Processing method of stator assembly, brushless direct current motor and fan

Abstract

The present disclosure relates to the technical field of motor processing, and provides a processing method of a stator assembly, a brushless direct current motor and a fan. The processing method comprises the following steps: providing a stator core with stator teeth; embedding the stator core into an injection mold as an insert, and independently positioning in the radial and axial directions; injecting insulating material to form an insulating frame by one-time injection molding, so that the frame part covers the outer periphery of the stator teeth, and the tooth top surface of the stator teeth is exposed; obtaining an integrated combined structure after demolding; winding a coil winding on the frame part, and the winding does not cross the tooth top surface. The method simplifies the processing and assembly process, improves the bonding strength and positioning accuracy of the frame and the core, and is beneficial to improving the performance and reliability of the motor.

Description

Technical Field

[0001] This disclosure relates to the field of motor processing technology, and more specifically, to a method for processing a stator assembly, a brushless DC motor, and a fan. Background Technology

[0002] Brushless DC motors typically consist of a stator assembly and a rotor assembly. The stator assembly generally includes a stator core, an upper winding frame and a lower winding frame respectively disposed on both sides of the stator core along its axial direction, and windings wound on the stator core. The upper and lower winding frames are used to isolate the coil windings from the stator core and to support and limit the coil windings.

[0003] In existing technology, the upper and lower winding frames are typically formed separately and then assembled from both sides of the stator core. However, since the upper and lower winding frames are independent parts, this increases the forming, inspection, and assembly processes, and misalignment, warping, or unstable fixing can easily occur during assembly. Furthermore, during the subsequent coil winding process, the winding frames may move relative to the stator core under winding tension, affecting the normal arrangement of the coil windings.

[0004] Therefore, how to simplify the processing and assembly of stator components and improve the positioning stability between the wire frame and the stator core is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method for processing a stator assembly, a brushless DC motor, and a fan, which solves the problems mentioned in the background art.

[0006] According to a first aspect, this disclosure provides a method for processing a stator assembly, comprising: Step S1, providing a stator core, the stator core including a stator ring and a plurality of stator teeth spaced circumferentially along the outer wall of the stator ring; Step S2: Install the stator core as an insert into the injection mold, and perform independent radial and axial positioning of the stator core. Step S3: Insulating material is injected into the injection mold to form an insulating wire frame in one injection molding process; wherein, the insulating wire frame includes a wire frame body and a plurality of wire frame portions distributed circumferentially along the wire frame body, the stator ring is located in the wire frame body, the wire frame portions cover the outer peripheral wall of the stator teeth, and the tooth top surface of the stator teeth is exposed to the wire frame portions; Step S4: After cooling and demolding, an integrated composite structure including the stator core and the insulating wire frame is obtained; Step S5: After obtaining the integrated assembly structure, a coil winding is formed by winding wire around each of the wire frame parts. During the winding process, the coil winding is wound around the outer surface of the wire frame part and does not cross the tooth top surface, thus obtaining a stator assembly having the stator core, the insulating wire frame and the coil winding.

[0007] In an exemplary embodiment of this disclosure, the injection mold includes a positioning mandrel and a clamping block. In step S2, the positioning mandrel radially positions the inner hole of the stator ring, and the clamping block abuts against the axial end face of the stator core for axial positioning, thereby maintaining the stator core in a fixed position during injection molding. Preferably, the positioning references for radial positioning and axial positioning are independent of each other and not related to each other, to avoid over-constraint during positioning and ensure the accuracy and repeatability of positioning.

[0008] In an exemplary embodiment of this disclosure, in step S2, the stator core placed in the injection mold is a stator core that has undergone degreasing, drying, and preheating treatment. The stator core is positioned within 40-120 seconds after preheating, allowing it to be injection molded in a preheated state. Preferably, the preheating temperature range is 80°C to 150°C, specifically determined based on the fluidity of the insulating material and the dimensions of the stator core.

[0009] In one exemplary embodiment of this disclosure, in step S3, the insulating material is a thermoplastic engineering plastic, the injection temperature is 260℃~320℃, the injection pressure is 80MPa~150MPa, and the holding time is 3s~8s. This process parameter window ensures that the molten plastic fully fills the mold cavity, while avoiding thermal deformation of the stator core due to excessive temperature or pressure.

[0010] In an exemplary embodiment of this disclosure, in step S4, during demolding, the axial positioning of the stator core is first released, allowing the integrated structure formed by the stator core and the insulating wire frame to move synchronously. Then, the radial positioning of the stator core is released, and the positioning mandrel is withdrawn along the axial direction of the stator core to complete demolding. This demolding sequence can effectively prevent cracks or warping deformation of the injection molded part due to uneven force during demolding.

[0011] In an exemplary embodiment of this disclosure, in step S5, coil windings are sequentially formed by alternating winding of adjacent wire frames. After each layer of winding is completed, the coil windings are pressed and shaped using the tooth tip surface as an axial reference before proceeding to the next layer of winding. Preferably, the winding tension is controlled between 1.5N and 4.5N, and the winding speed is controlled between 1500rpm and 3000rpm to ensure that the coils are tightly arranged without damaging the insulation layer.

[0012] According to a second aspect, this disclosure provides a brushless DC motor, including a motor drive board, a stator assembly, and a rotor assembly sleeved outside the stator assembly. The stator assembly includes a stator core, an insulating wire frame injection molded on the stator core, and a coil winding wound on the wire frame portion of the insulating wire frame. The stator assembly is manufactured using the processing method described in the first aspect. The stator core is fitted with a mounting tube for mounting the brushless DC motor, and the rotor assembly is fitted with two bearings arranged at intervals, which are respectively sleeved with the mounting tube.

