A Laser Skip Welding Method for the Stator Winding of a Flat Copper Wire Motor

Abstract

The present invention belongs to the technical field of laser welding, and specifically discloses a laser skip welding method for a flat copper wire motor stator winding. The laser skip welding method for the flat copper wire motor stator winding includes the following steps S1: pre-treating the flat copper wire and fixing the flat copper wire to be processed by a fixture; S2: using a vision system to locate the welding positions of the flat copper wire; S3: the laser welding head welds the flat copper wire along a specified welding trajectory by combining a central beam and an annular beam. In practical application, the laser skip welding process of the present invention effectively solves the welding problem caused by the fitting gap at the welding points of the flat copper wire motor winding through the discontinuous welding trajectory, avoids the problem that the laser directly penetrates through the gap to break through the insulating paint film below, reduces the risk of motor insulation failure, and ensures the performance and service life of the motor; the welding efficiency is improved by accurately positioning the welding points through the vision system.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser welding, and specifically discloses a laser skip welding method for a stator winding of a flat copper wire motor. Background Art

[0002] In the field of new energy vehicle drive motors, with the continuous increase in the demand for power density, due to its unique flat copper wire structure, the stator of a flat copper wire motor can provide higher power while reducing the volume, and is gradually becoming a new trend in the industry development. During the manufacturing process of the stator of a flat copper wire motor, the quality of the winding solder joints is directly affected by the incoming material state, especially the mating gap between the copper wires. When there is no gap, by adopting a continuous laser welding track, effective focusing of laser energy can be achieved, so as to form a firm weld at the copper wire joint, ensuring the smoothness of current flow and the welding strength. However, once a gap appears, the continuous welding track will cause the laser to penetrate the gap, damaging the insulating coating below, leading to a decline in the insulation performance of the motor, or even failure.

[0003] Currently, the automated production lines of the stator of a flat copper wire motor generally adopt a quick clamping tooling, which locks multiple solder joints at one time through two rotating clamping disks, aiming to improve the welding rhythm. Although this method can clamp 150 to 300 solder joints at the same time, it is difficult to completely eliminate the mating gap between the copper wires. Therefore, in actual production, the application of the continuous laser welding track is restricted and its advantages cannot be fully utilized, which constitutes a key problem to be solved urgently in the prior art.

[0004] For a laser welding method and a laser welding method for multi-layer weld seams with the patent application number CN201611088687.4, the laser welding method includes: Step 1: Divide the weld seam area of the parts to be welded into blocks. The first welding block includes multiple welding segments, and the second welding block includes multiple welding segments; Step 2: Select the middle of the weld seam area as the starting point, and perform skip welding starting from the welding segment in the middle of the weld seam area. The skip welding path is to weld the same welding block as this welding segment, and start from this welding segment to perform spiral welding until the welding reaches the last welding block of this welding block; Step 3: Use the welding segment adjacent to the welding segment used as the starting point in Step 2 as the starting point to perform skip welding. The skip welding path is to weld the same welding block as this welding segment, and start from this welding segment to perform spiral welding until the welding reaches the last welding block of this welding block. The above method cannot accurately position the welding points, and errors may occur during welding, causing damage to the workpiece. Therefore, it is urgent for those skilled in the art to solve the above technical problems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that in the above-mentioned prior art, the application of the continuous laser welding track is restricted, its advantages cannot be fully utilized, and it is difficult to accurately position the solder joints.

[0006] To solve the above technical problem, the technical solution adopted by the present invention is as follows:

