A laser welding bulging tooling for large-section thin-walled cavity battery casings for electric bicycles

Abstract

This utility model relates to the field of battery welding technology, specifically a laser welding expansion fixture for large-section thin-walled cavity battery shells for electric bicycles. It mainly includes a worktable, a top clamping device, side clamping devices, and an expansion device. The worktable is welded from a tabletop and several square tubes. The expansion device is fixed to the center of the tabletop, the top clamping device is fixed to the four corners of the tabletop on the outside of the expansion device, and the side clamping devices are fixed to the four opposite sides of the tabletop. This utility model, through the triple synergy of internal expansion, side clamping, and top clamping, comprehensively controls structural deformation during the welding process. It also employs a staged welding process in conjunction with the fixture to achieve minimal deformation welding, effectively solving the deformation control problem in laser welding of large-section thin-walled cavity battery shells. This not only improves welding quality and production efficiency but also provides technical reference for welding similar thin-walled components, showing broad application prospects in the battery manufacturing field.

Description

Technical Field

[0001] This utility model relates to the field of battery welding technology, specifically a laser welding expansion tooling for large-section thin-walled cavity battery shells for electric bicycles. Background Technology

[0002] New energy electric bicycles (including electric-assisted bicycles, electric motorcycles, etc.) are becoming increasingly popular in urban commuting and short-distance travel due to their lightness, environmental friendliness, and energy saving. Their power source is mostly a detachable lithium-ion battery pack, which is usually composed of multiple thin-walled square battery shells (square cells) or cylindrical batteries.

[0003] Compared to the bulky battery packs of electric vehicles, e-bike battery cases generally have the following characteristics: 1. Smaller size. To fit the vehicle's structure, battery packs are typically designed to be more compact. 2. Potentially thinner walls. For weight reduction and cost considerations, some e-bike battery cases may have thinner walls. 3. Still need a robust structure. They must withstand vibrations during riding, occasional minor impacts, and possess a certain level of dust and water resistance (e.g., IPX4 / IPX5 rating). 4. High sealing requirements. To prevent electrolyte leakage or moisture intrusion, ensuring battery safety and lifespan.

[0004] Therefore, laser welding technology, with its advantages of concentrated energy, small heat-affected zone, high processing precision, and ease of automation, has been widely used in the manufacturing of lithium-ion batteries. In the welding of electric bicycle battery casings, it is mainly used for sealing the battery casing with the base plate / cover plate, welding explosion-proof valves, and welding electrode posts.

[0005] However, significant challenges remain during the welding process, especially when dealing with battery casings of large cross-section, thin-walled, hollow structures: 1. Aluminum alloy material characteristics. Over 90% of the battery casing is made of aluminum alloy. Aluminum has extremely high laser reflectivity, making it highly sensitive to porosity during welding, easily leading to thermal cracking and spatter (explosion). 2. Thin-walled structures are prone to deformation. The heat generated during laser welding causes thermal deformation of the thin-walled casing. This deformation is more pronounced for large cross-section hollow structures, potentially leading to dimensional inaccuracies, poor sealing, and even battery casing expansion after welding. 3. High assembly requirements. For square batteries, especially at corners (R-corners), the precision of the incoming materials is crucial during welding; otherwise, welding defects are likely to occur.

[0006] Analysis of existing technologies reveals that most improvements are made to the battery casing structure, welding process, or external clamping fixtures. However, there is a lack of fixture designs specifically designed to resist internal expansion and deformation during laser welding of large-section, thin-walled, hollow battery casings. Utility Model Content

[0007] To address the aforementioned issues, this invention provides a laser welding bulging fixture for large-section thin-walled cavity battery shells for electric bicycles. It proposes an integrated multi-layered anti-deformation structure, employing a triple synergistic effect of internal bulging, side clamping, and top pressing to comprehensively control structural deformation during the welding process. A staged welding process (battery shell placement → internal bulging → side clamping → placement of base plate → top pressing → laser scanning → segmented welding → releasing the top → full-circle welding → battery shell) is used in conjunction with the fixture to achieve minimal deformation welding. This effectively solves the deformation control problem in laser welding of large-section thin-walled cavity battery shells, improving welding quality and production efficiency. It also provides technical reference for welding similar thin-walled components and has broad application prospects in the field of new energy electric bicycle power battery manufacturing.