[0013] In one exemplary embodiment of this disclosure, the rotor assembly includes a rotor housing, within which a magnetically conductive shell is disposed, and a permanent magnet is installed within the magnetically conductive shell. The stator teeth have a gap between their top surfaces and the permanent magnet. Preferably, the width of the air gap ranges from 0.3 mm to 0.8 mm.

[0014] In one exemplary embodiment of this disclosure, one of the bearings abuts against the end of the insulating wire frame, the mounting tube is fitted with a retaining ring, the rotor assembly is provided with a spring plate, and the other bearing abuts between the retaining ring and the spring plate.

[0015] In one exemplary embodiment of this disclosure, the mounting tube has a wire-passing hole corresponding to the motor drive board, the stator ring of the stator core has a positioning groove, and the outer wall of the mounting tube has a positioning protrusion that is inserted into and positioned with the positioning groove. The length of the positioning protrusion is less than the groove length of the positioning groove.

[0016] In an exemplary embodiment of this disclosure, the outer wall of the mounting tube is provided with a limiting protrusion arranged in the same direction as the positioning protrusion, the limiting protrusion is provided with a limiting surface that abuts against the end face of the stator ring, and the width of the limiting protrusion is greater than the width of the positioning protrusion.

[0017] In one exemplary embodiment of this disclosure, the wire frame portion is provided with a protrusion, and one end of the insulated wire frame near the motor drive plate is provided with a hook that engages with the motor drive plate. One side of the motor drive plate abuts against the protrusion, and the other side of the motor drive plate engages with the hook.

[0018] According to a third aspect, this disclosure provides a fan, including a fan body and a brushless DC motor as described in the second aspect, the brushless DC motor being connected to the fan body, and fan blades being mounted on the rotor assembly.

[0019] As can be seen from the above technical solutions, the stator assembly processing method, brushless DC motor, and fan in the exemplary embodiments of this disclosure have at least the following advantages and positive effects: 1. By using the stator core as an insert and implementing independent radial and axial positioning, the position of the core is accurately fixed during injection molding, avoiding displacement.

[0020] 2. The insulation wire frame is formed by injection molding in one step, eliminating the need for independent molding and secondary assembly processes, simplifying the processing flow and reducing processing costs.

[0021] 3. Because the wire frame covers the stator teeth and the tooth top surface is exposed, the insulation performance of the insulated wire frame is guaranteed, and a precise axial reference is provided for subsequent winding. This prevents the winding from crossing the tooth top surface, avoiding the risk of short circuits and disordered arrangement caused by crossing wires, improving the winding quality and consistency, and thus improving the stability of motor operation.

[0022] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 A flowchart illustrating a method for fabricating a stator assembly according to an embodiment of the present disclosure is shown; Figure 2 A three-dimensional structural schematic diagram of a brushless DC motor according to an embodiment of the present disclosure is shown; Figure 3 A side view of a brushless DC motor according to an embodiment of the present disclosure is shown; Figure 4 It shows Figure 3 A schematic diagram of the AA cross-sectional structure; Figure 5 An exploded structural diagram of a brushless DC motor according to an embodiment of the present disclosure is shown; Figure 6 A partial exploded view of the stator assembly in a brushless DC motor according to an embodiment of the present disclosure is shown. Figure 7 An exploded structural diagram of the rotor assembly in a brushless DC motor according to an embodiment of the present disclosure is shown. Figure 8 A schematic diagram of the mounting tube in a brushless DC motor according to an embodiment of the present disclosure is shown.

[0024] Illustration: 100. Motor drive board; 200. Stator assembly; 210. Stator core; 211. Stator ring; 2111. Positioning groove; 212. Stator tooth; 2121. Tooth top surface; 220. Insulating wire frame; 221. Wire frame body; 222. Wire frame section; 2221. Protrusion; 223. Hook; 300. Rotor assembly; 310. Rotor housing; 320. Magnetic housing; 330. Permanent magnet; 400. Mounting tube; 410. Wire hole; 420. Positioning protrusion; 430. Limiting protrusion; 431. Limiting surface; 500. Bearing; 600. Snap ring; 700. Spring. Detailed Implementation

[0025] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art.

[0026] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0027] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0028] Figure 1 A flowchart illustrating a method for fabricating a stator assembly according to an embodiment of the present disclosure is shown; Figure 2 A three-dimensional structural schematic diagram of a brushless DC motor according to an embodiment of the present disclosure is shown; Figure 3 A side view of a brushless DC motor according to an embodiment of the present disclosure is shown; Figure 4 It shows Figure 3 The AA cross-sectional structural diagram shows in detail the assembly relationship of various internal components of the motor (such as stator assembly, rotor assembly, bearings, mounting tubes, etc.); Figure 5 An exploded structural diagram of a brushless DC motor according to an embodiment of the present disclosure is shown, clearly demonstrating the disassembled state of each major component (such as the motor drive board, stator assembly, rotor assembly, mounting tube, etc.). Figure 6A partially exploded structural diagram of the stator assembly in a brushless DC motor according to an embodiment of the present disclosure is shown, with a focus on illustrating the fit between the stator core and the insulated wire frame; Figure 7 An exploded structural diagram of a rotor assembly in a brushless DC motor according to an embodiment of the present disclosure is shown, illustrating the stacking relationship of the rotor housing, the magnetic shell, and the permanent magnet; Figure 8 A schematic diagram of the mounting tube in a brushless DC motor according to an embodiment of the present disclosure is shown, detailing features such as positioning protrusions, limiting protrusions, and wire passage holes.

