Pressing rivet nut and fastening structure for soft metal plate

Abstract

The invention provides a pressing rivet nut and a fastening structure for a soft metal plate. The pressing rivet nut comprises a flange part and a pressing rivet part, wherein the flange part is provided with a discharging face suitable for abutting against a plate; the anti-torsion teeth are arranged on the discharging face and spaced from one another, any anti-torsion tooth extends outwards from the outer wall face of the pressing rivet nut in the radial direction of the pressing rivet nut, any anti-torsion tooth comprises a first end located on the outer side in the radial direction, and the distance L between any first end and the center line of the pressing rivet nut and the nominal diameter D of the pressing rivet nut meet the condition that L is larger than or equal to 3 / 2D. According to the technical scheme, the problem that in the prior art, when a pressing rivet nut is applied to a soft metal plate, the effect is poor is solved.

Description

Technical Field

[0001] The invention relates to the field of fasteners, and in particular provides a rivet nut and a fastening structure for soft metal plates. Background Art

[0002] Compression rivet nuts, also known as rivet nuts and self-fastening nuts, are a type of nut used on thin plates or sheet metals. They are round in shape and have embossed teeth and guide grooves on one end. The principle is that the embossed teeth are pressed into the preset holes of the sheet metal. Generally speaking, the aperture of the preset hole is slightly smaller than the embossed teeth of the rivet nut. The pressure causes the teeth of the rivet nut to squeeze into the plate, causing plastic deformation around the preset hole, and the deformed object is squeezed into the guide groove, thereby producing a locking effect.

[0003] When the rivet nut in the prior art is applied to a soft metal plate, it is easy to embed into the plate. Since the soft metal plate has good ductility, the torsion resistance of the rivet nut in the prior art is difficult to exert, resulting in the phenomenon of slipping teeth, etc.

[0004] Therefore, this field needs a new technical solution to solve the above problems. Summary of the invention

[0005] In order to solve the problem that the existing self-clinching nut has poor effect when applied to soft metal plates, the present invention provides a self-clinching nut for soft metal plates. The self-clinching nut of the present invention comprises: a flange portion, the flange portion having a discharge surface suitable for abutting against the plate; and a plurality of anti-torsion teeth, the anti-torsion teeth are arranged on the discharge surface and spaced apart from each other, any of the anti-torsion teeth extends outward from the outer wall surface of the self-clinching nut along the radial direction of the self-clinching nut, any of the anti-torsion teeth comprises a first end portion located on the radial outer side, and the distance L of any of the first end portions relative to the center line of the self-clinching nut and the nominal diameter D of the self-clinching nut satisfy: L≥3 / 2D.

[0006] The self-clinching nut of the present invention adopts a flange portion with a discharge surface to abut against a soft metal sheet, and an anti-torsion tooth is provided on the discharge surface to prevent the self-clinching nut from slipping. Specifically, the anti-torsion teeth are configured to be a plurality of mutually spaced apart, so that after the anti-torsion teeth are embedded in the sheet, the sheet that has not been deformed between the adjacent anti-torsion teeth provides a resistance torque opposite to the tightening torque for the anti-torsion teeth of the nut, thereby preventing the self-clinching nut from slipping. Any anti-torsion tooth extends radially outward from the outer wall surface of the self-clinching nut, so that the actual length of the anti-torsion tooth is the effective length, thereby minimizing the manufacturing cost. The distance L of the first end relative to the center line of the self-clinching nut and the nominal diameter D of the self-clinching nut satisfy L≥3 / 2D, on the one hand, ensuring that the anti-torsion tooth has sufficient effective length for anti-torsion, and on the other hand, ensuring that the outer diameter of the discharge surface provided with the anti-torsion tooth is flush with or exceeds the first end, reducing the pressure on the contact surface between the self-clinching nut and the sheet during installation, and preventing the self-clinching nut from excessively embedding into the soft metal sheet and causing the loss of sheet strength.