[0007] A laser skip welding method for a flat copper wire motor stator winding, the laser skip welding method for the flat copper wire motor stator winding includes the following steps. S1: Pretreat the flat copper wire and fix the flat copper wire to be processed by a fixture; S2: Use a vision system to position the solder joint position of the flat copper wire; S3: The laser welding head welds the flat copper wire along a specified welding track by combining a central beam and an annular beam. In step S1, before welding, the insulating paint film on the surface of the copper wire is removed, and the two copper wires to be processed are aligned, clamped and trimmed flat by a fixture, and the gap between the two copper wires needs to be kept below 0.5 mm; in step S2, the vision system includes a detection head, a processing unit and a connecting shaft; the detection head and the laser welding head are mounted on the connecting shaft, the detection head takes pictures of the flat copper wire to be processed driven by the connecting shaft, the image information obtained by the detection head is transmitted to the processing unit, the processing unit locates the solder joint of the flat copper wire to be processed according to the image information, and the connecting shaft drives the laser welding head to move to the solder joint position of the flat copper wire to be processed under the control of the processing unit; in step S3, the welding track includes a first welding track, a second welding track and a third welding track; the first welding track and the second welding track are scanned on the upper and lower copper wires successively, the upper and lower copper wires are melted under the laser irradiation and form spherical molten pools, the size of the formed molten pools is larger than the size of the flat copper wire substrate, and the parts exceeding the substrate will be fused with each other, thus filling the gap; after the gap is filled, use the third welding track to scan across the gap on the two copper wires to further expand the formed spherical molten pools and improve the shape of the spheres.

[0008] Remove the insulating paint film on the surface of the copper wire before welding to ensure a sufficient length of bare copper to prevent the insulating paint from affecting the welding quality during the welding process and to prevent damage to the paint film caused by welding heat when the length of the bare copper is too short. Using a fixture to align and clamp the copper wire can ensure the relative position of the copper wire is accurate during welding, avoiding poor welding caused by position deviation during the welding process, ensuring the reliability and consistency of the solder joints. Cutting the end of the copper wire flat makes the welding surface flat, which is conducive to the uniform coverage of the laser spot, ensuring the consistency of the welding penetration and width, thereby improving the strength and quality of the welded joint. Controlling the gap between the copper wires below 0.5 mm can ensure the applicability of the laser skip welding process because too large a gap may cause the laser to be unable to effectively melt the copper wire or the molten pool generated by melting cannot be fully fused, affecting the welding effect. Proper gap control helps the laser energy to be evenly distributed between the copper wires, forming a stable molten pool and ensuring the smooth progress of the welding process. Through the first welding track and the second welding track, independent spherical molten pools are formed on the end faces of the two copper wires respectively. After the molten pools are fused, the third welding track is used to further expand the molten pool, increasing the penetration and width of the solder joint, thereby significantly improving the mechanical strength and electrical conductivity of the solder joint. When there is a gap between the two copper wires, the traditional continuous welding track may not be able to effectively weld or even damage the insulating layer. The segmented welding track can avoid the gap, first form a molten pool on the end face of each copper wire, and then fill the gap through the third welding track, solving the problem of gap welding. The first and second welding tracks form a preliminary molten pool. The third welding track not only fills the gap but also further optimizes the shape of the molten pool to make it more round and full, improving the aesthetics of the solder joint and the quality of the weld seam. Due to the intermittency of the welding track, the application of high temperature at a single position for a long time is avoided, thereby reducing the heat affected zone and reducing the thermal damage to the surrounding materials during the welding process, which is beneficial to maintaining the original performance of the flat copper wire motor stator. By precisely controlling the laser power and scanning speed and combining the three-segment welding track, the welding process can be completed quickly. Compared with traditional continuous welding, this method improves production efficiency and is suitable for large-scale automated production. Using a standardized multi-segment welding track can ensure consistent welding effects on different solder joints, which is crucial for maintaining the stability of product quality in mass production.

[0009] Further, when welding the flat copper wire to be processed, the first welding track, the second welding track, and the third welding track are all square tracks. The specifications of the first welding track and the second welding track are 1.8*0.8 mm, and the specification of the third welding track is 1.8*2 mm. The third welding track is located between the first welding track and the second welding track. The laser welding head welds in the order of the first welding track, the second welding track, and the third welding track. When welding, the center power of the laser welding head is set to 3500 - 4000 w, and the outer ring power is set to 1500 - 2000 w.