[0008] To achieve the above objectives, the technical solution of this utility model is as follows:

[0009] A laser welding expansion tooling for a large-section thin-walled cavity battery shell for electric bicycles mainly includes a worktable, a top clamping device, a side clamping device, and an expansion device. The worktable is welded from a table panel and several square tubes. The expansion device is fixed in the middle of the table panel. The top clamping device is fixed on the table panel at the four corners of the outer side of the expansion device. The side clamping device is fixed on the table panel directly opposite the expansion device.

[0010] The top of the expansion device is a top plate. Bolts pass through the countersunk holes in the top plate, the through holes in the middle of the support column, and the corresponding threaded holes in the middle pad plate for threaded connection. Above the middle pad plate are expansion slide rail 1, expansion slide rail 2, expansion slide rail 3, expansion slide rail 4, and expansion slider. The slide rails in each direction are placed facing the center and wedge-shaped with the slide rail grooves of the expansion slider. Several support plates are provided below the middle pad plate, and several bottom pads are placed below the support plates. The bottom pads are fixed to the table plate with bolts. The expansion cylinder is installed below the table plate. The piston rod of the expansion cylinder passes through the table plate, bottom pad, and middle pad in sequence from bottom to top and is bolted to the piston rod connection hole of the expansion slider. By pulling down the piston rod, the expansion slider moves downward, thereby driving the expansion slide rails in each direction to expand outward synchronously and evenly, opening up the inner wall of the battery shell. By applying support force from inside the battery casing through the expansion device, the tendency of the thin wall to deform inward due to welding thermal stress is directly countered. This is a key function that existing external clamping fixtures cannot achieve.

[0011] By using an internal expansion slide rail and slider mechanism, the inner wall of the battery casing is expanded from the inside before welding, directly resisting the tendency of the thin wall to deform inward due to welding thermal stress. This is fundamentally different from existing tooling that only clamps from the outside. Combined with the side clamping device and the top pressing device, it forms a triple anti-deformation mechanism of "internal and external clamping and top and bottom coordination" with the internal expansion mechanism, achieving comprehensive constraint on the battery casing and the base plate. Compared with the single anti-deformation measures in the existing technology, this utility model innovatively proposes an integrated multi-anti-deformation structure, which comprehensively controls the structural deformation during the welding process through the synergistic effect of internal expansion, side clamping and top pressing.

[0012] The top clamping device mainly includes a top clamping cylinder, a top clamping cylinder base, and a top clamping block. The top clamping cylinder base is inverted π-shaped, and its bottom is fixed to the table with bolts and nuts. The top of the top clamping cylinder base has several threaded holes for bolt connection to the top clamping cylinder. The piston rod of the top clamping cylinder has a threaded hole for bolt connection to one end of the top clamping block. The top clamping device ensures full contact between the battery casing bottom plate and the casing, providing uniform and consistent mating conditions for laser welding and avoiding welding defects caused by poor fit. The inverted π-shaped design of the top clamping cylinder base ensures sufficient rigidity and stability, provides the required height for top clamping, and also has a certain weight-reduction effect.

[0013] The side clamping device mainly includes a side clamping cylinder, a side clamping cylinder base, and a side clamping block. The side clamping cylinder base is L-shaped, and its bottom is fixed to the table with bolts and nuts. The upper part of the side clamping cylinder base has several threaded holes for bolt connection to the side clamping cylinder. The baffle of the side clamping cylinder has several through holes for bolt connection to the side clamping block. The side clamping device applies constraint force from the outside of the battery casing, creating an "inner and outer clamping" effect with the internal expansion, effectively suppressing overall deformation during welding. The L-shaped design of the side clamping cylinder base provides a stable support foundation for side clamping, ensuring that the clamping force is directly and effectively transmitted to the battery casing.