[0007] In the preferred technical solution of the above-mentioned self-clinching nut, the height h of any anti-torsion tooth relative to the discharge surface increases gradually from the inside to the outside along the radial direction. The anti-torsion tooth has a stronger anti-torsion effect as it is farther away from the center line of the self-clinching nut. Through the above-mentioned arrangement, part of the material of the anti-torsion tooth is omitted, and the manufacturing cost is reduced as much as possible while ensuring the anti-torsion effect.

[0008] In the preferred technical solution of the above-mentioned self-clinching nut, the width w of any of the anti-torsion teeth increases gradually from the inside to the outside along the radial direction, and the ratio of the height h to the width w satisfies: h / w≥0.9. Through the above-mentioned setting, the anti-torsion ability of the self-clinching nut on the soft plate is much higher than that of the ordinary self-clinching nut, and the mold clamping pressure for installing the self-clinching nut on the plate can be reduced, thereby improving the installation efficiency.

[0009] In the preferred technical solution of the above-mentioned self-clinching nut, the discharge surface is configured as a rotating surface and its center line coincides with the center line of the self-clinching nut, and the discharge surface is tilted away from the center line of the self-clinching nut. When the self-clinching nut is installed, the pressure generated by the upper and lower molds arranged on both sides of the plate usually presses the self-clinching nut into the corresponding mounting hole on the plate. However, the force is concentrated on the edge of the mounting hole, and the coating on the plate on the non-installation side is easily damaged due to the large stress. Through the above-mentioned setting, the discharge surface of the self-clinching nut of the present application is tilted away from the center line of the self-clinching nut, and the good ductility of the soft metal plate is used to guide the plate on the installation side to flow, reduce the force on the edge of the mounting hole of the plate, thereby protecting the coating on the non-installation side and minimizing the impact of the self-clinching nut on the plate.

[0010] In the preferred technical solution of the above-mentioned self-clinching nut, the self-clinching nut further includes a material receiving groove for receiving the material flowing due to deformation on the metal plate, and the material receiving groove is formed on the outer wall of the self-clinching nut and is located on the side of the flange portion where the anti-torsion teeth are provided. Through the above-mentioned arrangement, when the discharge surface, the anti-torsion teeth and the outer wall of the self-clinching nut squeeze the plate, the plate can flow into the material receiving groove, so that the self-clinching nut and the plate are riveted.

[0011] In the preferred technical solution of the above-mentioned rivet nut, the material receiving groove includes a bottom surface inclined toward the flange portion, and the bottom surface is connected to the discharge surface; the bottom surface is provided with a plurality of reinforcing ribs extending in the direction of the center line of the rivet nut, and any of the reinforcing ribs is connected to the corresponding anti-torsion tooth. Through the above-mentioned arrangement, the bottom surface of the material receiving groove is connected to the discharge surface, which is convenient for balancing the deformed portion of the plate flowing into the material receiving groove, preventing the deformable soft metal from squeezing the outer wall of the rivet nut (specifically, squeezing the thinner wall thickness on the outer wall due to the opening of the material receiving groove), and avoiding deformation or even failure of the threaded hole of the rivet nut. The reinforcing ribs connected to the anti-torsion teeth are arranged on the bottom surface to further ensure the strength of the bottom surface of the material receiving groove, and prevent the soft metal flowing into the material receiving groove from being squeezed and deformed, thereby affecting the function of the threaded hole.

[0012] In the preferred technical solution of the above-mentioned self-clinching nut, the self-clinching nut also includes a threaded hole, and the depth D of the threaded hole is p Satisfy D p ≥0.8D. Through the above arrangement, the self-clinching nut of the present invention can be adapted to high-strength bolts.

