A core-pulling rivet and a riveting method

Abstract

The present application relates to a kind of core-pulling rivet and riveting method, core-pulling rivet includes riveting sleeve and mandrel, the riveting sleeve includes riveting body and the upper cap along of the upper end of riveting body, the mandrel includes shaft and the sharp head of the lower end of shaft, the shaft is arranged in riveting body, and sharp head is in contact with the lower end of riveting body, the riveting body includes main connecting section and lower riveting section from top to bottom, the side surface of main connecting section is conical surface, and the radius is large in the upper and small in the lower, main connecting section is used to be inserted in the workpiece to be riveted, and the length of main connecting section is greater than or equal to the thickness of the workpiece to be riveted, the side surface of lower riveting section is cylindrical surface or conical surface with the radius being large in the upper and small in the lower, and the radius of lower riveting section upper end is same with the radius of main connecting section lower end;During riveting process, the lower end of the riveting sleeve can be compressed into drum along axial direction or extruded and expanded along radial direction by sharp head in the process of pulling mandrel upward, and lower riveting cap is riveted with upper cap along to rivet the workpiece to be riveted.

Description

Technical Field

[0001] This invention relates to the field of riveting technology, and in particular to a blind rivet and a riveting method. Background Technology

[0002] In recent years, due to the increasing demands for lightweighting in aerospace, automotive and other fields, the application of materials such as aluminum alloys and magnesium alloys, as well as enclosed / semi-enclosed components, has become more and more widespread. How to achieve high-strength connection of metal / non-metal materials and enclosed / semi-enclosed structural components has become the key to achieving lightweighting.

[0003] To address the aforementioned issues, GM in the United States proposed a novel riveting process—Friction Stir Blind Riveting (FSBR). This process utilizes a rivet with a specific rotational speed and feed rate to penetrate and connect the workpieces, offering advantages such as high connection strength and fewer process constraints. The rivet in the FSBR process generally consists of two parts: a mandrel and a rivet sleeve (including an upper cap and a lower rivet body). The mandrel structure (especially the lower pointed head structure) determines the penetration force during the riveting process, while the rivet sleeve structure determines the joint strength. When testing the mechanical properties of the joint through uniaxial tensile tests, it was found that when the strength of the connected workpieces is high, the joint failure mode is usually the fracture of the lower rivet body. Force analysis of the rivet during the tensile process reveals that in the initial stage of joint tension, the rivet axis is parallel to the wall of the penetrated workpiece hole, at which point the lower rivet body is subjected to radial pressure. With continued tension, the rivet tilts under the action of bending moment, meaning the lower rivet body begins to experience axial tensile force, eventually leading to breakage and connection failure. Further analysis based on the cross-sectional observation of the joint revealed that due to issues with the rivet manufacturing and assembly processes, there was a coaxiality error between the mandrel and the rivet sleeve. As a result, when the mandrel rotates and drives the rivet sleeve to penetrate the workpiece, radial runout occurs, causing the diameter of the workpiece hole after penetration to be larger than the diameter of the lower rivet body. In other words, there is a gap between the outer surface of the lower rivet body and the workpiece material of the hole wall. The presence of this gap makes the rivet more prone to tilting during the joint stretching process, which can lead to the rivet sleeve being pulled apart.

[0004] Furthermore, for high-strength workpieces, increasing the wall thickness of the lower rivet body is an effective way to improve joint strength and ensure riveting effectiveness. For existing rivet structures, there are two ways to increase the rivet body wall thickness: a. increasing the radial diameter of the lower rivet body's outer surface, and b. decreasing the radial diameter of the lower rivet body's inner surface. However, since both the inner and outer surfaces of existing rivets are cylindrical, increasing the wall thickness using method a will increase the size of the mandrel head, thus requiring greater penetration force. In contrast, increasing the wall thickness using method b will decrease the mandrel diameter, reducing strength and potentially causing premature breakage of the mandrel during pull-out, resulting in the rivet body failing to properly lock the connected parts. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide a blind rivet and a riveting method that can simultaneously improve the strength of the rivet body and eliminate the gap between the rivet body and the workpiece hole wall after the rivet penetrates, thereby ensuring the riveting strength and the riveting effect.

