Method for processing long lithium battery aluminum shell

Abstract

The application discloses a method for processing a special long lithium battery aluminum shell, which comprises the following steps: (1) preparing an aluminum square tube blank by hot extrusion; (2) processing two edge frame rods A and B by fine grinding, connecting the four edge frame rods by springs to form a rectangular outer frame with eight inclined surfaces and smaller length and width than the aluminum square tube; (3) processing an inner mold by milling first and then fine grinding; (4) placing the rectangular outer frame on a workbench, slidably connecting the edge frame rods A and B with the workbench, placing the inner mold above the rectangular outer frame, using a hydraulic machine and connecting a piston rod of the hydraulic machine with the inner mold; (5) sleeving the aluminum square tube blank outside the rectangular outer frame, driving the piston rod of the hydraulic machine to go down, pulling the inner mold to slide downward along the eight inclined surfaces of the rectangular outer frame, and gradually expanding the rectangular outer frame outward. The application can conveniently process the special long lithium battery aluminum shell and has low processing cost.

Description

Technical Field

[0001] This invention relates to the field of lithium battery motor casing processing technology, and specifically to a method for processing extra-long lithium battery aluminum casings. Background Technology

[0002] Traditional lithium battery aluminum casings have always been a major challenge in aluminum material processing due to three major difficulties: thin walls, extremely tight dimensional tolerances, and extremely tight form and position tolerances. Therefore, the traditional processing method for lithium battery aluminum casings mostly involves extruding a tube blank, followed by several cold drawing and annealing processes, and then several more cold drawing processes. However, this extrusion, cold drawing, annealing, and further cold drawing process results in a very low yield due to the large number of processing steps, and the final step requires cleaning to remove oil contaminants to meet the requirements of the finished product. This processing method makes it difficult to reduce processing costs.

[0003] In the existing technology, some people have invented a method to manufacture aluminum casings using cold forming. However, this cold forming method can only be used to manufacture lithium battery aluminum casings with a length of less than 600 mm. This is because the mold for cold forming is made by wire cutting. However, no matter what wire cutting method is used, the effective height of the wire cutting cannot exceed 600 mm. Once it exceeds 600 mm, the wire used for wire cutting will shake more violently, which will cause the deviation of the cutting surface to increase sharply, and the cold-working mold produced cannot achieve the tolerance accuracy.

[0004] Therefore, there is an urgent need to invent a method for processing extra-long aluminum casings for lithium batteries that has low processing costs. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides a method for processing extra-long aluminum casings for lithium batteries.

[0006] The technical solution adopted in this invention is:

[0007] A method for processing extra-long aluminum casings for lithium batteries includes the following steps:

[0008] (1) Use hot extrusion to produce aluminum square tube blanks and cut them into a set length;

[0009] (2) Using a precision grinding process, process two frame rods A and two frame rods B. Frame rods A and B have the same structure but are symmetrical. The upper ends of the two adjacent outer sides of frame rods A and B are set as bevels. Frame connecting holes are set at the bottom of frame rods A and B. Use springs to connect the two frame rods A and B circumferentially to form a rectangular outer frame with eight bevels and a length and width smaller than the length and width of the inner hole of the aluminum square tube blank, respectively.

[0010] (3) A cross-shaped inner mold is machined by milling and then fine grinding. The inner mold has eight inner surfaces that slide with the eight outer surfaces of the four rectangular frame rods respectively. The bottom of the inner mold has an inner mold connection hole.

[0011] (4) Place the eight inclined surfaces of the rectangular outer frame vertically upward on a workbench with a central hole and four circular through holes. Connect the two side frame rods A and the two side frame rods B to the workbench radially and slidably through the four screws passing through the circular through holes. Place the inner mold on top of the rectangular outer frame and make the lower ends of the eight inner sides of the inner mold contact the upper ends of the eight inclined surfaces of the rectangular outer frame. Use a hydraulic press to connect the piston rod of the hydraulic press vertically upward to a connecting rod passing through the central hole of the workbench. The upper end of the connecting rod passes through the rectangular outer frame and connects to the inner mold mounting hole.

