Method for manufacturing an electric motorcycle battery pack case

Abstract

This invention discloses a method for manufacturing an electric motorcycle battery pack housing. An integrally extruded aluminum alloy profile is cut and bent to form the main frame structure of the battery pack housing. The profile has two hollow sides, enabling direct bending of the thick-walled sides. This completely eliminates the complex pre-machining and laser welding processes at bends. The hollow structure effectively absorbs and releases stress during bending, preventing cracks and wrinkles. The production process is simplified to "extrusion → cutting → bending → welding," significantly shortening the production cycle. The U-shaped splicing significantly improves the tolerance to bending angle errors, making laser welding easier to align and resulting in more consistent weld penetration. This avoids stress concentration, improves fatigue resistance, and ensures a smooth weld transition without the need for grinding.

Description

Technical Field

[0001] This invention belongs to the field of laser welding technology, and in particular relates to a method for preparing an electric motorcycle battery pack housing. Background Technology

[0002] As a crucial component in electric motorcycles and electric vehicles, the battery pack enclosure primarily provides physical protection, safeguarding the battery pack and ensuring its stability and safety by preventing external shocks, vibrations, and other hazards. Simultaneously, the battery pack enclosure must also be waterproof, dustproof, and lightweight to ensure the battery pack functions properly in harsh environments. The design of the battery pack enclosure not only affects battery safety but also directly impacts the vehicle's weight, range, and overall performance.

[0003] Currently, there are several main methods for manufacturing electric motorcycle battery pack housings: 1. Casting Solution: Casting is completed through integrated mold casting. Its disadvantages include: high mold development costs, long production cycles, and long and costly verification cycles for product design adjustments. Furthermore, uneven oxidation is prone to occur on the surface of cast parts, affecting appearance and subsequent processing.

[0004] 2. Direct Extrusion Solution: Formed using aluminum alloy extrusion technology. To meet the specific wall thickness required for the sealing surface of the enclosure, a uniform overall wall thickness is often necessary, leading to material redundancy in non-critical areas and increasing overall weight and material costs. For this type of solid, thick-walled profile, threaded connection holes are formed by drilling and tapping along the thick-walled side. However, to ensure that the drilling does not penetrate the enclosure wall thickness and avoid creating leakage channels running through the interior and exterior, sufficient safety margin must be reserved. Therefore, the side wall thickness is often designed to be much greater than the actual strength requirements, resulting in material waste and increased weight. In terms of bending, thick-walled materials have poor plastic deformation capacity when directly bent. Cracks easily form on the outer side of the bending area, and wrinkles easily form on the inner side, making it difficult to guarantee bending quality and resulting in a high scrap rate.

[0005] 3. Extrusion + Bending + Laser Welding Solution (e.g., the applicant's patent CN120978313A): This method involves extruding a profile, followed by machining, bending, and laser welding. However, during bending, thick-walled materials have poor plastic deformation capabilities, leading to cracks on the outer side of the bending area and wrinkles on the inner side, making it difficult to guarantee bending quality and resulting in a high scrap rate. Therefore, to facilitate bending, complex machining (such as milling a specific shape) is required at the bending point of the profile. This machining is difficult, time-consuming, and costly. Furthermore, laser welding is still required at the bending point after the profile is bent, making the process still complex. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned problems existing in the prior art and to provide a method for preparing an electric motorcycle battery pack housing.

[0007] The objective of this invention is achieved through the following technical solution: A method for preparing an electric motorcycle battery pack housing includes the following steps: Step 1: Cut and bend the profile to form the main frame structure of the electric motorcycle battery pack box. The profile is an integrally extruded aluminum alloy profile with a plate body and hollow side portions at both ends of the plate body. The thickness of the hollow side portion is greater than the thickness of the plate body. The hollow side portion has one or more cavities extending along the length of the profile. The outer end face of the hollow side portion is provided with a sealing gasket groove extending along the length of the profile. After the profile is bent, its two free ends are arranged parallel to each other, forming a gap between them, and both free ends face and extend into the receiving space of the frame structure; Step 2: Seal the gap using a laser welding strip, wherein the laser welding strip includes a first part and a second part, the width of the first part being greater than the width of the second part; insert the second part into the gap with an interference fit, and use the first part to cover the two free ends of the frame structure, and laser weld to form a frame structure sealed on all four sides; Step 3: At the upper and lower ends of the frame structure, threaded holes are formed in the sealing gasket groove using a hot-melt drilling and tapping process in one step. A high-speed rotating carbide drill bit contacts the wall of the hollow structure at a predetermined position. The high heat generated by friction rapidly softens the local material and puts it into a plastic state. The drill bit penetrates the wall of the hollow side and uses axial pressure to squeeze the softened material to the surrounding area, forming a bushing or boss with increased thickness around the hole. After drilling is completed, threads are directly machined on the bushing or boss through a tapping process to form the threaded hole. Step four: Assemble the base, top cover, and sealing gasket. The top cover has evenly distributed first through holes, and the sealing gasket has the same number and position of second through holes. By passing screws through the first and second through holes and then threading them into the threaded holes, the main body, sealing gasket, and top cover can be fixed together. Similarly, the base has a post hole, and by passing screws through the post hole and the second through hole and then threading them into the threaded holes, the main body, sealing gasket, and base can be fixed together.