[0006] To achieve the above objectives, the present invention provides a blind rivet, comprising a rivet sleeve and a mandrel. The rivet sleeve includes a rivet body and an upper cap edge at the upper end of the rivet body. The mandrel includes a shaft and a pointed head at the lower end of the shaft. The shaft passes through a rivet tube, and the pointed head abuts against the lower end of the rivet body. The rivet body includes a main connecting section and a lower riveting section from top to bottom. The side of the main connecting section is a conical surface with a larger radius at the top and a smaller radius at the bottom. The main connecting section is used to insert into the workpiece to be riveted, and the length of the main connecting section is greater than or equal to the thickness of the workpiece to be riveted. The side of the lower riveting section is a cylindrical surface or a conical surface with a larger radius at the top and a smaller radius at the bottom, and the upper radius of the lower riveting section is the same as the lower radius of the main connecting section. During the riveting process, the lower part of the rivet sleeve can be compressed axially into a drum or radially squeezed and expanded by the pointed head to form a lower rivet cap during the upward pulling of the mandrel, and the lower rivet cap and the upper cap edge together lock the workpiece to be riveted.

[0007] Furthermore, the side surface of the lower riveting section is a conical surface, and its taper is the same as that of the main connecting section.

[0008] Furthermore, the thickness of the riveted workpiece is t, the length of the main connecting section is H, the upper radius is r1, the lower radius is r2, and the coaxiality error between the rivet sleeve and the mandrel is... The cone angle α of the main connecting section's conical surface satisfies the formula

[0009] Furthermore, the rivet sleeve has a chip-receiving groove on the lower end face of the upper cap edge.

[0010] Furthermore, the lower riveting section of the rivet sleeve is provided with a compression ring groove on the inner wall of the hole, and the compression ring groove is used to form a bulge when the lower riveting section is compressed.

[0011] Furthermore, the rivet sleeve has a clamping part on the upper cap edge, which is used to cooperate with an external clamping device.

[0012] Furthermore, the mandrel has a break point annular groove on the outer circumferential surface of the shaft.

[0013] Furthermore, the pointed end of the mandrel is conical.

[0014] The present invention also provides a riveting method using the above-mentioned blind rivet, comprising the following steps:

[0015] S1. Connect the mandrel to the riveting equipment, start the riveting equipment, make the mandrel and the rivet sleeve rotate together, and apply axial pressure to make the tip of the mandrel rotate and drill a hole in the workpiece to be riveted. The mandrel and the rivet sleeve penetrate the workpiece to be riveted together, and stop rotating the mandrel when the distance between the upper edge of the rivet sleeve and the workpiece to be riveted is L, where L is greater than the thickness t of the workpiece to be riveted.

[0016] S2. Apply axial pressure to allow the mandrel and rivet sleeve to continue passing through the riveted workpiece until the upper edge of the rivet sleeve presses against the riveted workpiece.

[0017] S3. Pull the mandrel upwards. The head of the mandrel compresses the lower riveting section of the rivet sleeve or enters the lower riveting section to expand the lower riveting section, so that the lower end of the rivet sleeve forms a lower rivet cap. The workpiece to be riveted is pressed and fixed between the upper rivet cap and the lower rivet cap.

[0018] S4. The mandrel breaks off near the upper end of the rivet sleeve, forming the final riveted joint.

[0019] Furthermore, in step S1, the distance L is less than or equal to the length H of the main connection segment.