[0014] Expansion-type slide rails 1, 2, 3, and 4 all have slide rails of the same size, with a thickness less than the height of the support column. The slide rails are serrated and form a certain angle with the vertical direction. The four sides of the expansion-type slider have serrated slide rail grooves, also at a certain angle with the vertical direction, and the slide rails and grooves are wedge-shaped. The expansion-type slider has piston rod connection holes and support column through holes on its top and bottom surfaces. The slide rail thickness is less than the height of the support column to prevent the top plate from pressing on the slide rail and affecting its normal movement. The wedge-shaped fit design of the slide rail and slide rail groove ensures that when the expansion slider moves downward, it can simultaneously push the expansion slide rails in multiple directions outward, thereby evenly expanding the inner wall of the battery casing. This uniform support and effective deformation control provide a foundation for ensuring the airtightness of the weld, significantly improving the weld airtightness qualification rate. Simultaneously, the wedge-shaped fit design also ensures that when the expansion cylinder pushes back to its original position after welding, the expansion slide rails uniformly contract inward, smoothly detaching from the welded product, allowing for easy removal of the welded product and greatly improving production efficiency and operational convenience. The advantages of the serrated slide rail and serrated groove combination are mainly reflected in high load-bearing capacity, self-locking performance, and compact structure, making it suitable for mechanical scenarios requiring stable guidance and impact resistance.

[0015] Bottom mounting blocks are bolted to the four sides of the upper part of the bottom pad; the bottom mounting blocks, expansion slide rail one, expansion slide rail two, expansion slide rail three, and expansion slide rail four all have chamfers above their contact surfaces with the inner wall of the battery casing. This chamfer design serves both as a guide and as a prevents scratching the inner wall of the battery casing.

[0016] The piston rod of the expansion cylinder has a threaded hole at the top for bolting the piston rod to the expansion slider, so that the expansion slider can move downward synchronously when the piston rod is pulled down.

[0017] The tabletop has several through holes for air pipes, bolts, and piston rods. The air pipe through holes are used to organize the air pipes of nearby cylinders, allowing them to pass through the bottom of the tabletop and connect to the air source from underneath, keeping the tabletop clean and tidy, facilitating laser welding operations and subsequent maintenance. The bolt through holes are used to connect and secure the bases and bottom pads of each cylinder. The piston rod through holes allow the piston rods at the bottom of the tabletop to pass through and connect to the relevant components above the tabletop.

[0018] The battery casing includes the battery housing and the battery housing base plate. The battery housing base plate is stamped and formed with steps on the edges to facilitate better airtightness after laser welding with the battery housing.

[0019] The specific process flow of this utility model laser welding expansion tooling is as follows: First, the battery casing is fitted into the middle of the tooling. Then, the expansion cylinder is activated to pull down and drive the expansion slider to move downward in a straight line. The expansion slider then drives the four side expansion rails to move outward synchronously to open the inner wall of the battery casing. Next, the side clamping device is activated to hold the outer wall of the battery casing. Then, the battery casing bottom plate is placed on top of the battery casing. Then, the top pressing device is activated to press the battery casing bottom plate. Then, the battery casing bottom plate is tapped evenly and lightly with a rubber hammer to make it fully contact and fit flat with the battery casing. Then, the laser welding robot is activated to scan the entire welding area of ​​the battery casing (to assist in positioning and correction). Then, a small part of the middle of the four sides of the battery casing bottom plate is laser welded. Then, the top pressing device is released. Finally, the laser welding is activated again to weld the entire outer ring of the battery casing bottom plate. After the welding is completed, the expansion device is released, the expansion cylinder is reset upward, and the welded battery casing can be easily removed. In brief: Insert the battery casing → internal expansion → side clamping → insert the base plate → top pressing → laser scanning → segmented welding → loosen the top → full-circle welding → battery casing.

[0020] By first performing small-scale laser welding on the center of the four sides of the battery casing base plate while it is under top clamping, initial fixation is achieved. Then, the top clamping device is released to release some of the welding stress on the battery casing. Finally, the entire circle is welded to reduce final deformation. This phased welding and stress release strategy can effectively control residual stress and final deformation, elevating the tooling from a simple "positioning" tool to a "deformation manager".

[0021] Advantages of utility models:

[0022] 1. This utility model proposes an integrated multi-layer anti-deformation structure, which comprehensively controls structural deformation during the welding process through the triple synergistic effect of internal expansion, side clamping, and top pressing. Compared with the single anti-deformation measures in the prior art, this utility model can significantly improve the flatness, dimensional accuracy, and airtightness of the welded battery casing compared to the current industry level.

