Cylindrical battery steel shell rolling groove and hob cutter mold thereof

Abstract

This invention discloses a cylindrical battery steel shell grooving groove and its roller cutter mold. The groove opening is asymmetrical, with the upper part consisting of two arc segments and the lower part consisting of a straight line segment with a certain angle. The corresponding roller cutter mold adopts a semi-heart-shaped small protrusion design. The semi-heart-shaped small protrusion is generally composed of arcs with rounded radii of R3 and R4, a straight line segment with an angle of θ2, and an arc with a rounded radius of R5. The connection between the semi-heart-shaped small protrusion and the large protrusion adopts an arc plus a straight line form. The upper part is composed of arcs with rounded radii of R6 and R7 and an inward concave angle composed of two straight line segments, which are a straight line segment with an angle of θ1 and a horizontal straight line segment, respectively. The lower part is composed of an arc with a rounded radius of R8 and an inward concave angle composed of two straight line segments, which are a straight line segment with an angle of θ3 and a horizontal straight line segment, respectively.

Description

Technical Field

[0001] This invention relates to a cylindrical battery steel shell grooving die and a grooving tool that can reduce chipping during the grooving process and the risk of bulging in subsequent packaging processes. Background Technology

[0002] Cylindrical battery steel casings are cylindrical packaging containers made from specialized battery casing materials through multiple deep drawing and thinning processes. They are primarily used for encapsulating various types of alkaline and lithium-ion batteries. The battery encapsulation process involves two key forming steps: grooving and sealing. Grooving is used to create an inward groove on the straight wall of the cylindrical steel casing using a roller die, primarily the convex part of the roller cutter. This groove supports the cap during encapsulation and facilitates subsequent sealing and edge curling.

[0003] Currently, most grooving methods use semi-circular roller cutter protrusions, resulting in grooves that are roughly semi-circular in shape. This grooving method has two main drawbacks. First, it can easily cause "bulging" of the lower part of the groove during sealing and edge rolling. This means that the lower part of the groove bulges outward under axial pressure during sealing and edge rolling, affecting the quality of the finished battery. Second, the friction between the roller cutter protrusion and the steel shell surface during grooving can easily cause chipping on the steel shell surface, which can significantly impact battery safety.

[0004] like Figure 1 As shown, the existing cylindrical steel shell grooving and hob die structure has a grooving groove 11 machined on the surface of the cylindrical steel shell 10, and a protruding hob head 21 is provided in the radial direction of the hob 20. The central axis 22 of the hob cutter disc is also shown in the figure. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a cylindrical battery steel shell grooving method that can significantly improve the bulging of the steel shell sealing edge and reduce the risk of chipping during grooving.

[0006] The technical problem it aims to solve can be addressed through the following technical solutions.

[0007] A groove is formed on the cylindrical surface of a cylindrical battery steel casing. The groove's cross-sectional profile, passing through the vertical centerline of the cylinder, comprises successively and naturally connected initial arc segments with a fillet radius of R0, first arc segments with a fillet radius of R1, initial straight line segments with an inclination angle of θ0, and second arc segments with a fillet radius of R2.

[0008] R0 > R2 > R1;

[0009] The starting end of the initial arc segment is tangent to the generatrix of the cylinder, and the ending end of the second arc segment is tangent to the generatrix of the cylinder; with the cylinder as a reference, the center of the initial arc segment is located at the inner end, the center of the first arc segment is located at the outer end, and the center of the second arc segment is located at the inner end; the two ends of the initial straight line segment are tangent to the first arc segment and the second arc segment, respectively.

[0010] Furthermore, let the outer diameter of the cylindrical steel shell be D, the groove depth be h1, and the inclination angle be θ0 = arctan(2*k1*h1 / D), where k1 = 5~6.

[0011] As a further improvement to this technical solution, the range of R0, R1 and R2 is 0.5 to 1.5 mm; h1 is 0.5 to 2 mm; and the vertical height h2 of the groove is 3 to 5 mm.