[0008] Preferably, the cross-section of the cavity is rectangular, circular, or irregular.

[0009] Preferably, step one includes a shaping step of forming the frame structure into a rectangular or square cross-sectional structure for adapting to the battery pack.

[0010] Preferably, after bending in step one, the sealing groove of the profile is formed to fit the shape of the sealing gasket.

[0011] Preferably, the laser welding strip forms a U-shaped groove on one side of the main body after welding.

[0012] Preferably, the hollow side of the profile has reinforcing ribs between it and the plate.

[0013] Preferably, the threaded hole formed in step three only penetrates the first layer of wall on the outer side of the hollow side, leaving the second layer of wall intact, thus forming a threaded hole with a closed bottom.

[0014] Preferably, the method also includes a pull ring installation step, in which the pull ring is installed onto the outer side of the frame structure of the main body using screws.

[0015] The advantages of this invention are mainly reflected in the following aspects: The profile is an integrally extruded aluminum alloy profile, in which the hollow side significantly improves bending processability. The hollow structure effectively absorbs and releases stress generated by material deformation during bending, greatly enhancing the plastic deformation capacity of the thick-walled side. Compared to solid thick walls, the hollow structure reduces tensile stress on the outer side and compressive stress on the inner side during bending, effectively preventing cracks and wrinkles. This makes the previously difficult-to-process direct bending process possible, completely eliminating the complex pre-machining and laser welding procedures at the bending point. Simultaneously, the hollow structure significantly reduces material usage without sacrificing the moment of inertia and bending stiffness. By optimizing the cavity shape and wall thickness distribution, the weight of the battery pack can be reduced by 10%-15% while maintaining or even improving structural strength, effectively reducing material costs and overall vehicle energy consumption. More importantly, the main frame structure of the electric motorcycle battery pack, manufactured using an integrally extruded aluminum alloy profile, offers better sealing.

[0016] The hot-melt drilling and tapping process creates threaded holes in a single operation. This process penetrates only the first layer of the hollow structure, leaving the second layer intact, resulting in a closed-bottom threaded hole. Compared to traditional solid thick-walled tapping solutions, this method utilizes a double-walled hollow structure and penetrates only the first layer. The second layer naturally forms a sealing barrier, eliminating concerns about drilling through the housing. Therefore, the side wall thickness can be designed according to strength requirements without additional safety margins, reducing material consumption by 10%-15%. Penetrating only the first layer allows for drilling depths that are half or even less than those for solid thick-walled systems, shortening single-hole processing time, reducing tool wear, and improving overall processing efficiency by over 40%. The threaded hole's bottom is sealed by the complete wall surface, with no through-holes, ensuring the housing's airtightness without additional sealing measures.

[0017] After laser welding, a U-shaped groove is formed on one side of the main body. The splicing structure of this U-shaped groove significantly improves the tolerance for bending angle errors near the free end of the profile. Even if there is a certain deviation in bending accuracy, the two free ends can still maintain good fit and form a parallel surface through tooling fixtures, effectively reducing the control difficulty and scrap rate of the bending process. The gap before forming the U-shaped groove provides a wider butt joint area, making it easier for the laser beam spot to align with the center of the joint during laser welding. The molten pool flows evenly, the weld formation is beautiful, and the penetration depth is consistent, greatly reducing welding defects such as weld deviation and lack of fusion, and significantly improving welding quality and stability. Attached Figure Description

[0018] Figure 1 : A three-dimensional schematic diagram of the battery pack housing of the electric motorcycle of the present invention; Figure 2 : A three-dimensional schematic diagram of the battery pack housing of the electric motorcycle of the present invention in a second direction; Figure 3 : A three-dimensional schematic diagram of the electric motorcycle battery pack housing after the top cover has been removed; Figure 4 : Exploded view of the battery pack housing of the electric motorcycle of this invention; Figure 5 : A three-dimensional schematic diagram of the laser welding electrode of the present invention in the second direction; Figure 6 This invention provides a three-dimensional schematic diagram of the profile used to manufacture the main body of an electric motorcycle battery pack. Figure 7 : Figure 6 Cross-sectional view of medium-sized profile; Figure 8 Cross-sectional view of the second embodiment of the profile of the present invention. Detailed Implementation

[0019] The objectives, advantages, and features of this invention will be illustrated and explained through the following non-limiting description of preferred embodiments. These embodiments are merely typical examples of applying the technical solutions of this invention, and all technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by this invention.