[0012] (5) Place the pre-cut aluminum square tube blank on the outside of the rectangular outer frame, drive the piston rod of the hydraulic press down, pull the inner mold down along the eight inclined surfaces of the rectangular outer frame, and gradually push the rectangular outer frame outward; when the inner mold passes through the eight inclined surfaces, the aluminum square tube blank will be pushed into the dimensional tolerance range of the lithium battery aluminum shell.

[0013] (6) After the inner mold continues to descend a certain distance, stop the piston rod from descending and then drive the piston rod of the hydraulic press to ascend, so that the inner mold exits the rectangular outer frame;

[0014] (7) Take out the finished aluminum shell and check the dimensional deviation.

[0015] Furthermore, the intersecting outer angle A of the two outer surfaces of frame rods A and B without bevels is set as a rounded corner, and the size and precision of the rounded corner are equal to the size and precision of the rounded corner of the inner hole of the aluminum shell. This improves the processing precision of the aluminum shell.

[0016] Furthermore, the eight inner surfaces of the inner mold form four intersecting interior angles, and each of the four intersecting interior angles has an arc groove at its corner to accommodate the intersecting exterior angle B formed by the two outer surfaces of the inclined surfaces of the frame rods A and B. This allows the intersecting exterior angle B of the frame rods A and B to be accommodated in the arc groove of the inner mold when the piston rod pulls the inner mold down along the eight inclined surfaces of the rectangular outer frame, thereby increasing the contact area between the rectangular frame and the inner mold and improving processing accuracy.

[0017] Furthermore, the bottom of each of the eight inclined surfaces of the inner mold contacting the rectangular frame rod is set with rounded corners. This reduces sliding resistance and ensures machining accuracy when the piston rod pulls the inner mold down along the eight inclined surfaces of the rectangular outer frame.

[0018] Furthermore, the slope of the inclined surfaces of both frame rod A and frame rod B is 4–6°, and the height is 8–12 mm. The control piston rod pulls the inner mold along the eight inclined surfaces of the rectangular outer frame for a suitable distance.

[0019] Furthermore, both frame rods A and B have beveled outer surfaces, each with several spring holes along its height. These spring holes are used to install springs, improving the connection stability between the springs and the rectangular frame rods.

[0020] Furthermore, the springs are helical springs of two different lengths, with each helical spring having its two ends placed in corresponding spring holes and connected to frame rod A and frame rod B respectively by adhesive bonding. This improves the stability of the rectangular outer frame and enhances processing accuracy.

[0021] Furthermore, the cross-sectional dimensions of the aluminum square tube blank are: the length is 0.4 to 0.5 mm smaller than the length of the finished aluminum shell, and the width is 0.4 to 0.5 mm smaller than the width of the finished aluminum shell.

[0022] Furthermore, the length of the rectangular outer frame is 1.5 to 2 mm smaller than the length of the cross-section of the aluminum square tube blank, and the width is 1.5 to 2 mm smaller than the width of the cross-section of the aluminum square tube blank.

[0023] Furthermore, the length and width deviations of the cross sections of frame rods A and B without bevels are both ±0.02mm, and the thickness deviations of the contact portions between the inner mold and frame rods A and B are both -0.05 to +0.02mm.

[0024] The beneficial effects of this invention are as follows: This invention uses hot extrusion to produce aluminum square tube blanks, and then uses an inner mold that slides within a rectangular outer frame composed of frame rods A, B, and springs to cold-stretch the hot-extruded aluminum square tube blanks to the specified dimensions of a lithium battery aluminum casing using existing hydraulic press equipment. Since the cold-stretching mold of this invention consists of an inner mold and a rectangular outer frame, and the inner mold and the rectangular frame rods forming the rectangular outer frame can be machined by milling and precision grinding, any length can be processed as needed while ensuring high processing accuracy. Therefore, the method of this invention can conveniently process extra-long lithium battery aluminum casings at a low processing cost. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the cross-sectional structure of the aluminum square tube blank prepared in Embodiment 1 of the present invention.