[0013] In order to solve the problem that the rivet nut in the prior art has a poor effect when applied to a soft metal sheet, the present invention also provides a fastening structure. The fastening structure of the present invention comprises: a soft metal sheet, the soft metal sheet comprises a mounting hole; and a rivet nut, at least part of which is accommodated in the mounting hole and comprises: a flange portion, the flange portion having a discharge surface against the soft metal sheet; and a plurality of anti-torsion teeth, the anti-torsion teeth are arranged on the discharge surface and spaced apart from each other, any of the anti-torsion teeth extends radially outward from the outer wall surface of the rivet nut, and the anti-torsion teeth comprise a first end portion located radially outward, and the distance L of the first end portion relative to the center line of the rivet nut and the nominal diameter D of the rivet nut satisfy: L≥3 / 2D. Through the above arrangement, the rivet nut in the fastening structure of the present invention is not easy to slip. Any anti-torsion tooth extends radially outward from the outer wall surface of the rivet nut, so that the actual length of the anti-torsion tooth is the effective length, thereby reducing the manufacturing cost to the greatest extent. The distance L of the first end relative to the center line of the rivet nut and the nominal diameter D of the rivet nut satisfy L≥3 / 2D. On the one hand, it ensures that the anti-torsion tooth has sufficient effective length for anti-torsion, and on the other hand, it ensures that the outer diameter of the discharge surface provided with the anti-torsion tooth is flush with or exceeds the first end, thereby reducing the pressure on the contact surface between the rivet nut and the plate during installation, and preventing the rivet nut from being excessively embedded in the soft metal plate, resulting in loss of plate strength.

[0014] In the preferred technical solution of the above-mentioned fastening structure, the height h1 of the first end relative to the discharge surface is in a predetermined ratio with the thickness of the soft metal sheet. Through the above-mentioned setting, when the height of the first end is in a predetermined ratio with the thickness of the sheet, the first end will not excessively weaken the strength of the sheet after being embedded in the sheet, while providing a higher torsional resistance for the rivet nut.

[0015] In the preferred technical solution of the above-mentioned fastening structure, the soft metal sheet is made of pure aluminum or pure copper. Through the above-mentioned configuration, the fastening structure of the present invention can be applied to pure aluminum or pure copper sheets with good sheet ductility, while ensuring that the rivet nut will not slip or over-embed on the soft metal sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings, in which: Figure 1 It is a structural schematic diagram of an embodiment of a self-clinching nut for soft metal sheet material of the present invention; Figure 2 It is a front view of an embodiment of a rivet nut for soft metal sheet according to the present invention; Figure 3 yes Figure 2 A cross-sectional view of an embodiment of a self-clinching nut for soft metal sheet material; Figure 4 is a bottom view of an embodiment of a rivet nut for a soft metal sheet according to the present invention; Figure 5 is a cross-sectional view of an embodiment of the fastening structure of the present invention.

[0017] List of reference numerals: 100, self-clinching nut; 10, nut body; 11, threaded hole; 12, outer wall surface; 20, flange portion; 21, discharge surface; 30, anti-torsion tooth; 31, first end portion; 32, second end portion; 40, material storage groove; 41, bottom surface; 42, reinforcing rib; 500, fastening structure; 501, soft metal sheet; 502, mounting hole. DETAILED DESCRIPTION

[0018] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0019] It should be noted that, in the description of the present invention, the terms “first” and “second” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0020] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, an indirect connection through an intermediate medium, or the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] In order to solve the problem that the rivet nut in the prior art has a poor effect when applied to soft metal sheets, the present invention provides a rivet nut 100 for soft metal sheets. The rivet nut 100 of the present invention includes: a flange portion 20, the flange portion 20 has a discharge surface 21 suitable for abutting against the sheet; and a plurality of anti-torsion teeth 30, the anti-torsion teeth 30 are arranged on the discharge surface 21 and are spaced apart from each other, any anti-torsion tooth 30 extends radially outward from the outer wall surface 12 of the rivet nut 100, any anti-torsion tooth 30 includes a first end portion 31 located radially outward, and the distance L of any first end portion 31 relative to the center line of the rivet nut 100 and the nominal diameter D of the rivet nut 100 satisfy: L≥3 / 2D.

[0022] Figure 1 It is a structural schematic diagram of an embodiment of a self-clinching nut for soft metal sheet material of the present invention; Figure 2 It is a front view of an embodiment of a rivet nut for soft metal sheet according to the present invention; Figure 3 yes Figure 2 A cross-sectional view of an embodiment of a self-clinching nut for soft metal sheet material; Figure 4 FIG. 2 is a bottom view of an embodiment of a rivet nut for a soft metal sheet according to the present invention. Figures 1 to 4 As shown, in one or more embodiments, the self-clinching nut 100 for a soft metal sheet material of the present invention includes a nut body 10 and a flange portion 20 formed on the nut body 10 .