[0020] In the description of the solution, it should be noted that the terms "center," "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience and simplification of 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 the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] This invention discloses a method for preparing an electric motorcycle battery pack housing.

[0022] like Figures 1 to 4 As shown, the electric motorcycle battery pack housing includes a main body 1 integrally formed by a profile 100, and an upper cover 3 and a base 2 fixed to the upper and lower sides of the main body 1 by screws 11. The main body 1, the upper cover 3 and the base 2 form a receiving space for accommodating the battery pack. One side of the main body 1 is a U-shaped groove 10, and the corresponding other side is provided with a pull ring 4, which can play a lifting role.

[0023] The profile 100 is an integrally extruded aluminum alloy profile. After being cut and bent, it forms the frame structure of the main body 1 of the electric motorcycle battery pack box. After the profile 100 is bent, its two free ends are arranged parallel to each other, with a gap 6 between them. Both free ends face and extend into the receiving space.

[0024] The gap 6 is sealed using a laser welding strip 7. Figure 5 As shown, the laser welding strip 7 includes a first part 8 and a second part 9, where the width of the first part 8 is greater than the width of the second part 9. The second part 9 is interference-fitted into the gap 6, and the first part 8 is used to cover the two free ends of the frame structure, which are then laser welded to form a sealed structure.

[0025] After bending, the sealing groove 104 of the profile 100 will also form a shape to fit the sealing gasket 5. A sealing gasket 5 is placed in each of the upper and lower sealing grooves 104 to improve the sealing effect. The fixing structure of the sealing gasket 5 will be described later.

[0026] like Figure 6 , Figure 7 As shown, the profile 100 has a plate body 101 and hollow side portions 102 located at both ends of the plate body. The thickness of the hollow side portions 102 is greater than the thickness of the plate body 101. One or more cavities 103 extending along the length of the profile are provided inside the hollow side portions 102. The cross-section of the cavity 103 can be rectangular, circular, or irregular. A sealing groove 104 extending along the length of the profile is provided on the outer end face of the hollow side portions 102. Alternatively, to increase strength, such as... Figure 8 In the second embodiment of the profile 100 shown, a reinforcing rib 106 is provided between the hollow side portion 102 and the plate body 101.

[0027] The method for preparing the battery pack housing of the electric motorcycle of the present invention includes the following steps: Step 1: Cut and bend the profile 100 to form the frame structure of the main body 1 of the electric motorcycle battery pack box. The profile 100 is an integrally extruded aluminum alloy profile with a plate 101 and hollow side portions 102 located at both ends of the plate. The thickness of the hollow side portion 102 is greater than the thickness of the plate 101. The hollow side portion 102 has one or more cavities 103 extending along the length of the profile inside. The outer end face of the hollow side portion 102 is provided with a sealing gasket groove 104 extending along the length of the profile. After being bent, the profile 100 has two free ends arranged parallel to each other, forming a gap 6 between them. Both free ends face and extend into the receiving space of the frame structure. The sealing groove 104 of the profile 100 is shaped to fit the sealing gasket 5.

[0028] Step one may also optionally include a shaping step to form the frame structure into a rectangular or square cross-sectional structure for adapting to the battery pack.

[0029] Step two, a laser welding strip 7 is used to seal the gap 6, wherein the laser welding strip 7 includes a first part 8 and a second part 9, the width of the first part 8 is greater than the width of the second part 9; the second part 9 is inserted into the gap 6 with an interference fit, and the first part 8 is used to cover the two free ends of the frame structure, and laser welding is performed to form a frame structure that is sealed on all four sides.

[0030] Step 3: At the upper and lower ends of the frame structure, threaded holes 105 are formed in the sealing gasket groove 104 using a hot-melt drilling and tapping process in one step. A high-speed rotating carbide drill bit contacts the wall of the hollow structure at a predetermined position. The high heat generated by friction rapidly softens the local material and puts it into a plastic state. The drill bit penetrates the wall of the hollow side 102 and uses axial pressure to squeeze the softened material outwards, forming a bushing or boss with increased thickness around the hole. After drilling is completed, threads are directly machined on the bushing or boss through a tapping process to form the threaded hole 105. The threaded hole 105 only penetrates the first layer of the outer wall of the hollow side 102, leaving the second layer of the wall intact, forming a threaded hole with a closed bottom.

