A micro shape memory alloy wire driving assembly and a preparation method thereof

Abstract

This invention provides a miniature shape memory alloy wire drive component and its fabrication method, relating to the fields of microfabrication and shape memory alloy application technology. The fabrication method includes: spirally winding a shape memory alloy wire with a diameter of 0.03-0.08 mm onto the outer circumference of a miniature metal component to form at least one winding segment; applying an axial pre-tension force of 0.05-0.2 N to the alloy wire to maintain tension; and finally, using a pulsed laser to perform multi-point welding at the contact area between the winding segment and the component. This structure utilizes the geometric self-locking effect formed by winding, combined with the metallurgical bonding of laser welding, to achieve a dual connection of mechanical and electrical components. Examples show that the tensile strength of the weld joints of the drive component prepared by this method can reach 82% of the strength of the base material, and it exhibits excellent thermal cycling resistance and low contact resistance characteristics.

Description

Technical Field

[0001] This invention relates to the fields of microfabrication and shape memory alloy application technology, and in particular to a micro-shape memory alloy wire drive component and its preparation method. Background Technology

[0002] With the rapid development of microelectromechanical systems (MEMS), precision medical devices, and microrobotics, the demand for sub-millimeter-scale micro-actuators is increasing. Shape memory alloys (SMAs), due to their extremely high energy density, excellent biocompatibility, and simple actuation principle, have become one of the core materials in the field of micro-actuators. In the current technological environment of 2026, shape memory alloy wires have been widely used in various micro-actuators, where phase change contraction is induced by electrical heating, thereby outputting driving force.

[0003] However, in miniaturized applications (diameter <0.1mm), the connection process between shape memory alloy wires and metal electrodes or structural components has always been a technical bottleneck restricting their reliable application. Traditional connection methods typically involve laser direct spot welding of the shape memory alloy wire end to the metal component. Because the contact area between the micro-wire (typically 0.03-0.08mm in diameter) and the metal component is only a point contact, the connection strength is extremely low. According to experimental data, the weld strength of simple spot welding typically only reaches about 35% of the base material strength (approximately 420MPa), and stress concentration easily occurs at the weld point during high-frequency driving cycles, leading to early fatigue fracture and failing to meet the requirements for long-term stable operation. Some existing solutions use conductive adhesive for bonding. Although this method is simple, the adhesive is prone to aging, creep, or debonding under the thermal cycling environment (60-100℃) required for SMA operation. Experiments show that after 100 thermal cycles, the bonding strength of conductive adhesive decreases to below 300 MPa, and the contact resistance increases significantly (up to 5 Ω or more), leading to a decrease in driving efficiency or even failure. Some existing solutions use conductive adhesive for bonding. Although this method is simple, the adhesive is prone to aging, creep, or debonding under the thermal cycling (60-100℃) environment required for SMA operation.

[0004] In summary, existing micro-shape memory alloy wire connection technologies generally suffer from problems such as "low strength, poor thermal cycling performance, and unstable contact resistance." Especially in precision drive scenarios that require high reliability, how to achieve high-strength, low-resistance, and fatigue-resistant connections between shape memory alloy wires and metal components without damaging the micro-wires is a technical challenge that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a method for fabricating a micro-shape memory alloy wire driven component, specifically comprising: Winding: A shape memory alloy wire with a diameter of 0.03-0.08 mm is wound at least one turn around the outer circumference of the micro-metal component to form a wound segment. The number of winding turns is preferably 1-3 turns. The winding direction should be consistent with the contraction direction of the shape memory alloy wire when it is energized, so that the wound segment tightens further when it contracts, forming a self-locking effect; Applying a pre-tension force: Apply a pre-tension force to the wound shape memory alloy wire to maintain a tension of 0.05-0.2N in the cooled state. The magnitude of the pre-tension force is determined based on the diameter and material properties of the shape memory alloy wire, and is preferably 5%-20% of the tensile strength at break of the shape memory alloy wire. A pre-tension force below 0.05N will cause the wound section to loosen and fail to fit tightly; a pre-tension force above 0.2N may cause plastic deformation or even breakage of the wire, affecting its service life. Laser welding: A pulsed laser is used to weld at the contact points between the winding segment and the micro-metal component, forming laser weld points. The number of laser weld points is 2-4, evenly distributed along the circumference of the winding segment. Multi-point welding can disperse stress, avoid stress concentration, and improve fatigue life.