[0023] 2. This utility model designs a dynamic adaptive expansion system, which achieves uniform distribution and precise control of expansion force through ingenious mechanical structure: (1) The wedge-shaped fit design of the multi-slider slide rail group ensures that when the expansion slider moves downward, it can simultaneously push the expansion slide rails in multiple directions to move outward, thereby uniformly expanding the inner wall of the battery shell. The uniform support and effective deformation control provide a basis for ensuring the airtightness of the weld, greatly improving the pass rate of the airtightness of the weld; at the same time, the wedge-shaped fit design can also ensure that when the expansion cylinder is pushed up and reset after welding, the expansion slide rails uniformly contract inward and smoothly detach from the welded product, so that the welded product can be easily removed, greatly improving production efficiency and operational convenience; (2) The expansion cylinder can precisely control the movement stroke of the expansion slider through the piston rod, realize the fine adjustment of the expansion force, and avoid excessive force causing damage to the battery shell or insufficient force to effectively support it.

[0024] 3. This utility model organically combines the welding process sequence (placing the battery casing → internal expansion → side clamping → placing the base plate → top pressing → laser scanning → segmented welding → loosening the top → full-circle welding → battery casing) with tooling operations. By effectively controlling residual stress and deformation through staged welding, it can achieve welding with minimal deformation. Attached Figure Description

[0025] Figure 1 This is an elevation view of the present invention before expansion (excluding the battery casing).

[0026] Figure 2 This is an elevation view of the structure of this utility model during its expansion process; (including the battery casing).

[0027] Figure 3 This is a top view of the expanded form of this utility model; (including the battery casing).

[0028] Figure 4 This is a right view of the expanded form of this utility model; (including the battery casing).

[0029] Figure 5 for Figure 3 Partial sectional view along the AA direction (including battery casing);

[0030] Figure 6 for Figure 4 Cross-sectional view along the BB direction (including battery casing);

[0031] Figure 7 for Figure 1 A magnified view of a section at point I;

[0032] Figure 8 This is an elevation view of the expansion-type slide rail of this utility model;

[0033] Figure 9 This is an elevation view of the expansion-type slider of this utility model;

[0034] Figure 10 This is an elevation view of the finished battery casing of this utility model;

[0035] The serial numbers and component names in the diagram are as follows: 1-Workbench; 11-Square tube; 12-Tabletop; 121-Air pipe through hole; 2-Top clamping device; 21-Top clamping cylinder; 22-Top clamping cylinder base; 23-Top clamping block; 3-Side clamping device; 31-Side clamping cylinder; 32-Side clamping cylinder base; 33-Side clamping block; 4-Expansion device; 41-Expansion cylinder; 42-Piston rod; 421-Connecting screw 43 - Expansion rail one; 44 - Expansion rail two; 45 - Expansion rail three; 46 - Expansion rail four; 47 - Expansion slider; 471 - Rail groove; 472 - Piston rod connection hole; 473 - Support column through hole; 48 - Bottom pad; 481 - Bottom bonding block; 49 - Support plate; 410 - Middle pad; 411 - Top plate; 4111 - Support column; 5 - Battery casing; 51 - Battery casing; 52 - Battery casing bottom plate. Detailed Implementation

[0036] To provide a more detailed description of this utility model, the following description, in conjunction with the embodiments and accompanying drawings, will further illustrate this utility model.

[0037] Example 1

[0038] like Figure 1-4 As shown, a laser welding expansion tooling for a large-section thin-walled cavity battery shell for electric bicycles mainly includes a worktable 1, a top clamping device 2, a side clamping device 3, and an expansion device 4. The worktable 1 is welded from a table panel 12 and several square tubes. The expansion device 4 is fixed in the middle of the table panel 12. The top clamping device 2 is fixed on the table panel 12 at the four corners of the outer side of the expansion device 4. The side clamping device 3 is fixed on the table panel 12 directly opposite the expansion device 4.