[0020] As described above, the blind rivet and riveting method of the present invention have the following beneficial effects:

[0021] The rivet body, consisting of a main connecting section and a lower rivet section, is used by rotating the mandrel and rivet body together while applying axial pressure. The mandrel and rivet body pass through the workpiece to be riveted, forming a rivet hole in the workpiece. The mandrel stops rotating when the distance between the upper cap of the rivet sleeve and the workpiece is L. Due to the coaxiality deviation between the mandrel and the rivet body, there will be a gap between the wall of the rivet hole and the rivet body at this time. Then, the mandrel and rivet body stop rotating, and only axial pressure is applied. The mandrel and rivet body continue to pass through the workpiece in a straight line until the upper cap of the rivet sleeve presses against the workpiece. Since the side of the main connecting section is conical, the radius gradually increases during the pressing process, which can continuously compress the workpiece material, ensuring that the main connecting section is in close contact with the wall of the rivet hole without any gaps. The blind rivet of the present invention has the following advantages: First, it can effectively eliminate the gap between the rivet body and the workpiece being riveted, ensuring close contact between the two and making the riveting effect of the rivet body more stable and reliable. Second, given a fixed outer diameter radius at the upper end of the rivet body, the smaller size at the lower end of the rivet body reduces the size of the mandrel end, thereby reducing the penetrating force when the rivet penetrates and preventing excessive deformation of the workpiece being riveted, which would affect the joint strength. Third, because the lower end of the rivet body is small, it is easily compressed into a drum or expanded by squeezing. Therefore, the pulling force required when the mandrel is pulled upwards for riveting is small, and the radius of the mandrel is small, which reduces the radius of the inner hole of the rivet body, thereby increasing the wall thickness of the rivet body, especially the main connecting end, and ensuring the riveting effect. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a first embodiment of the blind rivet of the present invention.

[0023] Figure 2 for Figure 1 Top view.

[0024] Figure 3 for Figure 1 Sectional view along the AA direction.

[0025] Figure 4 for Figure 3 Enlarged view of circle B in the image.

[0026] Figure 5 for Figure 3 Enlarged view of circle C in the image.

[0027] Figure 6 This is a schematic diagram of the working process of the pop rivet of the present invention.

[0028] Figure 7 This is a schematic diagram of the structure of a second embodiment of the blind rivet of the present invention.

[0029] Component designation explanation

[0030] 1 mandrel

[0031] 11. Pointed head

[0032] 12 shafts

[0033] 13. Discontinuity annular groove

[0034] 2 Rivet sleeve

[0035] 21. Upper brim

[0036] 22 Main Connector Section

[0037] 23 Lower Rivet Section

[0038] 24 Clamping section

[0039] 25 Chip Collection Grooves

[0040] 26 Compression ring groove

[0041] 3. Workpieces to be riveted Detailed Implementation

[0042] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0043] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0044] See Figures 1 to 7 This invention provides a blind rivet for riveting a workpiece 3 composed of multiple stacked parts. The blind rivet includes a rivet sleeve 2 and a mandrel 1. The rivet sleeve 2 includes a rivet body and an upper cap 21 at the upper end of the rivet body. The mandrel 1 includes a shaft 12 and a pointed head 11 at the lower end of the shaft 12. The shaft 12 passes through the rivet body, and the pointed head 11 abuts against the lower end of the rivet body. The rivet body includes a main connecting section 22 and a lower riveting section 23 from top to bottom. The side of the main connecting section 22 is conical, and the radius is larger at the top and smaller at the bottom, that is, the main connecting section 22 is frustum-shaped. The main connecting section 22 is used for... The main connecting section 22 is inserted into the workpiece 3 being riveted, and its length is greater than or equal to the thickness of the workpiece 3 being riveted. The side of the lower riveting section 23 is a cylindrical surface or a conical surface with a larger radius at the top and a smaller radius at the bottom. That is, the lower riveting section 23 can be cylindrical or frustum-shaped, and the upper radius of the lower riveting section 23 is the same as the lower radius of the main connecting section 22. During the riveting process, the lower part of the rivet sleeve 2 can be compressed axially into a drum or radially squeezed and expanded by the pointed head 11 to form a lower rivet cap during the upward pulling of the mandrel 1. The lower rivet cap and the upper cap edge 21 are riveted together to the workpiece 3 being riveted. In this invention, when the mandrel 1 rotates, it drives the rivet sleeve 2 to rotate. The two are generally transmitted through friction. Of course, torsional force can also be transmitted through other structures. This part is prior art and will not be described in detail here.

