Internal expansion fixed rivet and manufacturing method thereof

Abstract

The invention provides an internal expansion fixed rivet and a manufacturing method thereof, and relates to the technical field of rivets. The sleeve seat is of a cylindrical tubular structure, a cap body is formed at one end of the upper portion of the sleeve seat in an extrusion mode, the rivet core is inserted into the sleeve seat, a punch is formed at one end of the lower portion of the rivet core in an extrusion mode, threads are formed at one end of the upper portion of the rivet core, and two auxiliary grooves are symmetrically formed in the inner wall of the sleeve seat and are each of an annular groove-shaped structure. And the two auxiliary grooves are guide structures for deformation of the sleeve seat. The symmetrical annular auxiliary grooves are formed in the inner wall of the sleeve seat, the rectangular auxiliary holes in the annular array are formed in the corresponding positions of the outer wall, the double structures act synergistically, the deformation resistance of the sleeve seat in the riveting process can be effectively reduced, the traction force borne by the rivet core is reduced, and therefore the risk that the rivet core is broken due to too large stress is greatly reduced, and the riveting quality is improved. And the overall durability of the rivet is improved.

Description

Technical Field

[0001] This invention relates to the field of rivet technology, and in particular to an internal expansion fixing rivet and its manufacturing method. Background Technology

[0002] A rivet is a mechanical fastener used to permanently or semi-permanently connect two or more components together. It is widely used in machinery manufacturing, construction engineering, aerospace, automotive industry and other fields.

[0003] The existing device is prone to excessive resistance during riveting, which can cause the rivet core to break. The existing device cannot provide auxiliary fixation after riveting, resulting in poor fixation effect. Summary of the Invention

[0004] This invention relates to an internal expansion fixing rivet and its manufacturing method, which solves the problems of existing devices causing excessive resistance and rivet core breakage during riveting, and the inability of existing devices to achieve auxiliary fixing after riveting, resulting in poor fixing effect.

[0005] This invention provides an internally expanding fixed rivet and its manufacturing method, specifically including: a sleeve; the sleeve is a cylindrical tubular structure, with a cap body extruded at one end of the sleeve, a rivet core inserted inside the sleeve, a punch extruded at one end of the rivet core, and a threaded end at one end of the rivet core; two auxiliary grooves are symmetrically opened on the inner wall of the sleeve, both of which are annular groove structures, and the two auxiliary grooves are guiding structures for the deformation of the sleeve.

[0006] Furthermore, the outer wall of the sleeve is provided with auxiliary holes in a ring array. The auxiliary holes are rectangular holes and are aligned with the auxiliary grooves.

[0007] Furthermore, the diameter of the punch is larger than the diameter of the nail core, and there is a transition process between the punch and the nail core.

[0008] Furthermore, a reinforcing rod is provided inside the nail core. The reinforcing rod is a cylindrical rod-shaped structure and is made of high-hardness steel.

[0009] Furthermore, positioning blocks are welded at equal intervals on the reinforcing rod. The positioning blocks are annular block structures, and the reinforcing rod and positioning blocks form a nail core reinforcement structure.

[0010] Furthermore, a blocking assembly is fitted onto the sleeve, the blocking assembly consisting of a retaining ring and an auxiliary rod. The retaining ring is fitted onto the sleeve, the retaining ring having a ring structure, and the upper end face of the retaining ring contacting the cap body.

[0011] Furthermore, four auxiliary rods are welded in a ring array on the lower end face of the sleeve, and the four auxiliary rods are welded at an angle.

[0012] Furthermore, the lower end of the punch is polished, and after polishing, the lower end of the punch has a frustum-shaped structure.