[0031] Step four: Assemble the base 2, top cover 3, and sealing gasket 5. The top cover 3 has evenly distributed first through holes 12, and the sealing gasket 5 has the same number and position of second through holes 14. By using screws 11 to pass through the first through holes 12 and the second through holes 14 and then threaded into the threaded hole 105, the main body 1, sealing gasket 5, and top cover 3 can be fixed together. Similarly, the base 2 has a post hole 13. By using screws 11 to pass through the post hole 13 and the second through hole 14 and then threaded into the threaded hole 105, the main body 1, sealing gasket 5, and base 2 can be fixed together.

[0032] Step 5: Assemble the pull ring 4 by attaching the pull ring 4 to the outer side of the frame structure of the main body 1 using screws.

[0033] In this invention, the profile is an integrally extruded aluminum alloy profile with a hollow structure on its side, and a sealing gasket groove is pre-reserved directly on the extruded profile. This hollow structure significantly improves bending processability. During bending, the hollow structure effectively absorbs and releases the stress generated by material deformation, greatly enhancing the plastic deformation capacity of the thick-walled side. Compared to solid thick walls, the hollow structure reduces the tensile stress on the outer side and the compressive stress on the inner side during bending, effectively avoiding the generation of cracks and wrinkles. This makes the previously difficult-to-process direct bending process possible, completely eliminating the complex pre-machining and laser welding processes at bends. At the same time, the hollow structure significantly reduces material usage without sacrificing the moment of inertia and bending stiffness of the cross-section. By optimizing the cavity shape and wall thickness distribution, the weight of the box can be reduced by 10%-15% while maintaining or even improving structural strength, effectively reducing material costs and overall vehicle energy consumption. Furthermore, the mechanical properties of the hollow structure mean that its bending section modulus is only slightly lower than that of a solid structure of the same dimensions. By rationally designing the cavity shape and reinforcing ribs, its stiffness in specific stress directions can even be superior to that of a solid structure, ensuring the overall structural strength and impact resistance of the box. Because direct bending is achieved, the production process is simplified to "extrusion → cutting → bending → welding," reducing process steps, equipment investment, and labor costs, significantly shortening the production cycle, and substantially improving product consistency and reliability.

[0034] In this invention, a hot-melt drilling and tapping process is used to form threaded holes in one step. This process only penetrates the outermost first layer of the hollow structure, leaving the second layer intact, thus forming a threaded hole with a closed bottom. Compared with the traditional solid thick-walled tapping solution, because a double-walled hollow structure is used and only the first layer is penetrated, the second layer naturally forms a sealing barrier, eliminating any concerns about drilling through the housing. Therefore, the side wall thickness can be designed according to strength requirements without adding an extra safety margin, reducing material consumption by 10%-15%. Since only the first layer needs to be penetrated, the drilling depth is half or even less than that of a solid thick-walled structure, shortening single-hole processing time, reducing tool wear, and improving overall processing efficiency by more than 40%. The bottom of the threaded hole is sealed by the complete wall, with no channel penetrating inside or outside, ensuring the airtightness of the housing without additional sealing measures.

[0035] In this invention, the laser welding strip 7 forms a U-shaped groove 10 on one side of the main body 1 after welding. The splicing structure of this U-shaped groove significantly improves the tolerance for bending angle errors near the free end of the profile. Even if there is a certain deviation in bending accuracy, the two free ends can still maintain good fit and form a parallel surface through the tooling fixture, effectively reducing the control difficulty and scrap rate of the bending process. The gap before forming the U-shaped groove provides a wider butt joint area, making it easier for the laser beam spot to align with the center of the joint during laser welding. The molten pool flows evenly, the weld formation is beautiful, and the penetration depth is consistent, greatly reducing welding defects such as weld deviation and lack of fusion, and significantly improving welding quality and stability.