[0045] The basic working principle of the blind rivet involved in this invention is as follows: See Figure 1 ,in Figure 1Only the structure of the riveted workpiece 3 is shown. In use, the mandrel 1 is connected to the riveting equipment, the equipment is started, causing the mandrel 1 and the rivet sleeve 2 to rotate together, and axial pressure is applied, causing the tip 11 of the mandrel 1 to rotate and drill a hole in the riveted workpiece 3. The mandrel 1 and the rivet sleeve 2 pass through the riveted workpiece 3 together, forming a riveting hole in the workpiece 3. The rotation of the mandrel 1 is stopped when the distance between the upper cap edge 21 of the rivet sleeve 2 and the riveted workpiece 3 is L, where L is greater than the thickness t of the riveted workpiece 3 and is generally less than or equal to the length H of the main connecting section 22. During this process, due to the coaxiality deviation between the mandrel 1 and the rivet sleeve 2, the riveted part... There will be a gap between the riveting hole wall in workpiece 3 and the rivet sleeve 2; then the mandrel 1 and the rivet sleeve 2 stop rotating and only apply axial pressure, so that the mandrel 1 and the rivet sleeve 2 continue to pass through the riveted workpiece 3 in a straight line until the upper cap edge 21 of the rivet sleeve 2 presses against the riveted workpiece 3. At this time, the main connecting section 22 is exactly in the riveting hole of the riveted workpiece 3, while the lower riveting section 23 passes through the riveted workpiece 3. During this process, since the side of the main connecting section 22 is a conical surface, the radius gradually increases during the pressing process, which can continuously squeeze the workpiece material and ensure that the main connecting section 22 is in close contact with the riveting hole wall without any gap. Then the mandrel 1 is pulled upward, and the tip 11 of the mandrel 1 compresses the lower riveting section 23 of the rivet sleeve 2, so that the lower end of the rivet sleeve 2 forms a bulge, or enters the lower riveting section 23 to expand the lower riveting section 23. In this way, a lower rivet cap is formed at the lower end of the rivet sleeve 2, and the riveted workpiece 3 is pressed and fixed between the upper cap edge 21 and the lower rivet cap.

[0046] The blind rivet of the present invention has the following advantages: First, it can effectively eliminate the gap between the rivet sleeve 2 and the riveted workpiece 3, ensuring close contact between the two and making the riveting effect of the rivet sleeve 2 more stable and reliable. Second, compared with the existing cylindrical rivet sleeve 2, with a fixed outer diameter of the upper end of the main connecting section 22, the outer diameter of the lower end of the riveting section 23 can be reduced, thereby reducing the size of the tip 11 of the mandrel 1 and reducing the penetration force during the penetration process. Third, the reduction in the outer diameter of the lower end of the riveting section 23 can also reduce the force required when the lower end of the rivet sleeve 2 is compressed or expanded to form the lower rivet cap, thereby reducing the diameter of the mandrel 1 and increasing the wall thickness of the rivet body, especially the main connecting section 22, thereby increasing the riveting effect of the rivet sleeve 2.

[0047] See Figures 1 to 7 The present invention will be further illustrated below with two specific embodiments:

[0048] Example 1:

[0049] See Figures 1 to 6 The structure and operation of this embodiment are illustrated below. In this embodiment, see [link to relevant documentation]. Figure 1 and Figure 3The lower end of the lower riveting section 23 is cylindrical, and the upper end of the lower riveting section 23 has the same radius as the lower end of the main connecting section 22, and the two are preferably smoothly connected. Using a cylindrical lower riveting section 23, compared to a frustum-shaped lower riveting section 23, results in a smaller radius at the lower end of the lower riveting section 23 where the rivet cap is formed, given a fixed upper radius. Therefore, the force required to form the rivet cap is also smaller, which allows for a smaller core diameter. Consequently, the main connecting section 22 can have a larger wall thickness, ensuring its strength.