[0023] In one or more embodiments, the nut body 10 extends in a predetermined direction and has a center line C, and is configured to be roughly cylindrical. Alternatively, the nut body 10 may also be configured into other suitable shapes according to actual needs. A threaded hole 11 is formed inside the nut body 10, so that after the self-clinching nut 100 is installed on the plate, the threaded hole 11 is used to cooperate with the bolt to fix the appropriate device to the plate. In one or more embodiments, the depth Dp of the threaded hole 11 satisfies that Dp is greater than or equal to 0.8D. Wherein, D is the nominal diameter of the threaded hole 11. Through the above configuration, the self-clinching nut 100 of the present invention can be adapted to high-strength bolts.

[0024] Continue reading Figure 1 and Figure 2 In one or more embodiments, the nut body 10 includes an outer wall surface 12, and the flange portion 20 is configured in a circular ring shape surrounding the outer wall surface 12. Alternatively, the flange portion 20 can also be configured in other suitable shapes according to actual needs.

[0025] In one or more embodiments, the outer diameter of the flange portion 20 is larger than the outer diameter of the outer wall surface 12 of the nut body 10. The flange portion 20 mainly bears the function of compressing the plate to deform it, thereby reducing the wall thickness of the nut body 10 as much as possible, thereby reducing the volume of the pressure rivet nut, saving raw materials and reducing weight. Alternatively, the side of the nut body 10 opposite to the discharge surface 21 (based on Figure 2 The side shown in the direction above the flange portion 20 is configured to be flush with the outer diameter of the flange portion 20 or larger than the outer diameter of the flange portion 20 to improve the strength of the flange portion 20.

[0026] based on Figure 2In the orientation shown, in one or more embodiments, the flange portion 20 has a discharge surface 21 that is inclined downward. The discharge surface 21 can be configured as a substantially conical rotation surface. With the center line of the rivet nut 100 as a reference, the discharge surface 21 is inclined away from the center line of the rivet nut 100 and the rotation center line of the discharge surface 21 coincides with the center line of the rivet nut 100. The discharge surface 21 is suitable for abutting against the plate, forcing the plate to deform and guiding the flow of material on the plate. In the prior art, the plane where the rivet nut 100 is set at the discharge surface 21 is usually a plane perpendicular to the center line. When the upper and lower dies for installing the rivet nut are closed to embed the rivet nut 100 into the mounting hole 502 on the plate, the force on the edge of the mounting hole 502 is relatively concentrated. The coating on the plate on the non-installation side is easily damaged due to the large stress. Through the above-mentioned arrangement, the discharge surface 21 of the rivet nut 100 of the present application is tilted away from the center line of the rivet nut 100, and the good ductility of the soft metal sheet 501 is utilized to guide the flow of the sheet on the installation side (the installation side and the non-installation side refer to the two opposite sides of the sheet, and the side where the flange portion 20 is located is the installation side), thereby reducing the force on the edge of the installation hole 502 of the sheet, thereby protecting the coating on the non-installation side and minimizing the impact of the rivet nut 100 on the sheet.

[0027] Continue reading Figure 2 and Figure 3 In one or more embodiments, the self-clinching nut 100 further includes anti-torsion teeth 30. The anti-torsion teeth 30 are arranged on the discharge surface 21 and are spaced apart from each other, so that the deformed material on the sheet can flow into the gap between the adjacent anti-torsion teeth 30, thereby achieving the anti-torsion effect. Any anti-torsion tooth 30 extends radially outward from the outer wall surface 12 along the self-clinching nut 100. In one or more embodiments, any anti-torsion tooth 30 includes a first end 31 located radially outward, and the first end 31 can be flush with the outer edge of the flange portion 20. Alternatively, the first end 31 can also be located on the inner side of the outer edge of the flange portion 20. The distance L of any first end 31 relative to the center line of the self-clinching nut 100 satisfies L≥3 / 2D. In other words, the diameter of the circle where the first end 31 is located together is at least 3 times the nominal diameter of the self-clinching nut 100, thereby meeting the anti-torsion requirements of the self-clinching nut 100 on the soft metal sheet 501 and preventing excessive sinking into the soft metal sheet 501.

