Miniature motor stator low-pressure injection mold and process

Abstract

The application discloses a micro motor stator low-pressure injection mold and process, and relates to the technical field of motor stators.The steps include the following: firstly, the stator is pre-inspected and cleaned, and the processed stator is preheated; then, the injection mold is preheated, a mold release agent is sprayed in the cavity of the injection mold, and the stator is placed in the cavity; the prepared packaging raw material is added to the barrel of the injection mechanism, and the packaging raw material is heated and melted in the barrel; then, the injection mechanism parameters are adjusted, so that the melted packaging raw material is injected from the injection runner to the cavity and fills the stator; after injection is completed, the cavity is pressure maintained, and after the packaging raw material in the cavity and the stator are cooled and solidified, demolding is performed; finally, the demolded stator is deburred. The application solves the problems of low efficiency, hollow glue leakage, black dregs, damage to the lead wire caused by high-pressure injection process, and short circuit of the winding, and realizes efficient, lossless and high-quality packaging of the stator.

Description

Technical Field

[0001] This invention relates to the field of motor stator technology, and more specifically to a low-pressure injection mold and process for a micro motor stator. Background Technology

[0002] Stator encapsulation is a critical process in motor manufacturing. It involves impregnating, covering, filling, injection molding, and potting the stator core, winding copper wires, and winding ends with polymer insulating materials to form an integrated structure. Traditionally, stator encapsulation is achieved through manual mold-pouring or high-pressure injection molding. However, while manual potting can protect the windings from mechanical damage, it suffers from extremely low efficiency, large quality fluctuations, voids, and brittle materials prone to crumbling. High-pressure injection molding, while highly efficient, inevitably damages the leads and windings due to the high-pressure, high-temperature environment, leading to short-circuit and open-circuit risks. Neither of these processes can simultaneously meet the stringent requirements of military and high-end industrial applications for high efficiency, high reliability, high insulation, no pollution, and long lifespan. Therefore, a new process is urgently needed that can achieve perfect filling, rapid molding, and damage-free encapsulation under extremely low pressure. Summary of the Invention

[0003] To address the existing technical problems, this invention provides a low-pressure injection mold and process for micro motor stators, which solves the problems of low efficiency, voids and leakage of glue, black residue in manual glue filling, as well as damage to lead wires and short circuits in windings caused by high-pressure injection molding, thus achieving efficient, non-destructive, and high-quality encapsulation of the stator.

[0004] The technical solution adopted in this invention is as follows: A low-pressure injection mold for a micro motor stator is provided, including an upper base and a lower base disposed on an injection molding machine. The upper base is disposed on an upper mold base, and the lower base is disposed on a lower mold base. The upper mold base and the lower mold base are provided with cavities for placing the stator, and their sides are connected to the cavities and provided with injection channels. The injection channels are connected to the pipes of an external injection mechanism. The upper mold base can be radially moved relative to the position of the lower base so that the upper mold base and the lower mold base can close or open the mold.

[0005] In some embodiments, at least two cavities are provided, and each cavity is provided with a transverse positioning boss that matches the outer circle of the stator.

[0006] On the other hand, a low-pressure injection molding process for a micro motor stator is provided, including the aforementioned injection mold, the steps of which include: First, the stator is pre-inspected and cleaned, and then preheated. Next, the injection mold is preheated, and a release agent is sprayed into the cavity of the injection mold before the stator is placed into the cavity. Next, the prepared encapsulation material is added to the barrel of the injection mechanism, and the encapsulation material is heated and melted in the barrel. Then, the parameters of the injection mechanism are adjusted so that the molten encapsulation material is injected from the injection channel into the cavity and fills the stator. After injection, pressure is maintained in the cavity. After the encapsulating material and stator in the cavity cool and solidify, demolding is performed. Finally, the stator after demolding is deburred.

[0007] In some embodiments, stator pre-inspection and cleaning includes visual inspection, cleaning treatment, and electrical retesting, wherein... Visual inspection: Confirm that the winding is undamaged, the ends are well shaped, and the lead wires are in the correct position; Cleaning process: Use clean compressed air to blow away impurities from the stator slots and ends; Electrical retest: Randomly check the insulation resistance and withstand voltage to confirm that the electrical performance of the winding is qualified.