[0006] Preferably, the welding parameters of the pulsed laser are: pulse energy 0.1-0.8 mJ, pulse width 0.5-3 ms, and spot diameter 0.02-0.06 mm. The diameter of the laser weld is 0.03-0.08 mm, and the weld depth is 0.02-0.05 mm. These parameters need to be adjusted according to the wire diameter and component material to ensure the formation of a good weld nugget without damaging the wire.

[0007] Preferably, the ends of the shape memory alloy wire are laser-removed to remove the oxide layer before welding, exposing a fresh metal surface to improve welding quality.

[0008] Preferably, an inert gas is used for protection during the welding process. The inert gas is argon or helium, and the gas flow rate is 5-15 L / min to prevent oxidation of the welding area.

[0009] Preferably, the diameter of the micro metal component is 0.4-0.8 mm and the surface roughness Ra≤0.4 μm to ensure tight winding and welding quality.

[0010] Preferably, the shape memory alloy wire is a nickel-titanium based shape memory alloy with a phase transformation temperature of 60-100℃. The material of the micro-metal component can be selected from stainless steel, titanium alloy, copper alloy, or nickel alloy.

[0011] Preferably, the winding step is completed using an automated winding device, with the winding tension controlled at 0.05-0.2N and the winding speed at 5-20mm / s, to ensure uniform winding and consistent tension.

[0012] Preferably, after welding, a tensile test is performed on the weld joint, and the tensile strength of the weld joint is not less than 70% of the tensile strength of the shape memory alloy wire base material.

[0013] The present invention also provides a shape memory alloy drive component prepared by the above preparation method, comprising a micro metal component and a shape memory alloy wire fixedly connected thereto, wherein the shape memory alloy wire forms a reliable electrical and mechanical connection with the micro metal component by winding and laser welding.

[0014] Beneficial effects In this invention, a composite process of "spiral winding + laser spot welding" completely changes the force distribution mode of traditional micro-wire connections. Compared with simple laser spot welding or conductive adhesive bonding, this invention utilizes the self-locking effect formed by winding to convert the contraction force of the shape memory alloy wire (SMA) into radial clamping force, achieving dual mechanical and electrical locking. Example data shows that the tensile strength of the weld joint can reach 82% of the base material strength (approximately 980 MPa), and exhibits excellent stability in thermal cycling tests. Furthermore, by precisely controlling the pre-tensioning force of 0.05-0.2 N, both winding gaps and plastic deformation of the wire are eliminated. Combined with multi-point laser welding to disperse stress, this effectively solves the technical problem of easy detachment and wire breakage of micron-sized shape memory alloy wires under high-frequency drive, significantly improving the long-term reliability of the components. Attached Figure Description

[0015] 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.

[0016] The accompanying drawings described below are only related to some embodiments of the invention and are not intended to limit the invention.

[0017] In the attached diagram: Figure 1 A process flow diagram of the fabrication method of the micro-shape memory alloy wire drive assembly according to an embodiment of the present invention is shown.

[0018] Figure 2 A three-dimensional structural schematic diagram of a micro-shape memory alloy wire drive assembly according to an embodiment of the present invention is shown.

[0019] Figure 3 A schematic diagram of the solder joint distribution on a micro-shape memory alloy wire drive assembly according to an embodiment of the present invention is shown.

[0020] Figure 4 A schematic diagram of applying a pre-tension force after the shape memory alloy wire is wound according to an embodiment of the present invention is shown.

[0021] Figure 5A schematic diagram of the laser welding process after the shape memory alloy wire is wound according to an embodiment of the present invention is shown.

[0022] Figure 6 A schematic diagram of the clamping of a metal component by a first clamping fixture according to an embodiment of the present invention is shown.

[0023] Figure 7 A schematic diagram of a shape memory alloy wire assembled on a winding mechanism according to an embodiment of the present invention is shown.

[0024] Figure 8 A schematic diagram of the welded drive assembly assembled on the rotating part according to an embodiment of the present invention is shown.