[0010] By using square welding tracks of specific sizes, the shape and size of the molten pool can be precisely controlled to ensure that the penetration depth and width of the welding area reach the optimum, thereby improving the strength and electrical performance of the solder joints. The first welding track and the second welding track are smaller in size and are used to form the initial molten pool, while the third welding track is larger in size and is used to expand the molten pool and fill the gap. This design can adapt to different welding requirements, especially in the presence of gaps, effectively filling the gaps and optimizing the shape of the molten pool. The center power and outer ring power of the laser welding head are set at 3500 - 4000 watts and 1500 - 2000 watts respectively. This power distribution can concentrate heat at the welding point, reduce the thermal impact on the surrounding materials, thereby reducing thermal deformation and thermal stress and improving the overall quality of the welded parts. Adopting segmented welding tracks, with the size and power of each track optimized, the welding can be completed in a shorter time, improving productivity while maintaining welding quality.

[0011] Further, when welding the first welding track and the second welding track, the scanning speed of the laser welding head is 500 mm / s. When welding the third welding track, the scanning speed of the laser welding head is 800 mm / s.

[0012] During the welding process of the first welding track and the second welding track, a lower scanning speed (500 mm / s) allows the laser to stay on the end face of the copper wire for a longer time, which helps to form a more sufficient spherical molten pool, ensuring that the size of the molten pool exceeds that of the copper wire substrate, thus forming good fusion at the gap. When welding the third welding track, increasing the scanning speed to 800 mm / s can accelerate the welding process, improve production efficiency, and still ensure sufficient stirring of the molten pool, optimize the shape of the molten pool, and improve the appearance and structural strength of the solder joint. Different scanning speeds combined with specific laser powers can more precisely control the heat input in each welding stage, help reduce the heat-affected zone, avoid material property degradation caused by overheating, and also help control welding deformation. In the third welding track, a higher scanning speed helps to fill the gap while reducing local overheating and avoiding cracks formed due to too rapid cooling of the molten pool, thereby enhancing the strength and reliability of the solder joint.

[0013] Furthermore, the first welding track, the second welding track, and the third welding track can also be elliptical or racetrack-shaped.

[0014] Elliptical or racetrack-shaped tracks can distribute laser energy more evenly, helping to form a more uniform molten pool, avoiding the sharp edges or irregularities that may be caused by square tracks, thus improving the uniformity of the solder joint. Non-square tracks can better control the distribution of heat input, reduce the range of the heat-affected zone, and reduce the thermal shock to the surrounding materials, helping to maintain the original properties and structural integrity of the flat copper wire motor stator winding. Elliptical or racetrack-shaped tracks can adapt to different welding requirements. For example, under specific conditions, such tracks can better fill irregular gaps, improve the tightness and strength of the weld. Non-linear tracks help to form a more stable molten pool during the welding process, promote the full diffusion and crystallization of metal atoms, thereby enhancing the microstructure of the solder joint and improving the mechanical strength and electrical conductivity of the solder joint. In some cases, elliptical or racetrack-shaped tracks can reduce the start and stop times of the laser head, improve the continuity of welding, thus improving welding efficiency and accelerating the production rhythm.

[0015] Furthermore, the laser welding head uses a laser with a central beam having a core diameter of 50 μm and a maximum power of 4000 w, and an outer ring beam having a core diameter of 150 μm and a maximum power of 2000 w, and the laser wavelength is 1030 - 1090 nm.

[0016] The core diameter of the central beam is small and the power is high, which means that the energy density per unit area is extremely high, capable of quickly heating and melting the copper wire to form a molten pool, ensuring the depth and strength of the welding point. The use of the outer ring beam can help expand the keyhole opening formed by the central beam. A keyhole is a small hole formed due to the melting and evaporation of materials caused by the input of laser energy during the laser welding process. Expanding the keyhole opening is beneficial for the discharge of metal vapor, reducing the pressure inside the molten pool, thereby effectively suppressing the generation of spatter. Spatter refers to the phenomenon where molten metal particles splash out from the molten pool. It not only affects the appearance of the weld seam but may also reduce the welding quality, causing defects such as lack of fusion or porosity. The laser wavelength of 1030 - 1090 nm is efficiently absorbed by copper materials, which means that more laser energy can be converted into heat energy, promoting the melting of materials and improving the welding efficiency. By finely adjusting the power of the central beam and the outer ring beam, and using a laser with a specific wavelength, precise control of the welding process can be achieved, reducing welding defects such as cracks and pores, thereby improving the welding quality.