[0012] The technical solution of the present invention is also applicable to battery steel shells of other sizes. As a preferred embodiment of the present invention, when the steel shell is a No. 5 steel shell, D = 14.1 ± 0.2 mm; when the steel shell is an 18 series steel shell, D = 18 ± 0.5 mm; when the steel shell is a 21 series steel shell, D = 21 ± 0.5 mm.

[0013] Another technical problem to be solved by the present invention is to provide a hobbing die for forming the said groove.

[0014] The following technical solution is adopted:

[0015] A hobbing die for forming grooves in the aforementioned cylindrical battery steel casing includes a hobbing cutter disc. Its characteristic is that, in any cross-section passing through the vertical central axis of the cutter disc, the cutter head includes a large protrusion extending radially outward from the cutter disc body, and a small protrusion is provided at the end of the large protrusion radially.

[0016] The main body of the large protrusion runs in a straight radial direction;

[0017] The cross-sectional outline of the small protrusion includes, from top to bottom, a third arc segment with a fillet radius of R3, a fourth arc segment with a fillet radius of R4, a second straight line segment with an inclination angle of θ2, and a fifth arc segment with a fillet radius of R5, which are naturally connected in sequence. The initial end of the third arc segment is tangent to the horizontal line, and the two ends of the second straight line segment are tangent to the fourth and fifth arc segments, respectively. The terminating end of the fifth arc segment is tangent to the horizontal line.

[0018] In other cross-sectional contour lines, between the upper contour line of the straight section of the large convex head and the initial end of the third arc segment of the small convex head, from top to bottom, there are successively connected sixth arc segments with a fillet radius of R6, seventh arc segments with a fillet radius of R7, and a first straight line segment with an inclination angle of θ1; between the lower contour line of the straight section of the large convex head and the terminating end of the fifth arc segment of the small convex head, from top to bottom, there are successively connected third straight line segments with an inclination angle of θ3 and eighth arc segments with a fillet radius of R8; among which,

[0019] The initial end of the sixth arc segment and the terminating end of the eighth arc segment are tangent to the upper and lower contour lines of the straight section of the large convex head, respectively; the sixth arc segment and the seventh arc segment are naturally connected, and the terminating end of the seventh arc segment is tangent to the first straight line segment; the starting end of the eighth arc segment is tangent to the third straight line segment.

[0020] Furthermore, θ1=10 to 15°, θ2=θ0-α, α=10 to 15°, θ3=θ0+β, and β=0 to 5°.

[0021] Furthermore, the sizes of R3, R4, R5, R7 and R8 are 0.2–0.4 mm, and R6 is 0.5–0.7 mm.

[0022] As a further improvement to the hobbing die, the axial height of the straight section of the large convex head is h3, the radial width of the small convex head and its connection with the straight section of the large convex head is w2, the axial height of the small convex head is h4, the axial distance from the center of the fourth arc segment to the upper contour line of the straight section of the large convex head is h5, and the radial width from the farthest point of the fourth arc segment to the starting point of the third arc segment is w1.

[0023] h3=(1 / 3)*h2, w2=h4=(1 / 2)*h3, h5=(1 / 3)*h3, w1=(2 / 3)*w2.

[0024] The cylindrical battery steel shell grooving and its roller die provided by the above technical solution, with the lower part of the cylindrical battery steel shell groove being an asymmetrical grooving groove with a certain inclination angle and the corresponding roller die having a semi-heart-shaped small convex head, can significantly improve the bulging of the steel shell sealing edge and reduce the risk of chip shedding during grooving. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the existing cylindrical steel shell grooving and hobbing die.

[0026] Figure 2 This is a schematic diagram of the asymmetric groove opening of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of the hobbing die of the present invention;

[0028] In the diagram: 10 – Cylindrical steel shell; 11 – Groove opening; 20 – Hob cutter; 21 – Hob cutter protrusion; 22 – Central axis.