[0013] A method for manufacturing an internal expansion fixing rivet includes the following steps: 01. As one of the main load-bearing structures of the rivet, the socket needs to have good plasticity and strength. According to its application scenario (such as metal component connection, equipment assembly, etc.) and performance requirements, a cylindrical aluminum alloy tube with an appropriate diameter is selected. Aluminum alloy is not only lightweight, but also maintains stable mechanical properties during extrusion deformation, which is suitable for the plastic deformation requirements in the riveting process. After selection, the tube needs to be preliminarily inspected to remove blanks with scratches, dents or air bubbles on the surface to ensure the quality of raw materials. 02. According to the design dimensions, use a high-precision tube cutting machine to cut the aluminum alloy tube into blanks of a specific length. During the cutting process, the cut must be kept perpendicular to the tube axis, and the error must be controlled within 0.1mm to avoid eccentricity problems in subsequent processing. After cutting, fix the blank on a CNC grinding machine and rough grind both ends to remove burrs and oxide layers, so that the flatness of the end face reaches 0.05mm / m, laying the foundation for subsequent processing. At this time, the initial sleeve is formed. 03. Fix the rough-ground sleeve onto a CNC lathe and symmetrically machine two annular auxiliary grooves on the inner wall. The depth and width of the auxiliary grooves must strictly follow the design parameters, and the bottom of the grooves should be rounded to reduce stress concentration. Subsequently, machine rectangular auxiliary holes in an annular array on the outer wall of the sleeve. The position of the holes must be precisely aligned with the auxiliary grooves (coaxiality error ≤ 0.03mm). During the machining process, use a cooling system to continuously cool down the aluminum alloy to prevent deformation due to high temperature, and ensure the dimensional accuracy of the auxiliary grooves and auxiliary holes, providing a structural foundation for smooth deformation during subsequent riveting. 04. Place the sleeve with the auxiliary groove and auxiliary hole processed into a special extrusion die, and apply a set pressure (adjusted according to the aluminum alloy grade, usually 50-80MPa) through a hydraulic press to extrude one end of the sleeve to form a cap; during the extrusion process, the temperature and pressure of the die must be monitored in real time to ensure that the cap has a full shape, consistent size, and a smooth transition with the main body of the sleeve, without cracks or wrinkles; after forming, the surface of the cap is finely polished to achieve a roughness of Ra0.8μm; 05. The core reinforcement structure of the nail core is a reinforcing rod made of high-hardness steel. High-quality alloy round steel (such as 40Cr) with a suitable diameter is selected and tempered (hardness reaches HRC35-40) as the base material for the reinforcing rod. Circular positioning blocks are welded at equal intervals on the outer wall of the reinforcing rod. The positioning blocks are made of the same material as the reinforcing rod and are welded by argon arc welding. The weld height is ≥1mm and must be inspected for defects such as incomplete welding and slag inclusions. After welding, the surface of the positioning blocks is ground to make it smoothly transition with the outer wall of the reinforcing rod. 06. Place the reinforcing rod with the assembled positioning block into a special forming mold, ensuring that the mold cavity perfectly matches the shape of the nail core and punch. After preheating the mold to 200-250℃, inject molten aluminum alloy into the cavity (temperature controlled at 680-720℃) to ensure that the aluminum alloy fully fills the mold gaps and wraps around the reinforcing rod and positioning block. After pouring, allow the mold to cool naturally to room temperature and remove the blank. At this point, the punch has been integrally formed during the pouring process and forms a smooth transition with the nail core body (transition fillet radius ≥ 2mm), reducing the risk of stress concentration. 07. Fix the cast nail core blank on a CNC machine tool and grind both ends to ensure a smooth surface. Then, focus on processing the punch: use a grinding wheel to grind its lower end until a frustum-shaped structure is formed (the taper is set according to the riveting requirements, usually 15°-30°), and polish the conical surface to reduce the resistance when passing through the workpiece during riveting. During the grinding process, use a micrometer to measure the dimensions in real time to ensure that the diameter of the punch is larger than the diameter of the nail core body, and that there are no steps at the transition between the two. 08. Machin an external thread at one end of the rivet core. The thread specification is determined according to assembly requirements (such as M6, M8, etc.). Use a rolling process to ensure that the thread profile is full and the accuracy reaches 6g level. After machining, put the rivet core into a special extrusion die for secondary extrusion to further optimize the transition structure between the punch and the rivet core and enhance the overall strength. Finally, clean and deburr the surface of the rivet core to ensure that there are no sharp protrusions. 09. First, fit the retaining ring onto the sleeve base, ensuring that the upper end face of the retaining ring is in close contact with the cap body (gap ≤ 0.02mm), and fix it with an interference fit; then, weld four auxiliary rods in a ring array on the lower end face of the sleeve base. The auxiliary rods are made of high-strength aluminum alloy and are arranged at an angle (angle 30°-45°). The welding points need to be inspected for flaws to ensure the connection strength. 010. During assembly, pass the rivet core through the sleeve from bottom to top to ensure that the coaxiality error between the two is ≤0.05mm; after assembly, perform surface galvanizing treatment on the rivet: first pickling to remove rust and remove the surface oxide layer, then electroplating to form a uniform zinc layer (thickness 8-12μm), and finally passivation treatment to improve corrosion resistance; after galvanizing, the threads and mating surfaces need to be cleaned to ensure that the assembly performance is not affected.