[0029] This disclosure first provides a method for processing a stator assembly, the process of which is as follows: Figure 1 As shown. This method is used to manufacture the stator assembly 200 of a brushless DC motor, and can effectively improve the bonding strength and positioning accuracy between the insulating wire frame 220 and the stator core 210.

[0030] In step S1, a stator core 210 is provided, which includes a stator ring 211 and a plurality of stator teeth 212 distributed circumferentially along the outer wall of the stator ring 211.

[0031] Specifically, the stator core 210 is typically made of multiple silicon steel sheets with the same profile (e.g., cold-rolled non-oriented silicon steel sheets of grade B35A300 or 50W800) fixed together by methods such as stacking, riveting, or welding. The thickness of the silicon steel sheets is generally 0.2mm to 0.5mm, and the stacking factor is usually not less than 0.95. The inner wall of the stator ring 211 is smooth, and its inner diameter is controlled within IT7 grade to ensure the subsequent fitting accuracy with the bearing 500 or mounting tube 400. The tooth tip surface 2121 of the stator teeth 212 is an arc surface or a plane. Its surface quality directly affects the uniformity of the air gap magnetic field of the motor. Therefore, after stamping or stacking, the tooth tip surface 2121 is usually slightly ground or chamfered to remove burrs.

[0032] In a preferred embodiment of this disclosure, the provided stator core 210 requires strict pretreatment before entering the injection molding process. This pretreatment includes: Degreasing treatment: Place the stator core 210 in an ultrasonic cleaning device and use an environmentally friendly water-based cleaning agent to remove oil, cutting fluid, and metal dust that may have adhered to its surface during stamping and handling. The cleaning temperature should be controlled between 50℃ and 70℃, and the cleaning time should be 5 to 10 minutes. Incomplete degreasing can lead to poor bonding between the insulation material and the surface of the stator core 210 during injection molding, resulting in porosity or delamination.

[0033] Drying treatment: Place the degreased stator core 210 into a constant temperature drying oven for drying. The drying temperature is set to 120℃ to 150℃ and the drying time is 30min to 60min to completely remove moisture and residual solvent.

[0034] Preheating: Before injection molding, the stator core 210 is preheated to 80°C to 150°C. The selection of the preheating temperature needs to take into account both the melting temperature of the insulation material and the heat capacity of the core. For example, when the insulation material is PPS, the preferred preheating temperature is 130°C to 150°C; when the insulation material is PBT, the preferred preheating temperature is 80°C to 110°C. Preheating can mitigate the rapid cooling effect when the high-temperature molten plastic comes into contact with the low-temperature core after being injected into the mold, preventing the plastic from solidifying too early and affecting the filling effect. It also helps to reduce the thermal stress caused by excessive temperature difference and prevents the molded insulation frame 220 from cracking.

[0035] In this disclosure, the lower limit of the preheating temperature, 80°C, is based on the following considerations: When the preheating temperature is below 80°C, the temperature difference between the surface temperature of the stator core 210 and the molten insulating material (approximately 260°C to 320°C) is too large. This causes the molten plastic to cool rapidly upon contact with the surface of the stator core 210, resulting in a sharp decrease in fluidity. Consequently, it becomes difficult to completely fill the small cavities at the root of the stator teeth 212, easily leading to material shortages or porosity defects. Simultaneously, the excessive temperature difference generates significant thermal stress during the cooling stage, increasing the risk of cracking of the insulating wire frame 220.

[0036] The upper limit of 150℃ for the preheating temperature is based on the following considerations: When the preheating temperature is higher than 150℃, the thermal expansion of the stator core 210 increases, which may lead to an insufficient clearance between it and the positioning mandrel, causing difficulties in mold assembly or jamming; at the same time, excessively high preheating temperatures may cause trace amounts of moisture or grease remaining on the surface of the stator core 210 to form gas at high temperatures, resulting in bubbles during injection molding. Preferably, when PPS insulation material is used, the preheating temperature is further preferably 130℃~150℃; when PBT insulation material is used, the preheating temperature is further preferably 80℃~110℃.

[0037] In step S2, the stator core 210 is installed as an insert in the injection mold, and the stator core 210 is independently positioned radially and axially.

[0038] Specifically, the injection mold includes a positioning mandrel and a clamping block. The positioning mandrel passes through the inner hole of the stator ring 211 to achieve radial positioning of the stator core 210; the clamping block abuts against the axial end face of the stator core 210 to achieve axial positioning of the stator core 210. Radial and axial positioning are independent and do not interfere with each other, thus ensuring that the position of the stator core 210 is precisely fixed during injection molding and will not shift due to injection pressure or melt flow.

[0039] In this embodiment, the injection mold includes a fixed mold and a moving mold that cooperate with each other. A positioning mandrel is disposed on the fixed mold side and extends along the mold opening and closing direction; a clamping block is disposed on the moving mold side and can move axially along the positioning mandrel. When the mold is closed, the positioning mandrel is inserted into the inner hole of the stator ring 211 to achieve radial positioning of the stator core 210; the clamping block abuts against the axial end face of the stator core 210 to achieve axial positioning. The fixed mold and the moving mold form a cavity around the stator core 210 for molding the insulating wire frame 220. However, a cavity for accommodating insulating material is not formed at the position corresponding to the tooth tip surface 2121 of the stator tooth 212, so that the molten insulating material cannot flow through the tooth tip surface 2121, thereby keeping the tooth tip surface 2121 exposed after one injection molding.