[0029] 100 – Cylindrical steel shell; 110, 111, 112 – Circular arc; 120 – Straight segment; 130 – Central axis; 140 – Groove.

[0030] 200 – Hob; 210 – Small convex head; 213, 214, 215, 216, 217, 218 – Circular arcs; 221, 222, 223 – Straight line segments; 230 – Large convex head; 231 – Upper contour line; 232 – Lower contour line

[0031] 230 - Large convex head Detailed Implementation

[0032] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] This invention provides an asymmetrical grooving groove with a certain inclination angle at the bottom and a corresponding hobbing die with a semi-heart-shaped small protrusion.

[0034] Reference Figure 2 The groove structure is as follows:

[0035] An annular groove 140 is formed on the cylindrical surface of the cylindrical steel shell 100. This groove is asymmetrical, with the upper part consisting of two naturally connected arcs 110 and 111, with fillet radii of R0 and R1 respectively. The lower part is a straight segment 120 with a certain angle of inclination θ0. The transition between this straight segment and the fillet of the shell body forms an arc 112 with a fillet radius of R2. Specifically, the initial segment of arc 110 is tangent to the generatrix of the cylinder of the steel shell 100, the two ends of the straight segment 120 are tangent to arcs 111 and 112 respectively, and the terminating end of arc 112 is also tangent to the generatrix of the cylinder of the steel shell 100. The central axis 130 of the cylinder is also shown in the figure.

[0036] The outer diameter of the steel shell is D, the groove depth is h1, and the total height of the grooved portion is h2. Wherein, R0 > R2 > R1, and R0, R1, R2 = (0.5~1.5) mm; the outer diameter D is determined by the cylindrical steel shell model. When it is a #5 steel shell, D = 14.1 ± 0.2 mm; when it is an 18 series steel shell, D = 18 ± 0.5 mm; when it is a 21 series steel shell, D = 21 ± 0.5 mm; h1 = 0.5~2 mm; h2 = 3~5 mm; the inclination angle θ0 = arctan(2*k1*h1 / D), k1 = 5~6.

[0037] Reference Figure 3 The hobbing die structure of the present invention is a semi-heart-shaped small convex hobbing die, the specific structure of which is as follows:

[0038] In the radial direction of the hob head 200, there is a large protruding head 230, which includes a straight section and a small protruding head 210 protruding radially. The hob die adopts a semi-heart-shaped small protruding head design. The semi-heart-shaped small protruding head is generally composed of an arc 213 with a fillet radius of R3, an arc 214 with a fillet radius of R4, a straight line segment 222 with an inclination angle of θ2, and an arc 215 with a fillet radius of R5. The starting end of the arc 213 is tangent to the horizontal line, and the two ends of the straight line segment 222 are tangent to the arcs 214 and 215, respectively.

[0039] The connection between the semi-heart-shaped small convex head 210 and the straight section of the large convex head 230 adopts an arc plus straight line form. The upper part consists of an arc 216 with a rounded corner radius of R6, an arc 217 with a rounded corner radius of R7, and an inward concave angle composed of two straight line segments. The two straight line segments are a straight line segment 221 with an inclination angle of θ1 and a horizontal straight line segment (referring to the upper contour line 231 of the straight section of the large convex head). The lower part consists of an arc 218 with a rounded corner radius of R8 and an inward concave angle composed of two straight line segments. The two straight line segments are a straight line segment 223 with an inclination angle of θ3 and a horizontal straight line segment (referring to the lower contour line 232 of the straight section of the large convex head). The starting end of the arc 216 is tangent to the horizontal upper contour line 231, and the ending end of the arc 217 is tangent to the straight line segment 221. The two ends of the arc 218 are tangent to the horizontal lower contour line 232 and the straight line segment 223, respectively.

[0040] Among them, R3, R4, R5, R7, R8=(0.2~0.4)mm, R6=(0.5~0.7)mm, θ1=(10~15)°, θ2=θ0-α, α=10~15°, θ3=θ0+β, β=0~5°.