[0028] Continue reading Figure 3In one or more embodiments, along the radial direction of the rivet nut 100 from inside to outside, the height h of any anti-torsion tooth 30 relative to the discharge surface 21 gradually increases. The further away the anti-torsion tooth 30 is from the center line of the rivet nut 100, the stronger the anti-torsion effect. Through the above-mentioned arrangement, part of the material of the anti-torsion tooth 30 is omitted, and the manufacturing cost is reduced while ensuring the anti-torsion effect as much as possible. Furthermore, along the radial direction of the rivet nut 100 from inside to outside, the width w of any anti-torsion tooth 30 gradually increases, and the ratio of the height h to the width w satisfies h / w≥0.9. Through the above-mentioned arrangement, the anti-torsion ability of the rivet nut 100 of the present invention on the soft plate material is much higher than that of the ordinary rivet nut 100, and it can reduce the mold clamping pressure of the rivet nut 100 installed on the plate material, thereby improving the installation efficiency.

[0029] like Figure 3 As shown, in one or more embodiments, the number of the anti-torsion teeth 30 may be 8, which are arranged at equal intervals. Alternatively, the anti-torsion teeth 30 may also be arranged in other suitable numbers, such as 6, 10, etc.

[0030] Continue reading Figure 1 and Figure 3 In one or more embodiments, the rivet nut 100 further includes a material receiving groove 40 for receiving the material flowing due to deformation on the plate. The material receiving groove 40 is formed on the outer wall surface 12 and is recessed from the outer wall surface 12 to the inside of the rivet nut 100. The material receiving groove 40 is located on the side of the flange portion 20 where the anti-torsion teeth 30 are provided. Figure 2 In the orientation shown, the material receiving groove 40 is located below the flange portion 20 , so that the rivet nut 100 can be embedded downward into the plate. Under the action of the discharge surface 21 , the material on the plate flows into the material receiving groove 40 .

[0031] Further, in one or more embodiments, the material receiving groove 40 includes a bottom surface 41 inclined toward the flange portion 20, and the bottom surface 41 is configured as a revolving surface and forms an angle with the center line of the rivet nut 100, so that after the deformed material on the plate flows into the material receiving groove 40, the movement of the rivet nut 100 along its center line direction is restricted by the flange portion 20 and the ground, respectively, to prevent the rivet nut 100 from falling off the plate. The bottom surface 41 can be connected to the discharge surface 21, and the connection method can be a rounded transition connection.

[0032] Continue reading Figure 4In one or more embodiments, a plurality of reinforcing ribs 42 are provided on the bottom surface 41. The number of reinforcing ribs 42 is the same as the number of anti-torsion teeth 30, and each reinforcing rib 42 is connected to a corresponding anti-torsion tooth 30. Any anti-torsion tooth 30 includes a second end 32 located radially inward of the rivet nut 100, and the reinforcing rib 42 is connected to the second end 32. The reinforcing rib 42 and the anti-torsion tooth 30 may be integrally formed, for example, integrally manufactured by a cold heading process. Alternatively, the reinforcing rib 42 may also be configured to be more or less than the number of the anti-torsion teeth 30. Since the soft metal sheet 501 has good ductility and the material fluidity at the edge of its mounting hole 502 is good, after the sheet material is driven to flow at the discharge surface 21, the outer wall surface 12 and the anti-torsion teeth 30, more material will flow into the material trough 40 surrounded by the bottom surface 41 and the discharge surface 21. Compared with other plates, the material flowing into the soft metal plate 501 will exert greater pressure on the thinner wall of the rivet nut 100 (in this embodiment, the intersection of the ground and the discharge surface 21) to deform the threaded hole 11. Through the above arrangement, the reinforcing rib 42 prevents the threaded hole 11 of the rivet nut 100 from being deformed or even failing, further ensuring the strength of the bottom surface 41 of the material storage groove 40, and preventing the soft metal flowing into the material storage groove 40 from being squeezed and deformed, thereby affecting the function of the threaded hole 11.