[0040] Radial positioning: The positioning mandrel is fixed to one side of the mold, with its central axis parallel to the opening and closing direction of the mold. When the stator core 210 is placed in the mold, the positioning mandrel passes through the inner hole of the stator ring 211. The outer diameter of the positioning mandrel is designed to form a precise clearance fit with the inner hole of the stator ring 211 (e.g., a hole-basis fit of H7 / g6 or H7 / f7). This shaft-hole fit restricts the degree of freedom of movement of the stator core 210 in a plane perpendicular to the axial direction (i.e., the radial plane), achieving precise radial positioning. Since the positioning mandrel passes through the entire inner hole of the stator ring 211, it also ensures that the centerline of the stator core 210 coincides with the centerline of the mold, guaranteeing the coaxiality of the inner and outer circles of the stator after molding.

[0041] Axial positioning: The clamping block is located on one side of the moving mold, with its front end face being a flat annular surface used to abut against the axial end face of the stator core 210. During mold closing, the moving mold drives the clamping block to move towards the fixed mold, and the front end face of the clamping block contacts the end face of the stator core 210 and applies a certain clamping force, thereby restricting the axial movement freedom of the stator core 210. The magnitude of this clamping force needs to be moderate, both to overcome the axial impact force generated by the molten plastic on the core during injection molding and to avoid excessive pressure that could cause core deformation. In this embodiment, the mold closing position is controlled by a limit pin or a limit switch to ensure that the clamping force of the clamping block is within a reasonable range.

[0042] Crucially, the radial positioning function is solely undertaken by the positioning mandrel, and the axial positioning function is solely undertaken by the clamping block. The two are completely decoupled mechanically and operate independently. This independent positioning design, compared to over-positioning or combined positioning methods that simultaneously use a single part to restrict both radial and axial positioning, avoids the stator core 210 being forcibly twisted or jammed due to part machining or assembly errors. Simultaneously, the independent positioning reference ensures the unique and definitive position of the stator core 210 within the mold, thereby guaranteeing high positional accuracy of the injection-molded insulating wire frame 220 relative to the stator core 210.

[0043] Preferably, the stator core 210 placed in the injection mold is a stator core 210 that has undergone degreasing, drying, and preheating treatment, and is positioned in the mold within 40s to 120s after preheating, so that the stator core 210 is injection molded in a preheated state. Preheating treatment helps to improve the bonding force between the stator core 210 and the insulating material and reduces thermal stress caused by temperature difference during injection molding.

[0044] In this step, it is specifically required that the preheated stator core 210 be installed and positioned within a time window of 40 to 120 seconds. This is because if the preheated stator core 210 is exposed to air for too long, its surface temperature will drop below the dew point, causing it to absorb moisture from the air, or the temperature will drop too much to achieve the desired preheating effect. Completing the installation within 40 to 120 seconds ensures that the core enters the injection cavity in a relatively preheated state, while also allowing a reasonable time margin for automated robotic arms or manual operation.

[0045] Compared with structures that use the same positioning element to achieve both radial and axial positioning, this embodiment uses a positioning mandrel and a clamping block to perform positioning functions in different directions, so that positioning errors in each direction will not be transmitted to each other. This reduces the cumulative error caused by the machining tolerance of the stator core 210 and improves the forming position accuracy of the insulation frame 220 relative to the stator core 210.

[0046] In step S3, insulating material is injected into the injection mold to form an insulating wire frame 220 in a single injection molding process. The insulating wire frame 220 includes a wire frame body 221 and a plurality of wire frame portions 222 distributed circumferentially along the wire frame body 221. The stator ring 211 is located inside the wire frame body 221. The wire frame portions 222 cover the outer peripheral wall of the stator teeth 212, while the tooth tip surface 2121 of the stator teeth 212 is exposed outside the wire frame portions 222, that is, the tooth tip surface 2121 is not covered by the insulating material.

[0047] During injection molding, the molten insulating material first fills the cavity corresponding to the wire frame body 221, and then flows along the spaces between each stator tooth 212 to the cavity corresponding to each wire frame section 222, so that the wire frame body 221 and multiple wire frame sections 222 are formed in one step, covering the sidewalls and root of the stator teeth 212, while the tooth tip surface 2121 remains exposed. Since the stator core 210 has already completed radial and axial positioning, the position of each wire frame section 222 relative to the corresponding stator tooth 212 remains consistent.

[0048] It is particularly important to emphasize that the tooth tip surface 2121 of the stator tooth 212 remains exposed outside the wire frame portion 222 during this step. That is, after injection molding, the tooth tip surface 2121 is not covered with any insulating material. To achieve this effect, inserts or sliders are provided in the mold design corresponding to the position of the tooth tip surface 2121. These components form a tight sealant fit with the tooth tip surface 2121 of the stator tooth 212, preventing molten plastic from flowing into this area. In this way, the tooth tip surface 2121 remains a metallic surface, and its positional accuracy relative to the central axis of the stator core 210 remains unchanged before and after injection molding.

[0049] Regarding the selection of injection molding materials and process parameters, the following preferred implementation scheme is adopted in this disclosure: The insulating material is selected from high-performance thermoplastic engineering plastics, which not only need to possess excellent electrical insulation properties (dielectric strength ≥20kV / mm), but also must have good heat resistance (heat distortion temperature ≥200℃), mechanical strength, and dimensional stability. In this embodiment, polyphenylene sulfide (PPS) or polybutylene terephthalate (PBT) is preferred. PPS has higher heat resistance and rigidity, making it suitable for high-temperature working environments; PBT has better flowability and toughness, and its cost is relatively low.

[0050] Injection temperature is set according to material type. For PPS, the injection temperature is usually 290℃ to 320℃; for PBT, the injection temperature is usually 260℃ to 290℃. Precisely controlling the temperature within ±5℃ ensures that the melt has a suitable viscosity, which can fill the complex cavity under high pressure without causing material degradation due to excessive temperature.