[0026] Figure 2 This is a schematic diagram of the structure of the frame rod A processed according to Embodiment 1 of the present invention.

[0027] Figure 3 yes Figure 2 Top view.

[0028] Figure 4 yes Figure 2 Side view.

[0029] Figure 5 This is a schematic diagram of the structure of the frame rod B processed in Embodiment 1 of the present invention.

[0030] Figure 6 yes Figure 5 Top view.

[0031] Figure 7 yes Figure 5 Side view.

[0032] Figure 8 This is a schematic diagram of the rectangular outer frame manufactured according to Embodiment 1 of the present invention.

[0033] Figure 9 This is a schematic diagram of the structure of the inner mold processed in Embodiment 1 of the present invention.

[0034] Figure 10 yes Figure 9 Side view.

[0035] Figure 11 This is a schematic diagram illustrating the working principle of the inner mold and rectangular outer frame of the present invention. Detailed Implementation

[0036] The present invention will be further illustrated below with specific examples to facilitate understanding of the invention, but this does not limit the invention.

[0037] Example 1

[0038] This embodiment provides a method for processing extra-long aluminum casings for lithium batteries, including the following steps:

[0039] The first step is to produce aluminum square tube blanks using hot extrusion; for example... Figure 1 As shown, the cross-sectional length of the aluminum square tube blank 1 prepared in this embodiment is 93.9±0.3mm, the width is 51.5±0.3mm, and the thickness is (0.5-0.06)~(0.5+0.08)mm. Due to the relatively large tolerance range, there are no difficulties in the production process.

[0040] The second step involves using a precision grinding process to machine the four frame bars: two frame bars A11 and two frame bars B12. (See reference...) Figures 2-7Both frame rods A11 and B12 are cuboids with a length of 1200mm and a cross-sectional length of 30±0.02mm and a width of 15±0.02mm. When the cuboids are placed vertically along their length, each cuboid has a 10mm deep M16 threaded hole at its bottom center, which serves as the frame connection hole. The four sides of the cuboids are designated as first side 113, second side 114, third side 117, and fourth side 116. First side 113 is opposite to third side 117, and second side 114 is opposite to fourth side 116. The upper ends of third side 117 and fourth side 116 are respectively provided with a first inclined surface 111 and a second inclined surface 112. The height of both the first inclined surface 111 and the second inclined surface 112 is 10mm, and both are inclined at 5° towards the top surface 115. The first side 113 and the second side 114 are connected by an arc surface with a radius of 1.2 mm. The third side 117 and the fourth side 116 are connected by a chamfered surface with a radius of 1.25 x 45°. Three Φ5 mm spring holes A1171 are evenly distributed along the length of the third side 117 of the cuboid, and three Φ5 mm spring holes B1161 are evenly distributed along the length of the fourth side 116 of the cuboid. The frame rod B12 and the frame rod A11 are axially symmetrical; their specific structure will not be described in detail.

[0041] The third step is to make a helical spring with an outer diameter of φ5 using a steel wire with a diameter of 1mm. (See attached document.) Figure 8 According to the final dimensions, two lengths of helical springs, helical spring A31 and helical spring B32, are manufactured. Two side frame rods A11 and two side frame rods B12 are placed diagonally to form a rectangle, with the sides containing the spring holes facing each other. Then, the two lengths of helical springs are used to connect the four corners of the rectangle's side frame rods A11 and B12 to form a rectangular outer frame 10. The external dimensions of the rectangular outer frame 10 are: height 1200mm, length 92.2±0.2mm, width 49.8±0.2mm, and all four corners of the rectangular outer frame 10 are rounded with a radius of R=1.2mm.

[0042] In practice, the two lengths of helical springs are inserted into the 24 spring holes of the frame rod A11 and the frame rod B12 respectively, and then glued in place.