[0041] The height h3 of the straight section of the large convex head of the hob (that is, the distance between the upper and lower contour lines 231 and 232) is the same as the height h3 of the top and bottom surfaces. The depth w2 of the irregular end (including the small convex head and the part connecting it to the straight section of the large convex head) is the same as the depth w2 of the small convex head. The height h4 of the small convex head is the same as the distance h5 from the center of the small convex head (the center of arc 214) to the straight section of the large convex head. The radial distance w1 from the outermost end of arc 214 (radially) to the starting end of arc 213 is the same as the radial distance w1. Where h3 = (1 / 3) * h2, w2 = h4 = (1 / 2) * h3, h5 = (1 / 3) * h3, w1 = (2 / 3) * w2.

[0042] This grooving and hobbing die is suitable for grooving cylindrical steel shells such as #5, 18 series, and 21 series. The detailed dimensions of other sizes of steel shells may vary, but the main concept is the same.

[0043] The following will provide further explanation of the technical solutions described in this invention, in conjunction with specific embodiments.

[0044] Taking commonly used 18650, 5#, and 21700 steel shells as examples, the asymmetrical groove and semi-heart-shaped small convex humb hobs described in this invention were implemented on the basis of the original symmetrical groove and semi-circular hob, respectively. Evaluation showed that compared with the original symmetrical groove and semi-circular hob, the asymmetrical groove and semi-heart-shaped small convex humb hobs increased the axial load-bearing capacity (no bulging at the bottom of the groove) by 25%, 27%, and 22%, respectively, and reduced the forming force of the grooving hob by approximately 9%, 8%, and 12%, respectively. This significantly improved the sealing edge curling and bulging, while also reducing the risk of grooving chip shedding.

[0045] Table 1 below shows the comparative examples and relevant data for Example 1, which uses 18650 steel shells.

[0046] Table 2 below shows the comparative example and relevant data of Example 2 using No. 5 steel shell.

[0047] Table 3 below shows the relevant data for the comparative example and Example 1, which uses 18650 steel shells.

[0048] Table 1: (Unit: mm)

[0049]

[0050] Table 2: (Unit: mm)

[0051]

[0052] Table 3: (Unit: mm)

[0053]

[0054] Example 1: For a typical 18650 cylindrical steel shell, while keeping the groove depth and total height unchanged, the axial load capacity (no bulging at the bottom of the groove) is increased by 25% by optimizing the groove to an asymmetrical groove and using a semi-heart-shaped small convex hob, and the radial forming force of the grooving hob is reduced by about 9%, which helps to reduce the risk of bulging during packaging and chip shedding during grooving.

[0055] Example 2: For a typical #5 cylindrical steel shell, while keeping the groove depth and total height unchanged, the axial load capacity (no bulging at the bottom of the groove) is increased by 27% by optimizing the groove to an asymmetrical groove and using a semi-heart-shaped small convex hob, and the radial forming force of the grooving hob is reduced by about 8%, which helps to reduce the risk of bulging during packaging and chipping during grooving.

[0056] Example 3: For a typical 21700 cylindrical steel shell, while keeping the groove depth and total height unchanged, the axial load capacity (no bulging at the bottom of the groove) is increased by 22% by optimizing the groove to an asymmetrical groove and using a semi-heart-shaped small convex hob, and the radial forming force of the grooving hob is reduced by about 12%, which helps to reduce the risk of bulging during packaging and chip shedding during grooving.

Claims

1. A groove for a cylindrical battery steel casing, wherein a groove is formed on the cylindrical surface of the cylindrical battery steel casing, characterized in that, The arbitrary cross-sectional profile of the slot passing through the vertical centerline of the cylinder includes, in sequence, naturally contiguous initial arc segments with a fillet radius of R0, first arc segments with a fillet radius of R1, initial straight line segments with an inclination angle of θ0, and second arc segments with a fillet radius of R2; wherein... R0 > R2 > R1; The starting end of the initial arc segment is tangent to the generatrix of the cylinder, and the ending end of the second arc segment is tangent to the generatrix of the cylinder; with the cylinder as a reference, the center of the initial arc segment is located at the inner end, the center of the first arc segment is located at the outer end, and the center of the second arc segment is located at the inner end; the two ends of the initial straight line segment are tangent to the first arc segment and the second arc segment, respectively.