[0051] The injection pressure is set to 80MPa to 150MPa. Higher pressure helps overcome the flow resistance of the melt when it flows through the narrow toothed cavity, ensuring that the outline of the wire frame 222 is clear, the filling is full, and there are no shrinkage marks or missing material.

[0052] The holding time is set to 3 to 8 seconds. This holding phase compensates for volume loss caused by material cooling and contraction, preventing pits or internal air bubbles from forming in the product. Too short a holding time will result in insufficient product density, while too long a time will increase internal stress.

[0053] Through the above-mentioned optimized injection molding process, the molten plastic comes into full contact with the surface of the preheated stator core 210 and forms a coating bond. After cooling, a strong coating bond structure is formed, which greatly improves the bonding strength between the insulation frame 220 and the stator core 210.

[0054] In this disclosure, the injection temperature setting needs to be determined based on the melting characteristics and thermal decomposition temperature of the insulating material. When the temperature is below 260°C, the melt viscosity is too high, significantly increasing flow resistance and making it difficult to ensure complete filling of the cavity of the wire frame 222, especially the root of the stator teeth 212, easily leading to short shots or weld lines. When the temperature is above 320°C, the insulating material may undergo thermal degradation, resulting in molecular chain breakage and reducing the mechanical strength and insulation performance of the insulating wire frame 220. Controlling the injection temperature within ±5°C is to ensure the stability of the melt viscosity, making the filling behavior consistent for each injection, thereby ensuring the dimensional repeatability of the insulating wire frame 220.

[0055] In this disclosure, when the injection pressure is below 80 MPa, the melt experiences excessive pressure loss when flowing through the slender and small-section toothed cavity, which can easily cause insufficient filling of the wire frame 222 or surface shrinkage marks. When the injection pressure is above 150 MPa, although it can ensure that the cavity is completely filled, the excessive filling pressure will generate excessive impact force on the positioning mandrel and the stator core 210, which may cause slight deformation of the stator teeth 212 or misalignment of the positioning mandrel, affecting the molding accuracy.

[0056] During the injection molding process, the molten insulating material covers the outer surface of the stator teeth 212 and the stator ring 211, and after cooling, it forms a covering and bonding structure with the stator core 210, thereby improving the bonding strength between the insulating wire frame 220 and the stator core 210, which helps to reduce the risk of the insulating wire frame 220 loosening or shifting during the subsequent winding process.

[0057] In step S4, after cooling and demolding, an integrated assembly structure comprising the stator core 210 and the insulating wire frame 220 is obtained. During demolding, the axial positioning of the stator core 210 is first released, allowing the integrated assembly structure formed by the stator core 210 and the insulating wire frame 220 to move synchronously, avoiding relative displacement or tearing between the insulating wire frame 220 and the stator core 210 during demolding due to axial limitation. Then, the radial positioning of the stator core 210 is released, and the positioning mandrel is withdrawn along the axial direction of the stator core 210, completing the demolding. This demolding sequence effectively protects the integrity of the integrated assembly structure and prevents deformation or damage to the injection molded part.

[0058] The demolding process is another crucial step affecting product quality. This disclosure provides an optimized sequential demolding method: First, the moving mold moves backward, causing the clamping block to retract. At this time, the clamping block releases its contact and pressure on the axial end face of the stator core 210, thus releasing the axial positioning. During this process, since the stator core 210 and the insulating wire frame 220 have become integrated, and the radial positioning mandrel still passes through the inner hole of the stator ring 211, the entire integrated assembly structure is in a free state in the axial direction and can float slightly with the movement of the moving mold. This releases the axial internal stress accumulated in the injection molded part during the cooling process and avoids warping caused by stress concentration.

[0059] Next, the ejection mechanism of the mold (such as ejector pins or push plates) begins to operate, pushing the integrated assembly structure to move axially towards the fixed mold. After moving a certain distance, the locating mandrel completely retracts from the inner hole of the stator ring 211, thus releasing the radial positioning.

[0060] Finally, the integrated assembly structure is removed from the mold or picked up by a robotic arm. This sequence of first removing the clamping block and then pushing the product away from the mandrel ensures that the product is subjected to uniform force during demolding, effectively preventing relative sliding or tearing between the insulating wire frame 220 and the stator core 210 at high temperatures, ensuring the integrity of the interface, and resulting in an integrated assembly structure composed of the stator core 210 and the insulating wire frame 220 tightly injection-molded onto it.

[0061] In step S5, after obtaining the integrated assembly structure, coil windings are formed by winding wires on each wire frame portion 222. During the winding process, the coil windings are wound around the outer surface of the wire frame portion 222 and do not cross the tooth tip surface 2121.

[0062] Specifically, during winding, the tooth top surface 2121 is used as the axial reference to control the axial position of the winding layer, ensuring that the coil windings are neatly arranged on the insulating surface of the wire frame 222 and do not cross the tooth top surface 2121 to contact the metal part of the stator tooth 212.

[0063] Preferably, the coil windings are formed sequentially by alternating windings on adjacent wire frame sections 222. That is, the first wire frame section 222 is wound first, and then the winding is moved to the adjacent wire frame section 222, and so on, which helps to balance the resistance and inductance of each phase winding. Furthermore, after each layer of winding is completed, the coil winding is pressed and shaped using the tooth tip surface 2121 as the axial reference surface to ensure that the coil of that layer is tightly attached before proceeding to the next layer of winding, until all turns are completed.

[0064] The coil is pressed and shaped using a special pressing tool, which pushes the coil flat along the tooth top surface 2121 to ensure that there are no gaps or overlaps between the coil layers, thereby improving the slot fill factor and winding consistency. After winding is completed, a stator assembly 200 with a stator core 210, an insulating wire frame 220, and coil windings is obtained.