[0017] The present invention has the following beneficial effects: Through the skip welding process, the welding problem caused by the gap between flat copper wires can be effectively solved, ensuring the strength of the solder joint and the reliability of the electrical connection. The introduction of the vision system improves the positioning accuracy of the solder joints of the workpieces to be welded. Combining with efficient laser welding and the three - segment welding trajectory design not only fills the gap but also improves the shape of the solder joint, forming a round and full solder joint appearance, increasing the weld area and the penetration depth. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the method flow of the present invention.

[0019] Figure 2 It is a schematic diagram of the placement of copper wires in an embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram of the laser form in an embodiment of the present invention.

[0021] Figure 4 It is a schematic diagram of the welding trajectory in an embodiment of the present invention.

[0022] Figure 5 It is a schematic diagram of the welding state in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be further described in detail below in conjunction with the drawings and specific preferred embodiments.

[0024] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "left side", "right side", "upper part", "lower part", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second", etc. do not represent the importance of components, so it cannot be understood as a limitation to the present invention. The specific dimensions adopted in this embodiment are only for illustrating the technical solution by way of example and do not limit the protection scope of the present invention.

[0025] Referring to Figure 1 , Figure 2 , Figure 3 and Figure 4 , it can be known that for a laser skip welding method of a flat copper wire motor stator winding, first, the flat copper wire is pre-treated and the flat copper wire to be processed is fixed by a fixture; then a vision system is used to locate the welding positions of the flat copper wire; finally, the laser welding head welds the flat copper wire along the specified welding trajectory by combining a central beam and an annular beam.

[0026] In one embodiment, before welding, first remove 8 mm of the insulating paint film of the copper wire to be processed, and use a fixture to align, clamp and cut flat the two copper wires to be welded. The gap between the two copper wires needs to be no more than 0.5 mm to prevent the gap from being too large to use the skip welding trajectory for welding. The connecting shaft moves the laser welding head to the welding position. The detection head of the vision system takes pictures of all the welding positions in turn and transmits them to the processing unit for analysis and processing to give the welding coordinates, and guides the scanning laser welding head to weld all the welding points in turn. Use a laser welding head of LS30.125399 specification, and a laser with a central beam of core diameter 50 μm and maximum power 4000 w and an outer ring beam of core diameter 150 μm and maximum power 2000 w. The wavelength of the laser is 1030 - 1090 nm. The copper wire to be processed is welded using a discontinuous laser scanning trajectory. The welding trajectory includes a first welding trajectory, a second welding trajectory and a third welding trajectory. The welding trajectory can be square, elliptical and racetrack-shaped. In the square welding trajectory, when the laser welding head is welding, the sizes of the first welding trajectory and the second welding trajectory are both 1.8 * 0.8 mm, the scanning speed of the laser welding head is 500 mm / s, the size of the third welding trajectory is 1.8 * 2 mm, and the scanning speed of the laser welding head is 800 mm / s.

[0027] Referring to Figure 5 , it can be known that the focused laser beam is scanned in sequence along the first welding trajectory, the second welding trajectory and the third welding trajectory according to the set power. The central power is set to a maximum of 3500 - 4000 w, and the outer ring power is set to a maximum of 1500 - 2000 w;

[0028] During welding, the first and second welding tracks are scanned successively on the upper and lower copper wires. The upper and lower copper wires melt under the laser irradiation and form a spherical molten pool. The size of the formed molten pool is larger than the size of the copper wire substrate. The part that exceeds the substrate will fuse together, thus filling the gap. After the gap is filled, the third welding track is used to scan across the gap on the two copper wires, further expanding the formed spherical molten pool and improving the shape of the sphere.