[0043] The fourth step is to machine the inner mold 20 using a milling followed by finish grinding method. (See reference...) Figure 9 and Figure 10The inner mold 20 is made of a solid square steel with a length of 1000mm. First, the solid square steel is machined into a rectangle with a length of 73.5±0.3mm and a width of 36±0.3mm using a milling machine. Then, four right-angled notches with the same structure, each 15mm long and 7.5mm wide, are milled at the four corners of the rectangle. A circular arc groove 21 with an radius of 3 is milled at the inner corner of the four right-angled notches along the height direction. Then, the inner mold 20 is placed vertically along its length direction, and an M27*2 threaded hole, i.e., the inner mold connection hole, is opened at the center of its bottom. The eight right angles at the bottom of the four right-angled notches are rounded to a radius of 2. Finally, the inner mold 20 was precision ground using a grinding machine to create eight sides (C, D, E, F, G, H, I, J) with four right-angle notches, as well as two sides (A, B) in the width direction. The distance from side D to side E is also the distance from side I to side H, which is equal to (33.5-0.05)~(33.5+0.02) mm; the distance from side C to side J is also the distance from side F to side G, which is equal to (21-0.05)~(21+0.02) mm; and the distance from side A to side B is equal to 36±0.02 mm.

[0044] Step 5, refer to Figure 11 The rectangular outer frame 10 is placed vertically with its eight inclined surfaces facing upwards on a worktable 40 having a central hole and four circular through holes. Two side frame rods A11 and two side frame rods B12 are slidably connected to the worktable 40 via four screws passing through the circular through holes. An inner mold 20 is placed above the rectangular outer frame 10, with the lower ends of its eight inner surfaces contacting the upper ends of the eight inclined surfaces of the rectangular outer frame 20. A hydraulic press 50 is used, with its piston rod 51 vertically upwards connected to a connecting rod 60 passing through the central hole of the worktable. The upper end of the connecting rod 60 passes through the rectangular outer frame 10 and connects to the inner mold mounting hole. The diameters of the four circular through holes in the worktable 40 are sufficient to accommodate the movement distances of the side frame rods A11 and B12.

[0045] Step 6: After removing the burrs from the pre-cut aluminum square tube blank 1, fit it onto the outside of the rectangular outer frame 10. Drive the piston rod of the hydraulic press 50 downwards, pulling the inner mold 20 down along the eight inclined surfaces of the rectangular outer frame 10, gradually expanding the rectangular outer frame 10 outwards. After the inner mold 20 passes through the eight inclined surfaces, the aluminum square tube blank 1 is expanded to the dimensional tolerance range of the lithium battery aluminum shell. That is, the cross-sectional dimensions of the inner hole of the lithium battery aluminum shell are (93.5-0.09)~(93.5+0.06)mm in length and (51-0.09)~(51+0.06)mm in width.

[0046] Step 7: When the inner mold 20 continues to descend to the center of the rectangular outer frame 10, stop the piston rod from descending and then drive the piston rod of the hydraulic press to rise, so that the inner mold 20 exits the rectangular outer frame 10.

[0047] (8) Take out the finished aluminum shell and check the dimensional deviation.

[0048] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also within the protection scope of the present invention.