[0014] This invention provides an internal expansion fixing rivet and its manufacturing method, which has the following beneficial effects: This application provides symmetrical annular auxiliary grooves on the inner wall of the socket and rectangular auxiliary holes in an annular array at the corresponding position on the outer wall. The dual structure works together to effectively reduce the deformation resistance of the socket during riveting and reduce the traction force on the rivet core, thereby significantly reducing the risk of the rivet core breaking due to excessive force and improving the overall durability of the rivet.

[0015] The rivet core and punch in this application adopt a transition design, with the punch diameter being larger than that of the rivet core and the two smoothly connected, avoiding stress concentration and further reducing the probability of breakage at the connection. At the same time, a reinforcing rod made of high-hardness steel is embedded inside the rivet core, and annular positioning blocks are welded at intervals on the reinforcing rod. Through the high strength characteristics of the reinforcing rod and the stress-dispersing effect of the positioning blocks, the structural strength of the rivet core is significantly enhanced, further reducing the risk of breakage and enabling the rivet to remain stable even when subjected to large traction forces.

[0016] The retaining ring fitted onto the sleeve in this application is in close contact with the cap body. After riveting, it can effectively block the impact of external forces on the cap body, prevent the cap body from slipping under force, and improve the stability of riveting. The four auxiliary rods welded at an incline on the lower end face of the sleeve will pass through the riveted material during the riveting process. After the sleeve deforms, they are squeezed and bent to form an auxiliary fixing structure. Together with the deformed part of the sleeve, they greatly improve the overall firmness after riveting and prevent the connection from loosening.

[0017] The lower end of the punch in this application is ground to form a frustum-shaped structure, which can more easily pass through the riveted object, simplifying the operation process and improving construction efficiency. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below.

[0019] The accompanying drawings described below are only related to some embodiments of the invention and are not intended to limit the invention.

[0020] In the attached diagram: Figure 1 A schematic axial view of the internal expansion fixing rivet of the present invention is shown; Figure 2 This diagram shows a schematic front view of the internal expansion fixing rivet of the present invention. Figure 3 A schematic diagram of the split axial view of the internal expansion fixing rivet of the present invention is shown. Figure 4 The present invention is shown. Figure 3 A magnified structural diagram at point A; Figure 5 The present invention is shown. Figure 2 A schematic diagram of the further disassembled axial view structure; Figure 6 The present invention is shown. Figure 5 A schematic diagram of the rotated axial view structure; Figure 7 The present invention is shown. Figure 6 A magnified structural diagram at point B; Figure 8A schematic diagram of the axial structure of the blocking component of the present invention is shown.

[0021] List of reference numerals 1. Sleeve base; 101. Auxiliary hole; 102. Auxiliary groove; 103. Cap body; 2. Nail core; 201. Punch; 202. Reinforcing rod; 203. Positioning block; 3. Blocking assembly; 301. Retaining ring; 302. Auxiliary rod. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: Please refer to Figures 1 to 8 : This invention proposes an internal expansion fixed rivet and its manufacturing method, comprising: a sleeve 1; the sleeve 1 is a cylindrical tubular structure, with a cap 103 extruded at one end of the upper part of the sleeve 1, a rivet core 2 inserted inside the sleeve 1, a punch 201 extruded at one end of the lower part of the rivet core 2, and a threaded end at one end of the upper part of the rivet core 2; two auxiliary grooves 102 are symmetrically formed on the inner wall of the sleeve 1, both auxiliary grooves 102 are annular groove structures, and the two auxiliary grooves 102 are guiding structures for the deformation of the sleeve 1. In use, when the rivet core 2 moves upward, it presses the lower end of the sleeve 1, at which time the sleeve 1 begins to deform at the two auxiliary grooves 102, and finally the riveting is completed. Under the action of the two auxiliary grooves 102, the difficulty of deformation of the sleeve 1 can be reduced, thus reducing the probability of the rivet core 2 breaking due to excessive force during the traction process.

[0024] Among them, auxiliary holes 101 are arranged in a ring array on the outer wall of the sleeve 1. The auxiliary holes 101 are rectangular holes. The auxiliary holes 101 arranged in a ring array are aligned with the auxiliary grooves 102. When the nail core 2 moves upward, the auxiliary grooves 102 arranged in a ring array can further reduce the deformation difficulty at the deformation point of the sleeve 1, thereby further reducing the probability of the nail core 2 breaking under stress.