[0008] In some embodiments, the cleaned stator is placed in a preheating box, heated to 80°C and kept at that temperature for 10 to 15 minutes, and the injection mold is placed on the injection molding machine worktable and preheated to 80°C.

[0009] In some embodiments, the packaging material is POLYMELY190B hot melt nylon granules. Before use, the nylon granules are placed in a drying oven and dried at 70-90°C for 2-4 hours. The dried material should be sealed and stored.

[0010] In some embodiments, the encapsulation material is added to the barrel of the injection mechanism, and the injection mechanism injects the molten encapsulation material into the cavity through the injection nozzle, runner and gate at a low injection pressure of 2 MPa, and holds the pressure in the cavity for 3 to 5 seconds.

[0011] In some embodiments, the encapsulation material is heated to 210°C in the barrel, the temperature of the encapsulation material in the runner is 180-190°C, the temperature is 170°C when it reaches the gate, and the temperature is 160°C when it contacts the stator in the cavity, so as to form a temperature gradient control of the encapsulation material during the injection and stator molding process.

[0012] In some embodiments, the injection mechanism slowly injects the molten encapsulation material into the cavity in a laminar flow manner, sequentially filling the stator outer peripheral area, the stator slot interior, the tiny gaps between the multilayer conductors, the stator end space, and the root of the lead wire.

[0013] In some embodiments, the encapsulated material inside the cavity and the stator are naturally cooled for 20 seconds, and the hot melt nylon is cooled to below 80°C to solidify and set.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: This invention uses an extremely low pressure of 2MPa to drive the molten encapsulation material to fill the stator in a laminar flow manner. Combined with precise temperature gradient control of 210℃-160℃ during the injection and stator molding process of the encapsulation material, it completely eliminates the problems of voids, glue leakage and insulation damage that cannot be overcome in traditional processes, thereby improving the encapsulation quality.

[0015] This invention integrates multiple cumbersome processes into a single injection molding process, reducing the molding cycle from several hours to several minutes, improving molding efficiency, and automating the entire process to reduce scrap rate.

[0016] The packaging material of this invention uses POLYMELY190B hot melt nylon granules, which are thermoplastic materials. Through a physical cooling process, the molten temperature only needs to be reduced to below 80°C to complete the shaping, thus enabling rapid solidification. Attached Figure Description

[0017] The present invention will be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a structural diagram of the low-pressure injection mold for the micro motor stator of this invention; Figure 2 This is a flowchart of the low-pressure injection molding process for the micro motor stator of the present invention.

[0018] The markings in the diagram are: 1-upper base, 2-lower base, 3-upper mold base, 4-lower mold base. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0020] It should be noted that similar labels in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0021] It should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0023] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] like Figure 1 As shown, this embodiment provides a low-pressure injection mold for a micro motor stator. The mold is made of iron and includes an upper base 1 and a lower base 2 on the injection molding machine. The upper base 1 is located on an upper mold base 3, and the lower base 2 is located on a lower mold base 4. The upper mold base 3 and the lower mold base 4 are provided with cavities for placing the stator. The sides of the upper mold base 3 and the lower mold base 4 are connected to the cavities and have injection channels. The injection channels are connected to the external injection mechanism pipes. The upper mold base can be moved radially relative to the lower base 2 so that the upper mold base 3 and the lower mold base 4 can close or open the mold.

[0025] In this application, the mold cavity has at least two cavities, forming a two-outlet structure. Two stators can be packaged simultaneously in a single molding cycle, improving processing efficiency. Each cavity has a transverse positioning boss that matches the outer circle of the stator. The outer circle of the stator is designed with six grooves evenly distributed at 60 degrees. The grooves precisely match the transverse positioning bosses in the cavity, achieving accurate positioning of the stator in the mold, ensuring the coaxiality of the stator and the cavity, making the encapsulation layer thickness uniform after injection molding, ensuring that the inner hole of the stator is concentric with the rotor to be assembled laterally, avoiding uneven air gap and power reduction caused by eccentricity, and preventing the stator from being displaced by the impact of melt flow during injection molding.