Claims

1. A method for processing extra-long aluminum casings for lithium batteries, characterized in that, Includes the following steps: (1) Use hot extrusion to produce aluminum square tube blanks and cut them into a set length; (2) Using a precision grinding process, process two frame rods A and two frame rods B. Frame rods A and B have the same structure but are symmetrical. The upper ends of the two adjacent outer sides of frame rods A and B are set as bevels. Frame connecting holes are set at the bottom of frame rods A and B. Use springs to connect the two frame rods A and B circumferentially to form a rectangular outer frame with eight bevels and a length and width smaller than the length and width of the inner hole of the aluminum square tube blank, respectively. (3) A cross-shaped inner mold is machined by milling and then fine grinding. The inner mold has eight inner surfaces that slide with the eight outer surfaces of the four frame rods respectively. The bottom of the inner mold has an inner mold connection hole. (4) Place the eight inclined surfaces of the rectangular outer frame vertically upward on a workbench with a central hole and four circular through holes. Connect the two side frame rods A and the two side frame rods B to the workbench radially and slidably through the four screws passing through the circular through holes. Place the inner mold on top of the rectangular outer frame and make the lower ends of the eight inner sides of the inner mold contact the upper ends of the eight inclined surfaces of the rectangular outer frame. Use a hydraulic press to connect the piston rod of the hydraulic press vertically upward to a connecting rod passing through the central hole of the workbench. The upper end of the connecting rod passes through the rectangular outer frame and connects to the inner mold mounting hole. (5) Place the pre-cut aluminum square tube blank on the outside of the rectangular outer frame, drive the piston rod of the hydraulic press down, pull the inner mold down along the eight inclined surfaces of the rectangular outer frame, and gradually push the rectangular outer frame outward; when the inner mold passes through the eight inclined surfaces, the aluminum square tube blank will be pushed into the dimensional tolerance range of the lithium battery aluminum shell. (6) After the inner mold continues to descend a certain distance, stop the piston rod from descending and then drive the piston rod of the hydraulic press to ascend, so that the inner mold exits the rectangular outer frame; (7) Take out the finished aluminum shell and check the dimensional deviation.

2. The method for processing extra-long aluminum casings for lithium batteries according to claim 1, characterized in that, The intersecting outer angle A of the two outer surfaces of frame rod A and frame rod B without bevels is set as a rounded corner, and the size and precision of the rounded corner are equal to the size and precision of the rounded corner of the inner hole of the aluminum shell.

3. The method for processing extra-long aluminum casings for lithium batteries according to claim 1, characterized in that, The eight inner surfaces of the inner mold form four intersecting inner angles. Each of the four intersecting inner angles has a rounded groove at its corner. The rounded groove is used to accommodate the intersecting outer angle B formed by the two outer surfaces of the inclined surfaces of the frame rod A and the frame rod B.

4. The method for processing extra-long aluminum casings for lithium batteries according to claim 1, characterized in that, The bottom of all eight inclined surfaces of the inner mold contact rectangular frame rod are set with rounded corners.

5. The method for processing extra-long aluminum casings for lithium batteries according to claim 1, characterized in that, The slope of the beveled surfaces of both frame rod A and frame rod B is 4 to 6 degrees, and the height is 8 to 12 mm.

6. The method for processing extra-long aluminum casings for lithium batteries according to claim 1, characterized in that, Both frame rod A and frame rod B have beveled outer surfaces, and each has several spring holes in its height direction.

7. The method for processing extra-long aluminum casings for lithium batteries according to claim 6, characterized in that, The springs are helical springs of two lengths. The two ends of each helical spring are placed in two corresponding spring holes and connected to the frame rod A and the frame rod B by adhesive.

8. The method for processing extra-long aluminum casings for lithium batteries according to claim 1, characterized in that, The cross-sectional dimensions of the aluminum square tube blank are: the length is 0.4 to 0.5 mm smaller than the length of the finished aluminum shell, and the width is 0.4 to 0.5 mm smaller than the width of the finished aluminum shell.

9. The method for processing extra-long aluminum casings for lithium batteries according to claim 1, characterized in that, The length of the rectangular outer frame cross-section is 1.5 to 2 mm smaller than the length of the cross-section of the aluminum square tube blank, and the width is 1.5 to 2 mm smaller than the width of the cross-section of the aluminum square tube blank.

10. A method for processing extra-long aluminum casings for lithium batteries according to claim 1, characterized in that, The length and width deviations of the cross sections of frame rods A and B without bevels are both ±0.02mm, and the thickness deviations of the contact portions between the inner mold and frame rods A and B are both -0.05 to +0.02mm.

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