[0065] In this embodiment, a flying fork winding device or a needle winding device can be used to wind each wire frame 222. Each wire frame 222 corresponds to a stator tooth 212. The conductor is continuously wound around the outer periphery of the wire frame 222 to form a coil winding. During the winding process, the conductor is always located within the winding area formed by the wire frame 222, and the tooth top surface 2121 is used as the axial limiting reference to prevent the conductor from crossing the tooth top surface 2121.

[0066] During the winding process, the enameled wire (preferably polyurethane or polyesterimide enameled copper wire) is precisely wound into the winding groove formed by the outer surface of the wire frame portion 222. Brackets (i.e., flange portions of the wire frame portion) are provided on both radial sides of the wire frame portion 222 to limit the axial movement range of the coil.

[0067] The key technical feature of this disclosure is that, throughout the winding process, the coil winding is strictly confined to a range that does not cross the tooth tip surface 2121. To achieve this, this method makes full use of the exposed tooth tip surface 2121 as the axial reference plane for winding.

[0068] Specifically, the movement trajectory of the lead feeder (or fly fork arm) of the winding device is referenced to the position of the tooth tip surface 2121. During the winding process, the control system ensures, through sensor detection or program control, that the axial movement endpoint of the lead feeder never exceeds the plane containing the tooth tip surface 2121. Therefore, a small safety distance (e.g., 0.2mm to 0.5mm) is maintained between the end of the coil and the tooth tip surface 2121, but it will not extend beyond the tooth tip surface 2121 onto the adjacent stator tooth 212.

[0069] In this way, the risk of short circuits caused by direct contact between the conductor and the iron core due to the winding crossing the tooth tip 2121 in the traditional process is avoided. At the same time, it ensures that the axial height of each coil is consistent, thereby ensuring the symmetry between each phase winding.

[0070] Furthermore, this embodiment employs an alternating winding method for adjacent wire frame sections 222. For example, for a 12-slot stator, the first slot is wound first, then the second slot, and so on, or an intermittent winding and subsequent rewinding method is used, but in both cases, adjacent slots are wound continuously. This winding sequence helps to reduce the length of jumper wires, lower copper losses, and improve the back EMF waveform of the motor.

[0071] During the winding process, after each layer of winding is completed (e.g., 10 turns per layer), the winding equipment pauses, and a wire pressing and shaping mechanism (such as a pneumatic pressure claw) pushes the coil layer axially inward, using the tooth tip surface 2121 as a reference, to compact and neatly arrange it. After pressing, the winding of the next layer begins. This "wind one layer, press one layer" step is repeated until the designed total number of turns is reached. Wire pressing and shaping not only improves the slot fill factor (by 5% to 10%), but more importantly, it ensures the regularity of the coil end shape, which has a positive impact on the dynamic balance and heat dissipation performance of the motor.

[0072] After winding, subsequent processing such as paint removal, soldering, and lead connection is required to obtain the complete stator assembly 200. Preferably, the winding tension is controlled between 1.5N and 4.5N, and the winding speed is controlled between 1500rpm and 3000rpm to ensure that the coils are tightly arranged without damaging the insulation layer.

[0073] In this disclosure, when the winding tension is less than 1.5N, the enameled wire is not sufficiently tensioned when wound on the surface of the coil frame 222, and the coils and coil layers cannot fit tightly together, resulting in a reduced slot fill factor. Furthermore, the coils may experience fretting wear under electromagnetic force during subsequent use, affecting the insulation life. When the winding tension is greater than 4.5N, the enameled wire is overstretched, which may cause the copper wire diameter to become thinner and the resistance to increase. In severe cases, it may damage the insulation layer of the enameled wire. At the same time, excessive tension will generate a large radial tensile force on the coil frame 222, which may cause the coil frame 222 to undergo elastic deformation or even detach from the stator teeth 212.

[0074] When the winding speed is below 1500 rpm, production efficiency is low, and the wire tension fluctuates greatly during low-speed winding, making it difficult to control. When the winding speed is above 3000 rpm, the enameled wire is prone to jumping under high-speed motion, leading to disordered arrangement, and the dynamic impact force on the wire frame 222 increases, which may damage the injection molded part. Preferably, the winding tension is negatively correlated with the winding speed, that is, a lower tension value is used for high-speed winding, and a higher tension value can be used for low-speed winding.

[0075] This disclosure also provides a brushless DC motor, the structure of which is as follows: Figures 2 to 8 As shown. The brushless DC motor includes a motor drive board 100, a stator assembly 200, and a rotor assembly 300 sleeved outside the stator assembly 200. The stator assembly 200 includes a stator core 210, an insulating wire frame 220 injection-molded on the stator core 210, and coil windings (not shown) wound on the wire frame portion 222, and the stator assembly 200 is manufactured using the aforementioned processing method.

[0076] Please refer to Figure 4 and Figure 5The stator core 210 is provided with a mounting tube 400 for mounting the brushless DC motor. The mounting tube 400 extends axially along the stator core 210, and one end can be fixed to the motor housing or the load end. Two bearings 500 are installed in the rotor assembly 300 at intervals. The two bearings 500 are respectively sleeved with the mounting tube 400, thereby rotatably supporting the rotor assembly 300 outside the stator assembly 200.

[0077] The rotor assembly 300 includes a rotor housing 310, which is cylindrical. Inside the rotor housing 310 is a magnetically conductive shell 320 made of a magnetically conductive material, and a permanent magnet 330 is fixedly mounted on its inner wall. An air gap is provided between the tooth tip surface 2121 of the stator teeth 212 and the permanent magnet 330 to allow the rotor assembly 300 to rotate freely under electromagnetic force. The mounting tube 400 is made of metal (such as stainless steel or aluminum) and is hollow. It not only supports the weight of the entire motor but also serves to fix it to an external load (such as a fan duct). Preferably, the width of the air gap ranges from 0.3 mm to 0.8 mm.