2. The cylindrical battery steel shell groove according to claim 1, characterized in that, Let the outer diameter of the cylindrical steel shell be D, the groove depth be h1, and the inclination angle be θ0 = arctan(2*k1*h1 / D), where k1 = 5~6.

3. The cylindrical battery steel shell groove according to claim 2, characterized in that, The range of R0, R1 and R2 is 0.5 to 1.5 mm; h1 is 0.5 to 2 mm; and the vertical height of the groove h2 is 3 to 5 mm.

4. The cylindrical battery steel casing groove according to claim 2, characterized in that, When the steel shell is No. 5 steel, D = 14.1 ± 0.2 mm; when the steel shell is No. 18 series steel, D = 18 ± 0.5 mm; when the steel shell is No. 21 series steel, D = 21 ± 0.5 mm.

5. A hobbing die for forming the groove of a cylindrical battery steel shell as described in any one of claims 1-4, comprising a hobbing cutter disc, characterized in that, In any cross-section passing through the vertical central axis of the cutter head, the cutter head includes a large convex head that protrudes radially from the cutter head body, and a small convex head protruding radially from the end of the large convex head, wherein... The main body of the large protrusion runs in a straight radial direction; The cross-sectional outline of the small protrusion includes, from top to bottom, a third arc segment with a fillet radius of R3, a fourth arc segment with a fillet radius of R4, a second straight line segment with an inclination angle of θ2, and a fifth arc segment with a fillet radius of R5, which are naturally connected in sequence. The initial end of the third arc segment is tangent to the horizontal line, and the two ends of the second straight line segment are tangent to the fourth and fifth arc segments, respectively. The terminating end of the fifth arc segment is tangent to the horizontal line. In other cross-sectional contour lines, between the upper contour line of the straight section of the large convex head and the initial end of the third arc segment of the small convex head, from top to bottom, there are successively connected sixth arc segments with a fillet radius of R6, seventh arc segments with a fillet radius of R7, and a first straight line segment with an inclination angle of θ1; between the lower contour line of the straight section of the large convex head and the terminating end of the fifth arc segment of the small convex head, from top to bottom, there are successively connected third straight line segments with an inclination angle of θ3 and eighth arc segments with a fillet radius of R8; among which, The initial end of the sixth arc segment and the terminating end of the eighth arc segment are tangent to the upper and lower contour lines of the straight section of the large convex head, respectively; the sixth arc segment and the seventh arc segment are naturally connected, and the terminating end of the seventh arc segment is tangent to the first straight line segment; the starting end of the eighth arc segment is tangent to the third straight line segment.

6. The hobbing die according to claim 5, characterized in that, θ1=10~15°, θ2=θ0-α, α=10~15°, θ3=θ0+β, β=0~5°.

7. The hobbing die according to claim 5, characterized in that, The sizes of R3, R4, R5, R7 and R8 are 0.2 to 0.4 mm, and R6 is 0.5 to 0.7 mm.

8. The hobbing die according to claim 5, characterized in that, Let h3 be the axial height of the straight section of the large convex head, w2 be the radial width of the small convex head and its connection with the straight section of the large convex head, h4 be the axial height of the small convex head, h5 be the axial distance from the center of the fourth arc segment to the upper contour line of the straight section of the large convex head, w1 be the radial width from the farthest point of the fourth arc segment to the starting point of the third arc segment, and h2 be the vertical height of the groove. h3=(1 / 3)*h2, w2=h4=(1 / 2)*h3, h5=(1 / 3)*h3, w1=(2 / 3)*w2.

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