[0050] In this embodiment, see Figure 1 and Figure 6 The thickness of the riveted workpiece 3 is t, the length of the main connecting section 22 is H, the upper radius is r1, the lower radius is r2, and the coaxiality error between the rivet sleeve 2 and the mandrel 1 is... As a preferred design, the cone angle α of the main connecting section 22 cone surface satisfies the formula At this time, the main connecting section 22 makes better and tighter contact with the riveting hole wall in the riveted part, eliminates gaps, avoids the riveting sleeve 2 from tilting, and ensures the riveting effect.

[0051] In this embodiment, see Figure 3 and Figure 6 As a preferred design, the rivet sleeve 2 has a chip-receiving groove 25 on the lower end face of the upper cap 21. The inner edge of the chip-receiving groove 25 is close to the side wall of the main connecting section 22. The chip-receiving groove 25 is used to accommodate the workpiece material debris that flows upward due to the squeezing action during the process of the pop rivet penetrating the riveted workpiece 3.

[0052] In this embodiment, the lower end of the rivet sleeve 2 is compressed by the pointed head 11 of the mandrel 1 to form a bulge, resulting in a lower rivet cap. This lower rivet cap can be formed solely by the lower rivet section 23 (when the length H of the main connecting section 22 is equal to the thickness of the riveted workpiece 3), or it can be formed by the lower rivet section 23 and part of the main connecting section 22 (when the length H of the main connecting section 22 is greater than the thickness of the riveted workpiece 3). The pointed head 11 of the mandrel 1 is conical, and the upper radius of the pointed head 11 is equal to or slightly larger than the lower radius of the lower rivet section 23. Of course, the pointed head 11 can also adopt other suitable shapes. See [link to documentation]. Figure 3 and Figure 5 As a preferred design, in this embodiment, the lower riveting section 23 of the rivet sleeve 2 has a compression ring groove 26 on its inner wall. When the lower riveting section 23 is compressed, the compression ring groove 26 helps to form a bulge to lock the riveted workpiece 3. The position of the compression ring groove 26 can also be varied according to the thickness of the riveted workpiece 3.

[0053] In this embodiment, see Figure 1 , Figure 2 and Figure 3As a preferred design, the rivet sleeve 2 has a clamping part 24 at the upper end of the upper cap 21. The clamping part 24 can take various shapes and is used to cooperate with external clamping devices. During riveting, in addition to the torque transmitted from the spindle 1, the rivet sleeve 2 is clamped in the clamping part 24 by the corresponding external clamping device to apply force synchronously, so that the rivet sleeve 2 and the spindle 1 rotate and press down together, avoiding problems such as the spindle breaking due to the force applied to the spindle 1 alone, and the relative sliding between the two caused by the torque exceeding the friction between the rivet sleeve and the spindle.

[0054] In this embodiment, see Figure 3 and Figure 5 As a preferred design, the mandrel 1 has a break-point groove 13 on the outer circumferential surface of the shaft 12. After the riveting sleeve 2 has riveted the workpiece 3, the break-point groove 13 is located at the upper end of the riveting sleeve 2, and then the mandrel 1 is broken at the break-point groove 13. The shaft 12 of the mandrel 1 is used to connect with the riveting equipment, and its shape can be cylindrical or other shapes, such as a hexagonal column.

[0055] Example 2:

[0056] See Figure 7 This embodiment is basically the same in structure as Embodiment 1 above, except that the lower riveting section 23 of the rivet sleeve 2 is frustum-shaped, and the taper of its side is the same as the taper of the side of the main connecting section 22. That is, the lower riveting section 23 and the main connecting section 22 are perfectly connected to form an integral frustum, which facilitates the manufacture of the rivet sleeve 2 and reduces the processing difficulty. Compared with Embodiment 1, with a fixed lower radius of the lower riveting section 23, the wall thickness of the main connecting section 22 is smaller, which can be used when the strength requirement of the rivet sleeve 2 is lower.

[0057] In the two embodiments of the present invention described above, the lower rivet cap is obtained by compressing the lower end of the rivet sleeve 2 with the mandrel 1 to form a bulge. In other embodiments, the tip 11 of the mandrel 1 can also be used to enter the lower rivet section 23 to expand the lower end of the rivet sleeve 2 and form the lower rivet cap. This method is also commonly used in the field of blind rivets. The specific structure and principle will not be described in detail here.