[0025] The diameter of the punch 201 is larger than that of the nail core 2. The punch 201 and the nail core 2 are transitioned together. When the nail core 2 is subjected to traction force, the probability of breakage at the nail core 2 and the punch 201 can be reduced, and the structure is more stable.

[0026] The nail core 2 is equipped with a reinforcing rod 202, which is a cylindrical rod structure and made of high-hardness steel.

[0027] Among them, positioning blocks 203 are welded at equal intervals on the reinforcing rod 202. The positioning blocks 203 are ring-shaped block structures. The reinforcing rod 202 and the positioning blocks 203 are the reinforcing structures of the nail core 2. When the nail core 2 is subjected to traction force, the probability of the nail core 2 breaking can be reduced again under the action of the reinforcing rod 202 and the positioning blocks 203.

[0028] Among them, the sleeve 1 is fitted with a blocking component 3, which consists of a retaining ring 301 and an auxiliary rod 302. The retaining ring 301 is fitted on the sleeve 1. The retaining ring 301 has a ring structure. The upper end face of the retaining ring 301 contacts the cap body 103. After the riveting is completed, the retaining ring 301 can block the riveting, improve the stability of the riveting, and prevent the cap body 103 from slipping under force, making the riveting more stable.

[0029] Among them, four auxiliary rods 302 are welded in a ring array on the lower end face of the sleeve 1. The four auxiliary rods 302 are welded in an inclined position. During the riveting process, the four auxiliary rods 302 will pass through the riveted object. After the sleeve 1 deforms, it will squeeze the four auxiliary rods 302. When the four auxiliary rods 302 are squeezed, they will bend to complete the auxiliary fixation, which ultimately improves the stability after riveting.

[0030] Example 2, based on Example 1, such as Figures 1-8 As shown, the lower end of the punch 201 is polished, and after polishing, the lower end of the punch 201 has a frustum-shaped structure. During riveting, because the lower end of the punch 201 has a frustum-shaped structure, it can pass through the riveted object more easily, making it highly practical.