[0078] In this disclosure, when the air gap width between the stator tooth tip surface 2121 and the permanent magnet 330 is less than 0.3mm, although it can improve the air gap magnetic flux density and increase the torque density of the motor, it places excessively high requirements on the coaxiality accuracy between the stator core 210 and the rotor assembly 300. Even slight assembly deviations can cause the stator tooth 212 and the permanent magnet 330 to make rubbing contact, while the cogging torque pulsation of the motor increases, and the operating noise and vibration intensify. When the air gap width is greater than 0.8mm, the air gap magnetic reluctance increases significantly, the excitation current of the motor increases, and the power factor and efficiency decrease significantly. Preferably, for brushless DC motors with a rated power in the range of 50W to 200W, the air gap width is further preferably 0.4mm to 0.6mm.

[0079] Please continue to refer to Figure 4 One of the bearings 500 (the bearing closer to the motor drive plate 100) abuts against the end of the insulating wire frame 220 to achieve axial limiting. A retaining ring 600 is sleeved on the mounting tube 400, and a spring plate 700 is provided inside the rotor assembly 300. The other bearing 500 (the bearing away from the motor drive plate 100) abuts between the retaining ring 600 and the spring plate 700. The retaining ring 600 is fixed in the retaining ring groove on the outer wall of the mounting tube 400 to limit the outer ring of the bearing 500. The spring plate 700 is located between the inner wall of the rotor housing 310 and the bearing 500 to provide preload force, eliminate the axial clearance of the bearing 500, and ensure the smooth operation of the rotor assembly 300.

[0080] Please refer to Figure 6 and Figure 8The mounting tube 400 has a wire-passing hole 410 corresponding to the motor drive board 100. The lead wire of the coil winding can pass through the wire-passing hole 410 and be electrically connected to the solder pad on the motor drive board 100. The stator ring 211 of the stator core 210 has a positioning groove 2111. The outer wall of the mounting tube 400 has a positioning protrusion 420 that is inserted into the positioning groove 2111 for positioning. The length of the positioning protrusion 420 is less than the groove length of the positioning groove 2111, so that there is a certain adjustment margin in the axial direction between the mounting tube 400 and the stator core 210. At the same time, the anti-rotation positioning is achieved in the circumferential direction through the cooperation between the positioning protrusion 420 and the positioning groove 2111.

[0081] The outer wall of the mounting tube 400 is also provided with a limiting protrusion 430 arranged in the same direction as the positioning protrusion 420. The limiting protrusion 430 has a limiting surface 431 that abuts against the end face of the stator ring 211. The width of the limiting protrusion 430 is greater than the width of the positioning protrusion 420. The limiting protrusion 430 is used to limit the axial insertion depth of the mounting tube 400 in the stator core 210, ensuring the accurate positioning of the mounting tube 400. Multiple limiting protrusions 430 and positioning protrusions 420 are provided, all evenly distributed along the circumference of the mounting tube 400.

[0082] Please refer to Figure 4 and Figure 6 The wire frame 222 has a protrusion 2221, and the end of the insulating wire frame 220 near the motor drive plate 100 has a hook 223 that engages with the motor drive plate 100. One side of the motor drive plate 100 abuts against the protrusion 2221, and the other side of the motor drive plate 100 engages with the hook 223. Thus, the motor drive plate 100 is clamped and fixed between the protrusion 2221 and the hook 223, requiring no additional screws or adhesives, making assembly simple and reliable. After the motor drive plate 100 is installed, the protrusion 2221 provides axial support for the motor drive plate 100, and the hook 223 prevents the motor drive plate 100 from disengaging in the opposite direction, thereby stably fixing the motor drive plate 100 to the insulating wire frame 220.

[0083] A third aspect of this disclosure also provides a fan, which can be an axial fan, a centrifugal fan, or a crossflow fan. The fan includes a fan body (e.g., a fan casing or volute) and a brushless DC motor as described in the second embodiment above. The brushless DC motor is fixed to a central support of the fan body via its mounting tube 400. Multiple fan blades are fixedly mounted on the rotor housing 310 of the rotor assembly 300 by screws or thermal riveting. When the motor is powered on, the rotor assembly 300 drives the fan blades to rotate, generating airflow. Because the stator assembly 200 uses a one-piece injection-molded insulated wire frame 220, and the tooth tip surface 2121 is exposed as a winding reference, the motor has high efficiency, low vibration, and low noise, making it suitable for use in household or industrial fans.

[0084] When the brushless DC motor is powered on, the rotating magnetic field generated by the stator assembly 200 interacts with the permanent magnet 330 of the rotor assembly 300, producing electromagnetic torque. This torque drives the rotor assembly 300 and the fan blades mounted on it to rotate at high speed around the axis of the mounting tube 400, thereby driving airflow and achieving the air delivery function. Due to the adoption of the aforementioned high-precision and high-reliability stator assembly 200, this fan has the advantages of large air volume, low noise, low vibration, and long lifespan, making it particularly suitable for high-end household floor fans, ceiling fans, air purifiers, and server cooling fans.

[0085] In summary, the stator assembly processing method, brushless DC motor, and fan provided in this disclosure, through the designed insert injection molding and independent positioning assembly process, solve the assembly defects of the traditional split frame, realize the efficient and high-precision manufacturing of the stator assembly, and have a significant promoting effect on improving the overall performance of the motor.