[0058] The present invention also provides a riveting method using the above-mentioned blind rivet, comprising the following steps:

[0059] S1. Connect the mandrel 1 to the riveting equipment, start the riveting equipment, make the mandrel 1 and the rivet sleeve 2 rotate together, and apply axial pressure to make the tip 11 of the mandrel 1 rotate and drill a hole in the workpiece 3 to be riveted. The mandrel 1 and the rivet sleeve 2 penetrate the workpiece 3 together, and stop rotating the mandrel 1 when the distance between the upper cap edge 21 of the rivet sleeve 2 and the workpiece 3 to be riveted is L, where L is greater than the thickness t of the workpiece 3 to be riveted, and L is generally less than or equal to the length H of the main connecting section 22.

[0060] S2. Apply axial pressure to make the mandrel 1 and the rivet sleeve 2 continue to pass through the riveted workpiece 3. At this time, the mandrel 1 and the rivet sleeve 2 do not rotate until the upper cap edge 21 of the rivet sleeve 2 presses against the riveted workpiece 3.

[0061] S3. Pull the mandrel 1 upwards. The head of the mandrel 1 compresses the lower riveting section 23 of the rivet sleeve 2, or enters the lower riveting section 23 to expand it, so that the lower end of the rivet sleeve 2 forms a lower rivet cap. The workpiece 3 to be riveted is pressed and fixed between the upper cap edge 21 and the lower rivet cap. At this time, the break point annular groove 13 on the mandrel 1 is exactly located at the upper end of the rivet sleeve 2. Since there has been a rotation process in the previous step S2, the material of the workpiece 3 to be riveted has been softened by the heat generated by friction. Therefore, the mandrel 1 and the rivet sleeve 2 can smoothly pass through the workpiece 3 in a straight line.

[0062] S4. The mandrel 1 is broken near the upper end of the rivet sleeve 2, specifically by using the break point annular groove 13 to form the final riveted joint.

[0063] As can be seen from the above, the blind rivet and the riveting method using the blind rivet in this embodiment have the following advantages:

[0064] 1. By designing a new rivet sleeve 2 structure and changing the riveting operation method, the rivet sleeve 2 and the riveted workpiece 3 are in close contact when the blind rivet penetrates the workpiece 3 being riveted, without any gap. This avoids the problem of the rivet sleeve 2 tilting or even breaking and failing, ensuring the riveting effect and eliminating various problems caused by the coaxiality error between the rivet sleeve 2 and the mandrel 1.

[0065] 2. While ensuring a constant upper radius of the rivet body, the lower size of the rivet body and the end size of the mandrel can be effectively reduced, thereby reducing the penetrating force when the rivet penetrates. Furthermore, due to the small lower size of the rivet body, it is easy to be compressed into a drum or squeezed and expanded. The mandrel requires less pulling force when riveting, which can reduce the radius of the mandrel and increase the wall thickness of the rivet body, especially the main connecting end, thus ensuring the riveting effect.

[0066] 3. Under the condition that the penetration force of the blind rivet (the head size of the blind rivet) is constant, the wall thickness of the main connecting section 22 of the rivet sleeve 2 can be increased, the strength of the rivet sleeve 2 can be increased, thereby increasing the riveting effect of the rivet sleeve 2, and without affecting the compression or expansion of the lower end of the rivet sleeve 2.

[0067] 4. The rivet sleeve 2 and the mandrel 1 can be subjected to force simultaneously, avoiding the problem of breakage caused by the mandrel 1 being subjected to force alone.

[0068] 5. In the process of riveting, the chip groove 25 is used to accommodate the workpiece material flowing upward under the extrusion action, ensuring a smooth riveting process.