[0031] A method for manufacturing an internal expansion fixing rivet includes the following steps: 01. As one of the main load-bearing structures of the rivet, the socket 1 needs to have good plasticity and strength. According to its application scenarios such as metal component connection, equipment assembly, and performance requirements, a cylindrical aluminum alloy tube with an appropriate diameter is selected. Aluminum alloy is not only lightweight, but also maintains stable mechanical properties during extrusion deformation, which is suitable for the plastic deformation requirements in the riveting process. After selection, the tube needs to be preliminarily inspected to remove blanks with scratches, dents or internal air bubbles to ensure the quality of raw materials. 02. According to the design dimensions, use a high-precision tube cutting machine to cut the aluminum alloy tube into blanks of a specific length; during the cutting process, the cut must be kept perpendicular to the tube axis, and the error must be controlled within 0.1mm to avoid eccentricity problems in subsequent processing; after cutting, fix the blank on a CNC grinding machine and rough grind both ends to remove burrs and oxide layers, so that the flatness of the end face reaches 0.05mm / m, laying the foundation for subsequent processing. At this time, the initial sleeve 1 is formed. 03. Fix the rough-ground sleeve 1 on a CNC lathe and symmetrically machine two annular auxiliary grooves 102 on the inner wall. The depth and width of the auxiliary grooves 102 must be strictly in accordance with the design parameters, and the bottom of the grooves should be rounded to reduce stress concentration. Then, machine rectangular auxiliary holes 101 in an annular array on the outer wall of the sleeve 1. The position of the holes must be precisely aligned with the auxiliary grooves 102, and the coaxiality error should be ≤0.03mm. During the machining process, use a cooling system to continuously cool down the aluminum alloy to prevent deformation due to high temperature, and ensure the dimensional accuracy of the auxiliary grooves 102 and auxiliary holes 101, so as to provide a structural basis for smooth deformation during subsequent riveting. 04. Place the sleeve 1 with the auxiliary groove 102 and auxiliary hole 101 machined into a special extrusion mold. Apply a set pressure using a hydraulic press, which is adjusted according to the aluminum alloy grade, usually 50-80MPa, to extrude one end of the sleeve 1 to form a cap 103. During the extrusion process, the temperature and pressure changes of the mold must be monitored in real time to ensure that the cap 103 has a full shape, consistent size, and a smooth transition with the main body of the sleeve 1, without cracks or wrinkles. After forming, the surface of the cap 103 is finely polished to achieve a roughness of Ra0.8μm. 05. The core reinforcement structure of the nail core 2 is a reinforcement rod 202 made of high-hardness steel. High-quality alloy round steel with a suitable diameter, such as 40Cr, is selected and tempered to achieve a hardness of HRC35-40 before being used as the base material for the reinforcement rod 202. Circular positioning blocks 203 are welded at equal intervals onto the outer wall of the reinforcement rod 202. The positioning blocks 203 are made of the same material as the reinforcement rod 202 and are welded by argon arc welding. The weld height is ≥1mm, and flaw detection is required to ensure there are no defects such as incomplete welds or slag inclusions. After welding, the surface of the positioning blocks 203 is ground to ensure a smooth transition with the outer wall of the reinforcement rod 202. 06. Place the reinforcing rod 202 with the positioning block 203 assembled into a special forming mold. The shape of the mold cavity is completely matched with that of the nail core 2 and the punch 201. After the mold is preheated to 200-250℃, molten aluminum alloy liquid is injected into the cavity at a temperature controlled at 680-720℃ to ensure that the aluminum alloy fully fills the mold gap and wraps the reinforcing rod 202 and the positioning block 203. After the casting is completed, wait for the mold to cool naturally to room temperature and take out the blank. At this time, the punch 201 has been integrally formed with the casting process and forms a smooth transition with the main body of the nail core 2. The transition fillet radius is ≥2mm to reduce the risk of stress concentration. 07. Fix the cast nail core blank on a CNC machine tool and grind both ends to ensure a smooth surface. Then focus on punch 201: use a grinding wheel to grind its lower end until a frustum-shaped structure is formed. The taper is set according to the riveting requirements, usually 15°-30°, and the conical surface is polished to reduce the resistance when passing through the workpiece during riveting. During the grinding process, a micrometer should be used to measure the dimensions in real time to ensure that the diameter of punch 201 is larger than the diameter of the nail core 2 body and that there is no step at the transition between the two. 08. Machin an external thread on one end of the nail core 2. The thread specification is determined according to assembly requirements, such as M6 or M8. Use a rolling process to ensure that the thread profile is full and the accuracy reaches 6g level. After machining, place the nail core 2 into a special extrusion die for secondary extrusion to further optimize the transition structure between the punch 201 and the nail core 2 and enhance the overall strength. Finally, clean and deburr the surface of the nail core 2 to ensure that there are no sharp protrusions. 09. First, fit the retaining ring 301 onto the sleeve 1, ensuring that the upper end face of the retaining ring 301 is in close contact with the cap body 103 with a gap of ≤0.02mm, and fix it by interference fit; then, weld four auxiliary rods 302 in a ring array on the lower end face of the sleeve 1. The auxiliary rods 302 are made of high-strength aluminum alloy and are arranged in an inclined shape with an inclination angle of 30°-45°. The welding points need to be inspected for flaws to ensure the connection strength. 010. During assembly, the rivet core 2 is passed through the sleeve 1 from bottom to top, ensuring that the coaxiality error between the two is ≤0.05mm. After assembly, the entire rivet is galvanized: first, pickling is performed to remove rust and remove the surface oxide layer, then electroplating is used to form a uniform zinc layer thickness of 8-12μm, and finally passivation is performed to improve corrosion resistance. After galvanizing, the threads and mating surfaces need to be cleaned to ensure that the assembly performance is not affected.