[0036] Existing technologies employ a V-shaped splicing structure, which demands extremely high precision in bending angles. Even slight deviations in the bending angle can prevent the V-shaped surfaces of the two materials from fitting tightly, resulting in localized gaps or misalignments. During laser welding of the V-shaped joint, the narrow and sharp-angled joint makes it difficult to stably focus the laser beam at the joint center, easily leading to welding defects such as weld misalignment and incomplete fusion. The sharp corners of the V-shaped joint are prone to stress concentration points after welding, potentially initiating fatigue cracks under long-term vehicle vibration and impact loads. Furthermore, V-shaped joints often require grinding after welding, increasing post-processing steps and manufacturing costs. The U-shaped joint design of this invention effectively avoids the stress concentration at the sharp corners of the original V-shape, resulting in a more uniform stress distribution in the joint area. Under the same load conditions, the fatigue resistance of the joint is significantly improved, enhancing the structural strength and long-term reliability of the housing. The weld seam itself is smooth after U-shaped splicing welding, generally requiring no additional grinding, simplifying the production process and reducing manufacturing costs.

[0037] Therefore, this invention significantly improves welding quality, sealing performance, and structural strength while simplifying the process, increasing efficiency, and reducing costs.

[0038] This invention has many other embodiments, such as changing the processing and manufacturing sequence. All technical solutions formed by equivalent transformation or equivalent transformation fall within the protection scope of this invention.

Claims

1. A method of manufacturing an e-mobility battery pack housing, characterized in that: Includes the following steps, Step 1: Cut and bend the profile (100) to form the frame structure of the main body (1) of the electric motorcycle battery pack box. The profile (100) is an integrally extruded aluminum alloy profile with a plate (101) and hollow side portions (102) located at both ends of the plate. The thickness of the hollow side portion (102) is greater than the thickness of the plate (101). The hollow side portion (102) has one or more cavities (103) extending along the length of the profile inside. The outer end face of the hollow side portion (102) is provided with a sealing gasket groove (104) extending along the length of the profile. After the profile (100) is bent, its two free ends are arranged parallel to each other, forming a gap (6) between them. Both free ends face and extend into the receiving space of the frame structure. Step 2: Use a laser welding strip (7) to seal the gap (6), wherein the laser welding strip (7) includes a first part (8) and a second part (9), the width of the first part (8) is greater than the width of the second part (9); insert the second part (9) into the gap (6) with an interference fit, and use the first part (8) to cover the two free ends of the frame structure, and laser weld to form a frame structure sealed on all sides; Step 3: At the upper and lower ends of the frame structure, threaded holes (105) are formed in the sealing gasket groove (104) using a hot melt drilling and tapping process. A high-speed rotating carbide drill bit is used to contact the wall of the hollow structure at a predetermined position. The high heat generated by friction causes the local material to soften rapidly and become plastic. The drill bit penetrates the wall of the hollow side (102) and uses axial pressure to squeeze the softened material to the surrounding area, forming a bushing or boss with increased thickness around the hole. After the drilling is completed, the thread is directly machined on the bushing or boss through a tapping process to form the threaded hole (105). Step 4: Assemble the base (2), the top cover (3), and the sealing gasket (5). The top cover (3) has evenly distributed first through holes (12), and the sealing gasket (5) has the same number and position of second through holes (14). By using screws (11) to pass through the first through holes (12) and the second through holes (14) and then threaded to the threaded hole (105), the main body (1), the sealing gasket (5), and the top cover (3) can be fixed together. Similarly, the base (2) has a post hole (13). By using screws (11) to pass through the post hole (13) and the second through hole (14) and then threaded to the threaded hole (105), the main body (1), the sealing gasket (5), and the base (2) can be fixed together.

2. The method of claim 1, wherein: The cross-section of the cavity (103) is rectangular, circular, or irregular.

3. The method for preparing the battery pack housing for electric motorcycles according to claim 1, characterized in that: Step one includes shaping the frame structure into a rectangular or square cross-sectional structure for fitting the battery pack.

4. The method for preparing the battery pack housing for electric motorcycles according to claim 1, characterized in that: After bending in step one, the sealing groove (104) of the profile (100) forms a shape that matches the sealing gasket (5).

5. The method for preparing the battery pack housing for electric motorcycles according to claim 1, characterized in that: After the laser welding strip (7) is welded, it forms a U-shaped groove (10) on one side of the main body (1).

6. The method for preparing the battery pack housing for electric motorcycles according to claim 1, characterized in that: The hollow side (102) of the profile (100) has a reinforcing rib (106) between it and the plate (101).

7. The method for preparing the battery pack housing of an electric motorcycle according to claim 1, characterized in that: The threaded hole (105) formed in step three only penetrates the first layer of wall on the outer side of the hollow side (102), leaving the second layer of wall intact, thus forming a threaded hole with a closed bottom.

8. The method for preparing the battery pack housing of an electric motorcycle according to claim 1, characterized in that: It also includes the installation step of the pull ring (4), which is installed onto the outer side of the frame structure of the main body (1) by screws.

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