valve installation recessed step 6. Simultaneously, multiple sets of differentiated rounded corner structures are used to release localized stress. This structure, in conjunction with the process, mitigates the structural strength weakening caused by pre-punching and compensates for the mechanical defects resulting from screen openings. While meeting the screen's anti-clogging and pressure-relief functions, it also considers stamping yield and finished product structural strength, addressing the industry problem of high-strength integrated forming of pre-punched screen structures.

[0048] It should be noted that the raw material for the top cover sheet described in this invention can also be other grades of aluminum alloy as needed to adapt to the integrated stamping process of multi-step, deep drawing, and screen punching. This invention only limits the stamping process sequence and the structural dimensional parameters. The stamping pressure, holding time, and stamping speed used in the stamping process are all conventional and well-known process parameters in the art. At the same time, there is no special limitation on the stamping direction; forward stamping or reverse stamping is acceptable, and those skilled in the art can flexibly select the appropriate method based on the production equipment.

[0049] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for stamping a top cover sheet, characterized in that, Includes the following steps: Step 1: Punch and cut the top cover sheet material with a thickness of 2.5mm to 3mm to form the screen mesh; Step 2: Stamp the top cover sheet material to form a front convex shape. The screen mesh is arranged in the forming area of ​​the front convex shape. At the same time as stamping the front convex shape, the back of the top cover sheet is correspondingly recessed. Step 3: Stamp a middle recessed step with a depth of 5mm to 5.4mm in the central area of ​​the front protrusion. The middle recessed step includes a middle recessed step platform and an initial middle recessed step sidewall. The lower end of the initial middle recessed step sidewall has an inward concave fillet radius of 0.8mm to 1.2mm and an outward convex fillet radius of 2.8mm to 3.2mm. The thickness of the step surface of the middle recessed step is 2.5mm to 3mm. Step 4: Stamp the initial intermediate sinking step sidewall and its outer edge to form the surrounding explosion-proof valve installation sinking step sidewall and the final intermediate sinking step sidewall, and form an annular explosion-proof valve support platform with a thickness of 2.5mm to 3mm between the intermediate sinking step sidewall and the explosion-proof valve installation sinking step sidewall.

2. The method for stamping and forming the top cover sheet according to claim 1, characterized in that: In step 4, the explosion-proof valve welding step is simultaneously stamped and formed. The explosion-proof valve welding step is arranged around the outside of the side wall of the explosion-proof valve installation sinking step, and the explosion-proof valve welding step forms a raised welding angle. An installation area for assembling the protective film is formed between the explosion-proof valve welding step and the front protrusion.

3. The method for stamping and forming the top cover sheet according to claim 1, characterized in that: The screen mesh formed in step 1 includes a central mesh and an outer mesh. The outer edge of the central sinking step surrounds the central mesh, and the central mesh extends at least partially to the side wall of the central sinking step.

4. The method for stamping and forming the top cover sheet according to claim 3, characterized in that: The outer edge of the explosion-proof valve installation sinking step formed in step 4 surrounds the outer mesh, and the outer mesh is at least partially located on the side wall of the explosion-proof valve installation sinking step.

5. The method for stamping and forming a top cover sheet according to claim 1, characterized in that: In step 4, the connection between the annular explosion-proof valve support platform and the side wall of the middle sinking step is stamped with the following dimensions: inner convex fillet radius of 2.3mm to 2.7mm and outer concave fillet radius of 0.4mm to 0.6mm.

6. The method for stamping and forming a top cover sheet according to claim 1, characterized in that: In step 4, the side wall of the sinking step for installing the explosion-proof valve is stamped with the following dimensions: inner concave fillet radius 0.8mm to 1.2mm, inner convex fillet radius 1.8mm to 2.2mm, outer convex fillet radius 2.8mm to 3.2mm, and outer concave fillet radius 0.4mm to 0.6mm.

7. The method for stamping and forming a top cover sheet according to claim 1, characterized in that, In step 4, battery cell supports are also formed by stamping at both ends of the top cover sheet material. The direction of the protrusion of the battery cell supports is the same as that of the middle recessed step.

8. The method for stamping and forming a top cover sheet according to claim 7, characterized in that, In step 4, the stamped battery cell support includes a pre-deformed step formed simultaneously and a support step connected inside the pre-deformed step.

9. The method for stamping and forming a top cover sheet according to claim 8, characterized in that: The depth of the pre-deformed step is 0.6 mm to 0.8 mm.

10. The method for stamping and forming a top cover sheet according to claim 9, characterized in that: The inner sidewall convex fillet radius of the support step is 3.3mm to 3.7mm, the outer sidewall concave fillet radius is 0.8mm to 1.2mm, and the outer sidewall convex fillet radius is 1.0mm to 1.4mm.

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