[0032] The working principle of this embodiment: As one of the main load-bearing structures of the rivet, the socket 1 needs to possess good plasticity and strength. Based on its application scenarios, such as metal component connection and equipment assembly, and performance requirements, a cylindrical aluminum alloy tube with a suitable diameter is selected. Aluminum alloy is not only lightweight but also maintains stable mechanical properties during extrusion deformation, suitable for the plastic deformation requirements of the riveting process. After selection, the tube needs to undergo preliminary quality inspection, rejecting blanks with scratches, dents, or internal air bubbles to ensure the quality of the raw materials. High-strength tubing is used according to the design dimensions. A precision tube cutting machine cuts aluminum alloy tubes into blanks of specific lengths. During the cutting process, the cut must be kept perpendicular to the tube axis, with the error controlled within 0.1mm to avoid eccentricity problems in subsequent processing. After cutting, the blank is fixed on a CNC grinding machine, and both ends are roughly ground to remove burrs and oxide layers, achieving a flatness of 0.05mm / m, laying the foundation for subsequent processing. At this point, the initial sleeve 1 is formed. The roughly ground sleeve 1 is then fixed on a CNC lathe, where two rings are symmetrically machined on the inner wall. Auxiliary groove 102 is formed; the depth and width of auxiliary groove 102 must strictly follow the design parameters, and the bottom of the groove adopts a rounded transition to reduce stress concentration; subsequently, rectangular auxiliary holes 101 are machined in a ring array on the outer wall of the sleeve 1, and the position of the holes must be precisely aligned with the auxiliary groove 102 with a coaxiality error ≤0.03mm; during the machining process, a cooling system is used to continuously cool down the aluminum alloy to avoid deformation due to high temperature, ensuring the dimensional accuracy of auxiliary groove 102 and auxiliary holes 101, and providing a structural basis for smooth deformation during subsequent riveting. The process involves placing the sleeve 1, with its auxiliary groove 102 and auxiliary hole 101 machined, into a dedicated extrusion mold. A set pressure, adjusted according to the aluminum alloy grade, is applied using a hydraulic press, typically 50-80 MPa, to extrude the upper end of the sleeve 1 into a cap 103. During the extrusion process, the mold temperature and pressure changes must be monitored in real time to ensure that the cap 103 has a full shape, consistent dimensions, and a smooth transition with the main body of the sleeve 1, without cracks or wrinkles. After forming, the surface of the cap 103 is finely polished to achieve a roughness of Ra0.8μm; The core reinforcement structure of the nail core 2 is a reinforcing rod 202 made of high-hardness steel. High-quality alloy round steel with a suitable diameter, such as 40Cr, is selected and tempered to a hardness of HRC35-40 before being used as the base material for the reinforcing rod 202. Circular positioning blocks 203 are welded at equal intervals onto the outer wall of the reinforcing rod 202. The positioning blocks 203 are made of the same material as the reinforcing rod 202 and are welded using argon arc welding. The weld height is ≥1mm, and flaw detection is required to ensure there are no defects such as incomplete welds or slag inclusions. After welding, the surface of the positioning blocks 203 is ground to ensure a smooth transition with the outer wall of the reinforcing rod 202. The reinforcing rod 202 with the positioning blocks 203 assembled is then placed in a special... In the forming mold, the mold cavity perfectly matches the shape of the nail core 2 and the punch 201; after the mold is preheated to 200-250℃, molten aluminum alloy is injected into the cavity at a temperature controlled at 680-720℃ to ensure that the aluminum alloy fully fills the mold gaps and wraps the reinforcing rod 202 and the positioning block 203; after casting, the mold is allowed to cool naturally to room temperature, and the blank is removed. At this time, the punch 201 has been integrally formed during the casting process and forms a smooth transition with the main body of the nail core 2 with a fillet radius ≥2mm to reduce the risk of stress concentration; the cast nail core blank is fixed on a CNC machine tool, and the two end faces are ground to ensure a smooth surface; subsequently The key processing steps for punch 201 are as follows: Grind its lower end with a grinding wheel until a frustum-shaped structure is formed. The taper is set according to riveting requirements, typically 15°-30°. Polish the conical surface to reduce resistance when riveting through the workpiece. During grinding, use a micrometer to measure dimensions in real time to ensure that the diameter of punch 201 is larger than the diameter of the main body of nail core 2, and that there is no step at the transition between the two. Machine an external thread on the upper end of nail core 2. The thread specification is determined according to assembly requirements, such as M6 or M8. Use a rolling process to ensure a full thread profile and a precision of 6g. After machining, place nail core 2 into a special extrusion die for secondary extrusion to further optimize it. The transition structure between the punch 201 and the nail core 2 enhances the overall strength. Finally, the surface of the nail core 2 is cleaned and deburred to ensure there are no sharp protrusions. First, the retaining ring 301 is fitted onto the sleeve 1, ensuring a tight contact between the upper surface of the retaining ring 301 and the cap 103 with a gap ≤0.02mm, and fixed with an interference fit. Then, four auxiliary rods 302 are welded in a circular array on the lower surface of the sleeve 1. The auxiliary rods 302 are made of high-strength aluminum alloy and are arranged at an angle of 30°-45°. The welding points need to be inspected for flaws to ensure connection strength. During assembly, the nail core 2 passes through the sleeve 1 from bottom to top, ensuring that the coaxiality error between the two is ≤0.0.05mm; After assembly, the rivet is subjected to surface galvanizing: first, pickling is performed to remove rust and surface oxide layer, then electroplating is used to form a uniform zinc layer thickness of 8-12μm, and finally passivation is performed to improve corrosion resistance; after galvanizing, the threads and mating surfaces need to be cleaned to ensure that assembly performance is not affected; during use, the punch 201 and sleeve 1 are passed through the riveting object, and then the rivet core 2 is pulled. During pulling, the auxiliary holes 101 and auxiliary grooves 102 on the sleeve 1 deform; at the same time, the four auxiliary rods 302 pass through the riveting object, and under the pressure of the deformed part of the sleeve 1, the four auxiliary rods 302 bend to complete the auxiliary fixation of the riveting object.