[0033] Figure 4 is a cross-sectional view of an embodiment of the fastening structure of the present invention. The present invention also provides a fastening structure 500. Figure 4 As shown, the fastening structure 500 of the present invention includes a soft metal sheet 501 and the above-mentioned rivet nut 100. In one or more embodiments, the soft metal sheet 501 is provided with a mounting hole 502, and at least a portion of the rivet nut 100 is accommodated in the mounting hole 502. The soft metal sheet 501 can be made of pure aluminum or pure copper.

[0034] In one or more embodiments, the self-clinching nut 100 includes an anti-torsion tooth 30, and the anti-torsion tooth 30 includes a first end 31 located radially outside the self-clinching nut 100, and a height h1 of the first end 31 relative to the discharge surface 21 is in a predetermined ratio with respect to the thickness of the soft metal sheet 501. The predetermined ratio is between 0.25 and 0.28. Alternatively, h1 and the thickness of the soft metal sheet 501 may also form other suitable ratios.

[0035] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A self-clinching nut for soft metal sheet material, characterized in that: The self-clinching nut comprises: A flange portion having a discharge surface adapted to abut against the plate; and A plurality of anti-torsion teeth are provided on the discharge surface and are spaced apart from each other, any of the anti-torsion teeth extend radially outward from the outer wall surface of the rivet nut, and a height h of any of the anti-torsion teeth relative to the discharge surface gradually increases from the inside to the outside along the radial direction, and any of the anti-torsion teeth includes a first end portion located radially outward, and a distance L of any of the first end portions relative to a center line of the rivet nut satisfies the following condition: L ≥ 3 / 2D with respect to a nominal diameter D of the rivet nut.

2. The self-clinching nut according to claim 1, characterized in that: Along the radial direction from inside to outside, the width w of any anti-torsion tooth gradually increases, and the ratio of the height h to the width w satisfies: h / w≥0.

9.

3. The self-clinching nut according to claim 1, characterized in that: The discharge surface is configured as a rotation surface and its center line coincides with the center line of the rivet nut, and the discharge surface is inclined away from the center line of the rivet nut.

4. The self-clinching nut according to claim 1, characterized in that: The rivet nut further includes a material receiving groove for accommodating material flowing due to deformation on the plate, wherein the material receiving groove is formed on the outer wall surface and is located on a side of the flange portion where the anti-torsion teeth are provided.

5. The self-clinching nut according to claim 4, characterized in that: The material containing groove comprises a bottom surface inclined toward the flange portion, and the bottom surface is connected to the material discharging surface; The bottom surface is provided with a plurality of reinforcing ribs extending in the direction of the center line of the rivet nut, and any of the reinforcing ribs is connected to the corresponding anti-torsion tooth.

6. The self-clinching nut according to claim 1, characterized in that: The rivet nut also includes a threaded hole, the depth D of the threaded hole p Satisfy D p ≥0.8D.

7. A fastening structure, characterized in that: The fastening structure comprises: a flexible metal sheet material, the flexible metal sheet material comprising a mounting hole; and A self-clinching nut, wherein at least a portion of the self-clinching nut is accommodated in the mounting hole and comprises: a flange portion, wherein the flange portion has a discharge surface abutting against the soft metal sheet; and a plurality of anti-torsion teeth, wherein the anti-torsion teeth are arranged on the discharge surface and are spaced apart from each other, wherein any of the anti-torsion teeth extends radially outward from the outer wall surface of the self-clinching nut, and a height h of any of the anti-torsion teeth relative to the discharge surface gradually increases from the inside to the outside along the radial direction, and wherein any of the anti-torsion teeth comprises a first end portion located radially outward, and a distance L of the first end portion relative to a center line of the self-clinching nut satisfies the following condition: L ≥ 3 / 2D with respect to a nominal diameter D of the self-clinching nut.

8. The fastening structure according to claim 7, characterized in that: A height h1 of the first end relative to the discharge surface is in a predetermined proportion to a thickness of the soft metal sheet.

9. The fastening structure according to claim 7, characterized in that: The soft metal sheet is made of pure aluminum or pure copper.

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