[0025] List of main reference numerals 1. Drive component body; 101. Metal component; 102. Shape memory alloy wire; 1021. Winding section; 1022. Extension section; 103. Solder joint; 3. Drive unit; 301. Laser head; 302. First clamping fixture; 303. Winding mechanism; 4. Rotating part; 401. Cam body; 402. Rotating shaft. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] In this document, “illustrative” means “serving as an example, illustration or description”, and any illustration or implementation described herein as “illustrative” should not be construed as a more preferred or advantageous technical solution.

[0028] To keep the drawings concise, only the parts relevant to this application are shown schematically in each drawing, and they do not represent the actual structure of the product. In addition, to make the drawings concise and easy to understand, in some drawings, only one of the components with the same structure or function is shown schematically, or only one of them is labeled.

[0029] In this document, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple" refers to two or more; the terms "connected," "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0030] Example: Please refer to Figures 1 to 8 : This invention proposes a miniature shape memory alloy wire driving assembly, comprising: The main body of the drive component 1 is composed of shape memory alloy wire 102 and micro-metal components 101, wherein, for example... Figure 2 As shown, the shape memory alloy wire 102 forms a reliable electrical and mechanical connection with the micro-metal component 101 by winding and laser welding. Specifically, the shape memory alloy wire 102 is wound at least one turn on the outer circumference of the micro-metal component 101 to form a winding segment 1021, so that the winding segment 1021 and the micro-metal component 101 form a continuous contact surface, and an appropriate number of contact points are selected on this contact surface for laser welding. Preferably, the laser weld points 103 formed after laser welding are evenly distributed along the circumference of the winding segment 1021. By dispersing stress through multi-point welding, stress concentration is avoided and fatigue life is improved.

[0031] Regarding the aforementioned micro-shape memory alloy wire drive assembly, this invention also proposes a method for preparing the micro-shape memory alloy wire for use in the production of this drive assembly, such as... Figure 1 As shown, it includes the following steps: S1: Prepare materials Shape memory alloy wire 102 is used, which can generally be made of nickel-titanium alloy with a diameter of 0.05mm, a phase transformation temperature of 80℃, and a tensile strength of about 1200MPa.

[0032] Take the miniature metal component 101, which can generally be a 17-4PH stainless steel cylinder with a diameter of 0.5mm. The surface is finished to Ra0.2μm and cleaned and degreased at the same time.

[0033] S2: Entanglement Using a winding mechanism 303, shape memory alloy wire 102 is wound 1.5 turns around the outer circumference of the micro-metal component 101, such as... Figure 2 and Figure 7As shown. The winding direction is designed to be consistent with the shrinkage direction of the shape memory alloy wire 102 when energized—counterclockwise in this embodiment. The winding tension is controlled at 0.1N, and the winding speed is 10mm / s.

[0034] S3: Apply pre-tension force After winding is completed, a pre-tension force of 0.1N is applied to the extended section 1022 of the shape memory alloy wire 102, maintaining tension so that the wound section 1021 tightly adheres to the surface of the micro-metal component 101. Figure 4 As shown.

[0035] S4: Laser Welding Welding is performed using a laser head 301, with three weld points 103 uniformly welded circumferentially at the contact point between the winding section 1021 and the micro-metal component 101. Figure 3 As shown, the spacing between solder joints 103 is approximately 120°.

[0036] S5: Inspection After welding, the weld point 103 was visually inspected under a 40x microscope, and the drive assembly was subjected to a tensile test.

[0037] In step S4 above, the full name of the laser head 301 is a pulsed fiber laser, and the laser parameters used are as follows: Pulse energy: 0.3mJ; pulse width: 1.2ms; spot diameter: 0.03mm; wavelength: 1064nm; frequency: 10Hz.

[0038] In step S5 above, the tensile test results show that the tensile strength of weld 103 reaches 980 MPa, which is about 82% of the strength of the base material.

[0039] In another embodiment, to determine the influence of the winding segment 1021 on the strength of the solder joint 103, a comparative experiment with different winding turns was designed. Following the basic parameters of the above embodiment, the number of winding turns was varied for the comparative experiment, and the results are as follows:

[0040] Experiments show that wrapping 1.5 turns achieves the best connection strength, balancing contact area and accessibility of the solder joint 103.

[0041] In another embodiment, to determine the effect of laser pulse energy on the strength of weld joint 103, a comparative experiment with different laser parameters was designed. The number of winding turns was fixed at 1.5 turns, and the laser welding parameters were varied for comparison. The results are as follows:

[0042] Experiments show that a pulse energy of 0.3 mJ and a pulse width of 1.2 ms are the optimal parameter combination.