Claims

1. An internal expansion fixing rivet, characterized in that, include: Sleeve (1); The sleeve (1) is a cylindrical tubular structure. A cap (103) is extruded at one end of the upper part of the sleeve (1). A nail core (2) is inserted into the sleeve (1). A punch (201) is extruded at one end of the lower part of the nail core (2). A thread is opened at one end of the upper part of the nail core (2). Two auxiliary grooves (102) are symmetrically opened on the inner wall of the sleeve (1). Both auxiliary grooves (102) are annular groove structures. The two auxiliary grooves (102) are guiding structures for the deformation of the sleeve (1).

2. The internal expansion fixing rivet according to claim 1, characterized in that, The outer wall of the sleeve (1) is provided with auxiliary holes (101) in a ring array. The auxiliary holes (101) are rectangular holes and are aligned with the auxiliary grooves (102).

3. The internal expansion fixing rivet according to claim 2, characterized in that, The diameter of the punch (201) is larger than the diameter of the nail core (2), and the punch (201) and the nail core (2) are subjected to a transition process.

4. The internal expansion fixing rivet according to claim 3, characterized in that, The nail core (2) is provided with a reinforcing rod (202), which is a cylindrical rod structure and is made of high-hardness steel.

5. The internal expansion fixing rivet according to claim 4, characterized in that, Positioning blocks (203) are welded at equal intervals on the reinforcing rod (202). The positioning blocks (203) are ring-shaped structures. The reinforcing rod (202) and the positioning blocks (203) are the reinforcing structures of the nail core (2).

6. The internal expansion fixing rivet according to claim 5, characterized in that, The sleeve (1) is fitted with a blocking component (3), which consists of a retaining ring (301) and an auxiliary rod (302). The retaining ring (301) is fitted on the sleeve (1). The retaining ring (301) has a ring structure and the upper end face of the retaining ring (301) is in contact with the cap body (103).

7. The internal expansion fixing rivet according to claim 6, characterized in that, The lower end face of the sleeve (1) is welded with four auxiliary rods (302) in a ring array, and the four auxiliary rods (302) are welded at an angle.

8. The internal expansion fixing rivet according to claim 7, characterized in that, The lower end of the punch (201) is polished, and after polishing, the lower end of the punch (201) has a frustum-shaped structure.

9. A method for manufacturing an internally expanding fixed rivet according to claim 8, characterized in that, Includes the following steps:

01. Sleeve (1) As one of the main load-bearing structures of rivets, it needs to have good plasticity and strength; according to its application scenario (such as metal component connection, equipment assembly, etc.) and performance requirements, select cylindrical aluminum alloy tubes with appropriate diameter - aluminum alloy material is not only lightweight, but also can maintain stable mechanical properties when extruded and deformed, which is suitable for the plastic deformation requirements in the riveting process; After selection, the pipes need to be preliminarily inspected to remove blanks with scratches, dents or air bubbles on the surface, so as to ensure the quality of raw materials.

02. According to the design dimensions, use a high-precision tube cutting machine to cut the aluminum alloy tube into blanks of a specific length; during the cutting process, the cut should be kept perpendicular to the tube axis, and the error should be controlled within 0.1mm to avoid eccentricity problems in subsequent processing; after the cutting is completed, fix the blank on a CNC grinding machine and rough grind both ends to remove burrs and oxide layers, so that the flatness of the end face reaches 0.05mm / m, laying the foundation for subsequent processing. At this time, the initial sleeve (1) is formed.