[0039] like Figure 5-7As shown, the top of the expansion device 4 is a top plate 411. Bolts pass through the countersunk holes of the top plate 411, the central through hole of the support column 4111, and the corresponding threaded holes on the central pad 410 for threaded connection. Expansion slide rails 43, 44, 45, 46, and 47 are installed above the central pad 410. The slide rails of each direction are positioned towards the center and wedge-shaped into the slide rail grooves 471 of the expansion slider 47. Several... A dry support plate 49 is provided, and several bottom pads 48 are placed under the support plate 49. The bottom pads 48 are fixed to the table plate 12 by bolts. An expansion cylinder 41 is installed under the table plate 12. The piston rod 42 of the expansion cylinder 41 passes through the table plate 12, the bottom pad 48, and the middle pad 410 from bottom to top and is bolted to the piston rod connection hole 472 of the expansion slider 47. The expansion slider 47 moves downward by pulling down the piston rod 42, which in turn drives the expansion slide rails in all directions to expand outward synchronously and evenly, opening up the inner wall of the battery shell 5.

[0040] like Figure 1 As shown, the top pressing device 2 mainly includes a top pressing cylinder 21, a top pressing cylinder base 22, and a top pressing block 23. The top pressing cylinder base 22 is inverted π-shaped. The bottom of the top pressing cylinder base 22 is fixed to the table 12 with bolts and nuts. The top of the top pressing cylinder base 22 is provided with several threaded holes that are bolted to the top pressing cylinder 21. The top of the piston rod of the top pressing cylinder 21 is provided with a threaded hole that is bolted to one end of the top pressing block 23.

[0041] like Figure 1 As shown, the side clamping device 3 mainly includes a side clamping cylinder 31, a side clamping cylinder base 32, and a side clamping block 33. The side clamping cylinder base 32 is L-shaped, and the bottom of the side clamping cylinder base 32 is fixed to the table 12 with bolts and nuts. The upper part of the side clamping cylinder base 32 is provided with several threaded holes that are bolted to the side clamping cylinder 31. The baffle of the side clamping cylinder 31 is provided with several through holes that are bolted to the side clamping block 33.

[0042] like Figure 6-8 As shown, the expansion slide rail 1 43, expansion slide rail 2 44, expansion slide rail 3 45, and expansion slide rail 46 are all equipped with slide rails of the same size. The thickness of each slide rail is less than the height of the support column 4111. The slide rails are serrated and form a certain angle with the vertical direction.

[0043] like Figure 9 As shown, the expansion slider 47 has serrated slide rail grooves 471 on all four sides, and the slide rail grooves 471 also form a certain angle with the vertical direction. The slide rail and the slide rail grooves 471 are wedge-shaped. The expansion slider 47 has piston rod connecting holes 472 and support column through holes 473 on the upper and lower surfaces.

[0044] like Figure 1 As shown, bottom mounting blocks 481 are bolted to the four sides of the upper end of the bottom pad 48; the bottom mounting blocks 481, expansion slide rail one 43, expansion slide rail two 44, expansion slide rail three 45, and expansion slide rail four 46 are all provided with chamfers above the surfaces of the surfaces that are in contact with the inner wall of the battery casing 51.

[0045] like Figure 5 As shown, the piston rod 42 of the expansion cylinder 41 is provided with a connecting threaded hole 421 at its top end.

[0046] like Figure 1-3 As shown, the tabletop 12 has several air pipe through holes 121, bolt through holes and piston rod through holes on its upper surface.

[0047] like Figure 2 and Figure 10 As shown, the battery casing 5 includes a battery casing 51 and a battery casing base plate 52. After the battery casing base plate 52 is stamped, steps are provided on the edges to facilitate better airtightness after laser welding with the battery casing 51.