[0086] For example, the stator core 210 is formed by stacking silicon steel sheets and has a total of twelve stator teeth 212. After degreasing and drying, the stator core 210 is preheated to 80℃~150℃ and the mold positioning is completed within 40s~120s after the preheating is completed.

[0087] Subsequently, polyphenylene sulfide insulating material is injected into the mold to form an insulated wire frame 220 in a single injection molding process. The wire frame body 221 covers the stator ring 211, and multiple wire frame portions 222 cover the sidewalls of corresponding stator teeth 212, with the tooth top surfaces 2121 remaining exposed. After cooling and demolding, enameled wire is wound around the outer periphery of each wire frame portion 222 to form coil windings, and the motor assembly is completed.

[0088] Testing revealed that the insulated wire frame 220 is firmly bonded to the stator core 210, and the coil windings are neatly arranged, meeting the long-term operation requirements of the brushless DC motor.

[0089] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0090] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A method for processing a stator assembly, characterized in that, include: Step S1, providing a stator core, the stator core including a stator ring and a plurality of stator teeth spaced circumferentially along the outer wall of the stator ring; Step S2: Install the stator core as an insert into the injection mold, and perform independent radial and axial positioning of the stator core. Step S3: Insulating material is injected into the injection mold to form an insulating wire frame in one injection molding process; wherein, the insulating wire frame includes a wire frame body and a plurality of wire frame portions distributed circumferentially along the wire frame body, the stator ring is located in the wire frame body, the wire frame portions cover the outer peripheral wall of the stator teeth, and the tooth top surface of the stator teeth is exposed to the wire frame portions; Step S4: After cooling and demolding, an integrated composite structure including the stator core and the insulating wire frame is obtained; Step S5: After obtaining the integrated assembly structure, a coil winding is formed by winding wire around each of the wire frame parts. During the winding process, the coil winding is wound around the outer surface of the wire frame part and does not cross the tooth top surface, thus obtaining a stator assembly having the stator core, the insulating wire frame and the coil winding.

2. The method for processing a stator assembly according to claim 1, characterized in that, The injection mold includes a positioning mandrel and a clamping block. In step S2, the positioning mandrel is used to radially position the inner hole of the stator ring, and the clamping block is used to axially position the stator core by abutting against the axial end face of the stator core, so that the stator core remains in a fixed position during the injection molding process.

3. The method for processing the stator assembly according to claim 1, characterized in that, In step S2, the stator core placed in the injection mold is the stator core that has undergone degreasing, drying and preheating treatment, and the mold positioning is completed within 40s to 120s after preheating, so that the stator core is injection molded in a preheated state.

4. The method for processing a stator assembly according to claim 1, characterized in that, In step S3, the insulating material is a thermoplastic engineering plastic, the injection temperature is 260℃~320℃, the injection pressure is 80MPa~150MPa, and the holding time is 3s~8s.

5. The method for processing the stator assembly according to claim 2, characterized in that, In step S4, during demolding, the axial positioning of the stator core is first released, so that the integrated structure formed by the stator core and the insulating wire frame moves synchronously. Then, the radial positioning of the stator core is released, and the positioning mandrel is removed along the axial direction of the stator core to complete the demolding.

6. The method for processing a stator assembly according to claim 1, characterized in that, In step S5, the coil windings are formed sequentially by alternating windings of adjacent wire frame sections. After each layer of winding is completed, the coil windings are pressed and shaped using the tooth top surface as the axial reference surface before the next layer of winding is performed.

7. A brushless DC motor, characterized in that, The device includes a motor drive board, a stator assembly, and a rotor assembly sleeved outside the stator assembly. The stator assembly includes a stator core, an insulating wire frame injection molded on the stator core, and a coil winding wound on the wire frame portion of the insulating wire frame. The stator assembly is manufactured using the processing method described in any one of claims 1 to 6. The stator core is fitted with a mounting tube for mounting the brushless DC motor, and the rotor assembly is fitted with two bearings arranged at intervals, which are respectively sleeved with the mounting tube.

8. The brushless DC motor according to claim 7, characterized in that, The rotor assembly includes a rotor housing, a magnetic conductive shell inside the rotor housing, a permanent magnet installed inside the magnetic conductive shell, and a gap is provided between the tooth tip surface of the stator teeth and the permanent magnet.

9. The brushless DC motor according to claim 7, characterized in that, One of the bearings abuts against the end of the insulating wire frame, the mounting tube is fitted with a retaining ring, the rotor assembly is provided with a spring plate, and the other bearing abuts between the retaining ring and the spring plate.

10. The brushless DC motor according to claim 7, characterized in that, The mounting tube has a wire-passing hole corresponding to the motor drive board. The stator ring of the stator core has a positioning groove. The outer wall of the mounting tube has a positioning protrusion that is inserted into the positioning groove for positioning. The length of the positioning protrusion is less than the groove length of the positioning groove.

11. The brushless DC motor according to claim 10, characterized in that, The outer wall of the mounting tube is provided with a limiting protrusion arranged in the same direction as the positioning protrusion. The limiting protrusion is provided with a limiting surface that abuts against the end face of the stator ring. The width of the limiting protrusion is greater than the width of the positioning protrusion.

12. The brushless DC motor according to claim 7, characterized in that, The wire frame is provided with a protrusion, and the end of the insulated wire frame near the motor drive board is provided with a hook that engages with the motor drive board. One side of the motor drive board abuts against the protrusion, and the other side of the motor drive board engages with the hook.

13. A fan, characterized in that, The device includes a fan body and a brushless DC motor as described in any one of claims 7 to 12, wherein the brushless DC motor is connected to the fan body and fan blades are mounted on the rotor assembly.

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