03. Fix the rough-ground sleeve (1) on a CNC lathe and machine two annular auxiliary grooves (102) symmetrically on the inner wall. The depth and width of the auxiliary grooves (102) must be strictly in accordance with the design parameters. The bottom of the groove is rounded to reduce stress concentration. Then, machine rectangular auxiliary holes (101) in an annular array on the outer wall of the sleeve (1). The position of the holes must be precisely aligned with the auxiliary grooves (102) (coaxiality error ≤ 0.03 mm). During the machining process, use a cooling system to continuously cool down to avoid deformation of the aluminum alloy due to high temperature, and ensure the dimensional accuracy of the auxiliary grooves (102) and auxiliary holes (101) to provide a structural basis for smooth deformation during subsequent riveting.

04. Place the sleeve (1) with the auxiliary groove (102) and auxiliary hole (101) into a special extrusion mold, and apply a set pressure (adjusted according to the aluminum alloy grade, usually 50-80MPa) through a hydraulic press to extrude one end of the sleeve (1) to form a cap (103); during the extrusion process, the temperature and pressure of the mold need to be monitored in real time to ensure that the shape of the cap (103) is full, the size is consistent, and the transition with the main body of the sleeve (1) is smooth, without cracks or wrinkles; after forming, the surface of the cap (103) is finely polished to make its roughness reach Ra0.8μm; 05. The core reinforcement structure of the nail core (2) is a reinforcement rod (202) made of high-hardness steel. High-quality alloy round steel (such as 40Cr) with a suitable diameter is selected and tempered (hardness reaches HRC35-40) as the base material of the reinforcement rod (202). Circular positioning blocks (203) are welded at equal intervals on the outer wall of the reinforcement rod (202). The positioning blocks (203) are made of the same material as the reinforcement rod (202) and are welded by argon arc welding. The weld height is ≥1mm and must be inspected for defects such as false welding and slag inclusion. After welding, the surface of the positioning blocks (203) is polished to make it smoothly transition with the outer wall of the reinforcement rod (202).

06. Place the reinforcing rod (202) with the positioning block (203) assembled into a special forming mold. The mold cavity is perfectly matched with the shape of the nail core (2) and the punch (201). After the mold is preheated to 200-250℃, inject molten aluminum alloy liquid into the cavity (temperature controlled at 680-720℃) to ensure that the aluminum alloy fully fills the mold gap and wraps the reinforcing rod (202) and the positioning block (203). After the casting is completed, wait for the mold to cool naturally to room temperature and take out the blank. At this time, the punch (201) has been integrally formed with the casting process and forms a smooth transition with the nail core (2) body (transition radius ≥ 2mm) to reduce the risk of stress concentration.

07. Fix the cast nail core blank on a CNC machine tool and grind both ends to ensure a smooth surface; then focus on the punch (201): use a grinding wheel to grind one end of it until a frustum-shaped structure is formed (the taper is set according to the riveting requirements, usually 15°-30°), and polish the conical surface to reduce the resistance when riveting through the workpiece; during the grinding process, a micrometer should be used to measure the dimensions in real time to ensure that the diameter of the punch (201) is greater than the diameter of the nail core (2) body, and there is no step at the transition between the two; 08. Machine an external thread on one end of the nail core (2). The thread specification is determined according to the assembly requirements (such as M6, M8, etc.). Use rolling process to ensure that the thread profile is full and the accuracy reaches 6g level. After processing, put the nail core (2) into a special extrusion mold for secondary extrusion to further optimize the transition structure between the punch (201) and the nail core (2) and enhance the overall strength. Finally, clean and deburr the surface of the nail core (2) to ensure that there are no sharp protrusions.

09. First, fit the retaining ring (301) onto the sleeve (1) so that the upper end face of the retaining ring (301) is in close contact with the cap body (103) (gap ≤ 0.02mm) and fix it by interference fit; then, weld four auxiliary rods (302) in a ring array on the lower end face of the sleeve (1). The auxiliary rods (302) are made of high-strength aluminum alloy and are arranged in an inclined manner (inclination angle 30°-45°). The welding points need to be inspected for flaws to ensure the connection strength.

010. During assembly, the rivet core (2) is passed through the sleeve (1) from bottom to top to ensure that the coaxiality error between the two is ≤0.05mm. After assembly, the rivet is galvanized: first pickling is performed to remove rust and remove the surface oxide layer, then a uniform zinc layer (thickness 8-12μm) is formed by electroplating, and finally passivation is performed to improve corrosion resistance. After galvanizing, the threads and mating surfaces need to be cleaned to ensure that the assembly performance is not affected.

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