[0029] Furthermore, the third weld trajectory is designed to focus primarily on the mating surface of the two copper wires. Here, the laser energy is precisely directed to concentrate the melting of the copper in this area. Unlike the first and second weld trajectories, the third weld trajectory aims to further expand and deepen the initial molten pool formed by the first two trajectories. This is because when the laser beam directly impacts the mating surface of the two copper wires, its energy density is sufficient to generate sufficient heat input in a short period of time, causing the copper to melt rapidly and forming a deeper molten pool. This increased molten pool depth means greater penetration of the weld, thereby enhancing its mechanical strength and ensuring the reliability of the flat copper wire motor stator winding under current cycling and mechanical stress. The laser energy is concentrated on the mating surface of the copper wires in the third weld trajectory, increasing both the molten pool depth and its width, i.e., the weld area. This increased weld area creates a wider contact interface between the two copper wires, providing a larger current conduction path, reducing resistance, and improving electrical performance. At the same time, the wider weld area also helps disperse stress, reducing stress concentration at the weld point, further improving the durability of the weld and the stability of the overall structure. The optimized design of the third welding trajectory is also reflected in its improved welding efficiency. By adopting appropriate laser power and scanning speed, the third welding trajectory can reduce welding time, speed up production cycle, and improve overall production efficiency while ensuring the depth of the molten pool and the weld area. In addition, the precise control of the third welding trajectory helps to reduce the heat-affected zone, avoid material degradation caused by overheating, and ensure the integrity and functionality of the weld area and the surrounding structure.

[0030] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention.

Claims

1. A laser skip welding method for a flat copper wire motor stator winding, characterized in that: The laser skip welding method for the flat copper wire motor stator winding includes the following steps. S1: Pre-treat the flat copper wire and fix the flat copper wire to be processed with a fixture. S2: Use a vision system to locate the welding position of the flat copper wire. S3: The laser welding head welds the flat copper wire along the specified welding trajectory by combining a central beam and an annular beam. In step S1, before welding, remove the insulating paint film on the surface of the copper wire, use a fixture to align, clamp and cut flat two copper wires to be processed. The gap between the two copper wires needs to be kept below 0.5 mm. In step S2, the vision system includes a detection head, a processing unit and a connecting shaft. The detection head and the laser welding head are mounted on the connecting shaft. The detection head takes pictures of the flat copper wire to be processed driven by the connecting shaft. The image information obtained by the detection head is transmitted to the processing unit. The processing unit locates the welding point of the flat copper wire to be processed according to the image information. The connecting shaft drives the laser welding head to move to the welding point position of the flat copper wire to be processed under the control of the processing unit. In step S3, the welding trajectory includes a first welding trajectory, a second welding trajectory and a third welding trajectory. The first welding trajectory and the second welding trajectory are scanned on the upper and lower copper wires successively. The upper and lower copper wires melt under the laser irradiation and form spherical molten pools. The size of the formed molten pool is larger than the size of the flat copper wire substrate. The part exceeding the substrate will fuse with each other, thus filling the gap. After the gap is filled, use the third welding trajectory to scan across the gap on the two copper wires to further expand the formed spherical molten pool and improve the shape of the sphere. The laser energy acts concentratedly on the copper wire joint surface in the third welding trajectory. When welding the first welding trajectory and the second welding trajectory, the scanning speed of the laser welding head is 500 mm / s. When welding the third welding trajectory, the scanning speed of the laser welding head is 800 mm / s. When welding the flat copper wire to be processed, the first welding trajectory, the second welding trajectory and the third welding trajectory are all square trajectories. The specifications of the first welding trajectory and the second welding trajectory are 1.8 * 0.8 mm, and the specification of the third welding trajectory is 1.8 * 2 mm. The third welding trajectory is located between the first welding trajectory and the second welding trajectory. The laser welding head welds in the order of the first welding trajectory, the second welding trajectory and the third welding trajectory. When welding, the central power of the laser welding head is set to 3500 - 4000 w, and the outer ring power is set to 1500 - 2000 w.

2. The laser skip welding method for the flat copper wire motor stator winding according to claim 1, wherein: The laser welding head uses a laser with a central beam having a core diameter of 50 μm and a maximum power of 4000 w and an outer ring beam having a core diameter of 150 μm and a maximum power of 2000 w. The laser wavelength is 1030 - 1090 nm.

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