Claims

1. A laser welding bulging fixture for a large-section thin-walled cavity battery casing for electric bicycles, characterized in that: It mainly includes a workbench (1), a top pressing device (2), a side clamping device (3) and an expansion device (4). The workbench (1) is made of a tabletop (12) and several square tubes welded together. The expansion device (4) is fixed in the middle of the tabletop (12). The top pressing device (2) is fixed on the tabletop (12) at the four corners of the expansion device (4). The side clamping device (3) is fixed on the tabletop (12) at the four opposite sides of the expansion device (4). The top of the expansion device (4) is a top plate (411). Bolts are threaded through the countersunk hole of the top plate (411), the through hole in the middle of the support column (4111), and the corresponding threaded hole on the middle pad (410). The middle pad (410) is equipped with expansion slide rail one (43), expansion slide rail two (44), expansion slide rail three (45), expansion slide rail four (46), and expansion slider (47). The slide rails of each direction are placed towards the center and wedge-shapedly engaged with the slide rail groove (471) of the expansion slider (47). Several support plates are provided below the middle pad (410). (49) Several bottom pads (48) are placed under the support plate (49). The bottom pads (48) are fixed to the table (12) by bolts. The expansion cylinder (41) is installed under the table (12). The piston rod (42) of the expansion cylinder (41) passes through the table (12), bottom pad (48), and middle pad (410) from bottom to top and is bolted to the piston rod connection hole (472) of the expansion slider (47). The expansion slider (47) moves downward by pulling down the piston rod (42), thereby driving the expansion slide rails in all directions to expand outward synchronously and evenly to open the inner wall of the battery shell (5).

2. The laser welding bulging tooling for the large cross-section thin-walled cavity battery case of the electric bicycle according to claim 1, characterized in that: The top pressing device (2) mainly includes a top pressing cylinder (21), a top pressing cylinder base (22), and a top pressing block (23). The top pressing cylinder base (22) is inverted π-shaped. The bottom of the top pressing cylinder base (22) is fixed to the table (12) with bolts and nuts. The top of the top pressing cylinder base (22) is provided with several threaded holes that are bolted to the top pressing cylinder (21). The top of the piston rod of the top pressing cylinder (21) is provided with a threaded hole that is bolted to one end of the top pressing block (23).

3. The laser welding bulging tooling for the large cross-section thin-walled cavity battery case of the electric bicycle according to claim 1, characterized in that: The side clamping device (3) mainly includes a side clamping cylinder (31), a side clamping cylinder base (32), and a side clamping block (33). The side clamping cylinder base (32) is L-shaped. The bottom of the side clamping cylinder base (32) is fixed to the table (12) with bolts and nuts. The upper part of the side clamping cylinder base (32) is provided with several threaded holes that are bolted to the side clamping cylinder (31). The baffle of the side clamping cylinder (31) is provided with several through holes that are bolted to the side clamping block (33).

4. The laser welding bulging fixture for large-section thin-walled cavity battery casings for electric bicycles according to claim 1, characterized in that: The expansion slide rail one (43), expansion slide rail two (44), expansion slide rail three (45), and expansion slide rail four (46) are all equipped with slide rails of the same size. The thickness of the slide rails is less than the height of the support column (4111). The slide rails are serrated and have a certain angle with the vertical direction.

5. The laser welding bulging fixture for large-section thin-walled cavity battery casings for electric bicycles according to claim 1, characterized in that: The expansion slider (47) has serrated slide rail grooves (471) on all four sides. The slide rail grooves (471) also form a certain angle with the vertical direction. The slide rail and the slide rail grooves (471) are wedge-shaped. The expansion slider (47) has piston rod connection holes (472) and support column through holes (473) on the upper and lower surfaces.

6. The laser welding bulging fixture for large-section thin-walled cavity battery casings for electric bicycles according to claim 1, characterized in that: Bottom bonding blocks (481) are bolted to the four sides of the upper end of the bottom pad (48); the bottom bonding block (481), expansion slide rail one (43), expansion slide rail two (44), expansion slide rail three (45), expansion slide rail four (46) are all provided with chamfers above the bonding surface of the inner wall of the battery casing (51).

7. The laser welding bulging fixture for large-section thin-walled cavity battery casings for electric bicycles according to claim 1, characterized in that: The piston rod (42) of the expansion cylinder (41) has a connecting threaded hole (421) at the top.

8. The laser welding bulging fixture for large-section thin-walled cavity battery casings for electric bicycles according to claim 1, characterized in that: The tabletop (12) is provided with several air pipe through holes (121), bolt through holes and piston rod through holes above it.

9. The laser welding bulging fixture for large-section thin-walled cavity battery casings for electric bicycles according to claim 1, characterized in that: The battery casing (5) includes a battery casing (51) and a battery casing base plate (52). The battery casing base plate (52) is stamped and formed with steps on its edges, which facilitates better airtightness after laser welding with the battery casing (51).

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