[0043] In another embodiment, to determine the effect of different pre-tension forces on the strength of weld joint 103, a comparative experiment with different pre-tension forces was designed, and the results are as follows:

[0044] Experiments show that the pre-tension force is preferably 5-15% of the tensile strength at break of the base material, corresponding to 0.06-0.18N in this example. When the pre-tension force is below 0.05N, the winding section 1021 shows obvious loosening, resulting in a decrease in strength after welding; when it is above 0.2N, the wire undergoes plastic deformation, affecting its service life.

[0045] Based on all the above embodiments, this embodiment demonstrates the application of the preparation method of the present invention to the mass production of micro-shape memory alloy wire 102. In mass production, a fully automated winding and welding integrated machine can be used, such as... Figure 5 , Figure 6 , Figure 7 As shown, the drive unit 3 of the device is displayed. The drive unit 3 specifically includes: a high-precision welding laser head 301, a first clamping fixture 302, and a winding mechanism 303. The laser head 301 has a vision positioning system, the first clamping fixture 302 can be rotated and positioned 360°, and the precision winding mechanism 303 integrates a tension sensor that can provide real-time feedback control of tension.

[0046] In this embodiment, the micro-metal component 101 is fixed by the first clamping fixture 302, and the precision winding mechanism 303 outputs the shape memory alloy wire 102. After the shape memory alloy wire 102 is wound around the micro-metal component 101 a certain number of times, the pre-tension force on the extension section 1022 of the shape memory alloy wire 102 is adjusted. Finally, the high-precision welding laser head 301 is used for welding, so that the shape memory alloy wire 102 is welded onto the micro-metal component 101. During the welding process, the first clamping fixture 302, in conjunction with the precision winding mechanism 303, rotates relative to the high-precision welding laser head 301 to adjust the spacing between multiple welding points 103.

[0047] In the above embodiments, the following process parameters are used: Winding speed: 15mm / s; winding tension: 0.1N, dynamic closed-loop control; number of winding turns: 1.5 turns; welding parameters: pulse energy 0.3mJ, pulse width 1.2ms, number of welding points: 3; production cycle: 8 seconds per piece, including loading and unloading.

[0048] In the above embodiment, the statistical results after mass production of 10,000 units are as follows: Solder joint strength: 950±50MPa, mean ± standard deviation; pass rate: 99.2%; contact resistance: <8mΩ.

[0049] To further verify the criticality of the parameter range in the above embodiments, boundary parameter experiments were conducted: 1. Lower limit of pre-tension force 0.05N: 1.5 turns of winding, post-weld strength 810MPa, which is 67.5% of the base material.

[0050] Although it is above 70%, it is close to the lower limit. When it is below 0.05N, the strength drops sharply to below 600MPa.

[0051] 2. Maximum pre-tension force: 0.2N; post-weld strength: 860MPa, which is 71.7% of the base material.

[0052] Although the requirements are met, slight plastic deformation marks appear on the surface of the wire. If the deformation exceeds 0.2N, the deformation intensifies and the strength decreases.

[0053] 3. Wire diameter lower limit 0.03mm: Using 0.03mm wire, with a pre-tension force of 0.05N, the weld strength can reach 75% of the base material.

[0054] 4. Maximum wire diameter 0.08mm: Using 0.08mm wire with a pre-tension force of 0.2N, the weld strength can reach 78% of the base material.

[0055] Experiments have shown that a pre-tension force range of 0.05N-0.2N and a wire diameter range of 0.03mm-0.08mm are necessary conditions for achieving excellent connection results.

[0056] To verify that the driving component and its preparation method in this invention have significantly superior technical effects compared to existing technologies, three comparative examples are provided for reference: Comparative Example 1: Simple laser spot welding without winding Using the same shape memory alloy wire and metal components, only the wire end is spot-welded to the surface of the component, without winding.

[0057] The weld strength is only 420MPa, which is 35% of the base material strength. Furthermore, during cyclic testing, stress concentration at the weld point led to fracture after 5000 cycles.

[0058] Comparative Example 2: Wrapping + Conductive Adhesive Bonding The same winding method is used, but conductive adhesive is used instead of laser welding.