[0069] In conclusion, the invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0070] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method of riveting, characterized by: The method is performed by using a core-pulling rivet, the core-pulling rivet comprising a rivet sleeve (2) and a mandrel (1), the rivet sleeve (2) comprising a rivet body and an upper cap edge (21) at an upper end of the rivet body, the mandrel (1) comprising a shaft (12) and a pointed head (11) at a lower end of the shaft (12), the shaft (12) being arranged in the rivet body and the pointed head (11) abutting a lower end of the rivet body, characterized in that: the rivet body comprises a main connecting section (22) and a lower riveting section (23) from top to bottom, a side surface of the main connecting section (22) is a tapered surface with a radius that is large at top and small at bottom, the main connecting section (22) is used to be inserted into a riveted workpiece (3), and a length of the main connecting section (22) is greater than or equal to a thickness of the riveted workpiece (3), a side surface of the lower riveting section (23) is a cylindrical surface or a tapered surface with a radius that is large at top and small at bottom, and a top end radius of the lower riveting section (23) is the same as a bottom end radius of the main connecting section (22); during riveting, a lower end part of the rivet sleeve (2) is compressed into a drum along an axial direction or is extruded and expanded along a radial direction to form a lower riveting cap by the pointed head (11) during upward pulling of the mandrel (1), and the lower riveting cap, together with the upper cap edge (21), locks the riveted workpiece (3), the thickness of the riveted workpiece (3) is t, the length of the main connecting section (22) is H, the top end radius of the main connecting section (22) is r1, the bottom end radius of the main connecting section (22) is r2, and a coaxiality error of the rivet sleeve (2) and the mandrel (1) is a tapered angle α of the tapered surface of the main connecting section (22) satisfies a formula the riveting method comprises the following steps: S1, connecting the mandrel (1) to the riveting equipment, starting the riveting equipment, rotating the mandrel (1) and the riveting sleeve (2) together, and applying axial pressure, so that the pointed head (11) of the mandrel (1) rotates to drill a hole on the riveted workpiece (3), the mandrel (1) and the riveting sleeve (2) penetrate the riveted workpiece (3) together, and the rotation of the mandrel (1) is stopped when the distance between the upper cap edge (21) of the riveting sleeve (2) and the riveted workpiece (3) is L, wherein L is greater than the thickness t of the riveted workpiece (3); S2, applying axial pressure to make the mandrel (1) and the riveting sleeve (2) continue to penetrate the riveted workpiece (3), and the mandrel (1) and the riveting sleeve (2) do not rotate until the upper cap edge (21) of the riveting sleeve (2) is pressed against the riveted workpiece (3); S3, pulling the mandrel (1) upwards, the head of the mandrel (1) compresses the lower riveting section (23) of the riveting sleeve (2), or enters the lower riveting section (23) to expand the lower riveting section (23), so that the lower end of the riveting sleeve (2) forms a lower riveting cap, and the riveted workpiece (3) is tightly fixed between the upper cap edge (21) and the lower riveting cap; S4, the mandrel (1) is disconnected at a position close to the upper end of the riveting sleeve (2), forming a final riveting joint.

2. The riveting method according to claim 1, characterized in that: In the step S1, the distance L is less than or equal to the length H of the main connecting section (22).

3. The riveting method according to claim 1, characterized in that: The side surface of the lower riveting section (23) is a tapered surface, and the taper thereof is the same as that of the tapered surface of the main connecting section (22).

4. The riveting method according to claim 1, characterized by: The riveting sleeve (2) is provided with a circle of chip grooves (25) on the lower end surface of the upper cap edge (21).

5. The riveting method according to claim 1, characterized by: The lower riveting section (23) of the riveting sleeve (2) is provided with a compression ring groove (26) on the inner hole wall, and the compression ring groove (26) is used to form a bulge when the lower riveting section (23) is compressed.

6. The riveting method of claim 1, wherein: The riveting sleeve (2) is provided with a clamping part (24) on the upper cap edge (21), and the clamping part (24) is used to cooperate with an external clamping device.

7. The riveting method according to claim 1, characterized by: The mandrel is provided with a breakpoint ring groove (13) on the outer peripheral surface of the shaft rod (12).

8. The riveting method of claim 1, wherein: The pointed head (11) of the mandrel (1) is conical.

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