[0059] The initial bonding strength is about 600 MPa, but after 100 thermal cycles at 80℃, the strength drops to 300 MPa and the contact resistance rises to 5 Ω, which cannot meet the requirements for long-term use.

[0060] Comparative Example 3: Simple crimping without wrapping or welding Microgroove pressing is used for fixing.

[0061] The initial strength was about 500 MPa, but it loosened after 500 thermal cycles and the contact resistance increased significantly.

[0062] The drive component prepared by the above method can be used as a basic unit in the application of the "A Micro Bistable Actuator Based on Shape Memory Alloy Wire Drive Component" submitted by the applicant on the same day.

[0063] For example, this embodiment provides an application method of the above-mentioned driving component, such as... Figure 8 As shown, in this embodiment, the main body 1 of the drive assembly is applied to a cam, a moving component. The cam is represented by a rotating part 4, which includes a cam body 401 and a rotating shaft 402. The rotating shaft 402 is provided on one end face of the cam body 401. The rotating part 4 can be rotatably connected to the frame of any actuator via the rotating shaft 402, allowing the cam body 401 to rotate around the rotating shaft 402 as the rotation center. The drive assembly is provided on the other end face of the cam body 401, and the extension section 1022 of the shape memory alloy wire 102 extends freely and is connected to a circuit board. When the shape memory alloy wire 102 is energized and contracts, it pulls the cam body 401 to rotate. The above description is merely a specific embodiment of this application. Under the above teachings of this application, those skilled in the art can make other improvements or modifications based on the above embodiments. Those skilled in the art should understand that the above specific description is only to better explain the purpose of this application, and the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for fabricating a micro-shape memory alloy wire drive component, characterized in that, Includes the following steps: A shape memory alloy wire (102) with a diameter of 0.03-0.08 mm is wound at least one turn on the outer circumference of the micro metal component (101) to form a wound segment (1021). A pre-stretching force is applied to the wound shape memory alloy wire (102) to maintain a tension of 0.05-0.2N in the cooled state; A pulsed laser is used to weld at the contact point between the winding segment and the micro-metal component to form laser weld points; the number of laser weld points is 2-4, and they are evenly distributed along the circumference of the winding segment.

2. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, In the winding step, the number of winding turns is 1-3 turns.

3. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, In the winding step, the winding direction should be consistent with the shrinkage direction of the shape memory alloy wire (102) when it is energized and shrinks, so that the winding section (1021) is further tightened when shrinking.

4. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, The pre-tension force is determined based on the diameter and material properties of the shape memory alloy wire (102), and the magnitude of the pre-tension force is 5%-20% of the tensile strength at break of the shape memory alloy wire (102).

5. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, During the welding process, the welding parameters of the pulsed laser are: pulse energy 0.1-0.8mJ, pulse width 0.5-3ms, and spot diameter 0.02-0.06mm.

6. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, The diameter of the laser weld point (103) is 0.03-0.08 mm, and the weld point depth is 0.02-0.05 mm.

7. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, The micro-metal component (101) has a diameter of 0.4-0.8 mm and a surface roughness Ra≤0.4 μm.

8. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, The shape memory alloy wire (102) is a nickel-titanium based shape memory alloy with a phase transformation temperature of 60-100℃.

9. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, The welding process is protected by an inert gas, which is either argon or helium, and the gas flow rate is 5-15 L / min.

10. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, The material of the micro-metal component (101) is selected from stainless steel, titanium alloy, copper alloy or nickel alloy.

11. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, Before the welding step, the end of the shape memory alloy wire (102) is subjected to laser stripping of the oxide layer to expose the fresh metal surface.

12. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, The winding step is completed by a winding mechanism (303), with the winding tension controlled at 0.05-0.2N and the winding speed at 5-20mm / s.

13. The method for preparing a micro-shape memory alloy wire driving component according to claim 1, characterized in that, After the welding step, a tensile test is performed on the weld joint, and the tensile strength of the weld joint is not less than 70% of the tensile strength of the shape memory alloy wire (102) base material.

14. A micro-shape memory alloy wire drive assembly, prepared according to the preparation method of any one of claims 1-13, characterized in that, include: The micro-metal component (101) and the shape memory alloy wire (102) are wound around the outer circumference of the micro-metal component (101) at least once and are fixedly connected to the micro-metal component (101) by at least two laser welding points (103) distributed along the circumference.

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