[0026] This injection molding device uses compressed air instead of hydraulic actuation, precisely controlling the injection pressure at a low level of 2MPa. This is far below the critical loss threshold for lead wire deformation, enameled wire coating damage, and amorphous core cracking, ensuring that the mechanical stress on the stator assembly during the encapsulation process is almost zero. At the same time, it is sufficient to overcome the capillary resistance in the tiny gaps of the windings, driving the melt to slowly advance in a laminar flow manner, achieving complete filling of all microscopic voids. Low-pressure injection molding has extremely low requirements for mold strength; the pressure of 2MPa is only equivalent to the hydrostatic pressure of 200 meters deep water. Ordinary iron molds or even aluminum alloy molds can meet the requirements, eliminating the need for the expensive high-strength steel molds required for high-pressure injection molding.

[0027] like Figure 2 As shown, a low-voltage injection molding process for a micro motor stator includes an injection mold, and the steps include: firstly, visual inspection, cleaning, and electrical retesting of the stator; wherein, visual inspection confirms that the windings are undamaged, the ends are well shaped, and the lead wires are in the correct position; cleaning uses clean compressed air to blow away impurities in the stator slots and at the ends; and electrical retesting checks the insulation resistance and withstand voltage to confirm that the winding electrical performance is qualified.

[0028] Secondly, the inspected and cleaned stator is placed in a preheating chamber for preheating to 80°C and held for 10-15 minutes. Simultaneously, the injection mold is placed on the injection molding machine worktable and preheated to 80°C. A release agent is sprayed into the cavity of the injection mold, and then the preheated stator is placed into the cavity of the preheating mold. Stator preheating improves the fluidity of the subsequently injected melt, slows down the cooling rate of the stator surface when it comes into contact with the injected melt, and allows the melt to fill the tiny gaps for a longer time. At the same time, it can reduce the temperature difference between the melt and the stator, reduce the thermal stress caused by rapid thermal expansion and contraction, and facilitate the molecular-level bonding of the melt with the stator core and windings. Furthermore, mold preheating maintains the fluidity of the melt, reduces the injection pressure requirement, improves the temperature matching between the mold and the stator, and reduces stress.

[0029] Next, the prepared encapsulation material is added to the barrel of the injection unit. The encapsulation material is POLYMELY190B hot-melt nylon granules, a one-component thermoplastic polyamide with 100% solids content, free of organic solvents, and a melting temperature of 210–230°C. Utilizing its thermoplasticity, high toughness, and one-component intrinsic properties, it solves the problem of brittle spalling and contamination associated with traditional epoxy resins. The linear structure of the thermoplastic nylon molecular chains causes elastic deformation rather than brittle fracture under stress, completely eliminating the generation of black, hard particles. Its 100% solids content eliminates the need for on-site... The on-site mixing of the adhesive eliminates the possibility of impurities being introduced at the source of the process; its excellent fluidity makes it suitable for low-pressure injection molding, allowing it to fully fill the winding gaps under a low pressure of 2MPa, forming a dense protective layer free of bubbles and voids. Through a physical cooling process, it can be quickly solidified by simply lowering the melt temperature to below 80℃. After solidification, it has high toughness and no risk of brittle collapse. It has excellent adhesion to copper wire, amorphous iron core, and insulating materials. Before use, place the nylon granules in a drying oven and dry them at 70-90℃ for 2-4 hours. The dried material should be stored in a sealed container.

[0030] Finally, the encapsulation material is added to the barrel of the injection mechanism and heated to melt. The injection mechanism injects the molten encapsulation material into the cavity through the injection nozzle, runner and gate at a low injection pressure of 2MPa to fill the stator. The pressure is held in the cavity for 3 to 5 seconds. After the encapsulation material and stator in the cavity cool and solidify, the mold is demolded. Finally, the flash of the demolded stator is removed.

[0031] This embodiment integrates the traditional multiple cumbersome processes into a single injection molding process through the above-described injection molding process, shortening the molding cycle from several hours to several minutes, improving molding efficiency. Moreover, the entire process is automated, reducing the scrap rate and solving the problems of low efficiency, voids and leakage, black residue, and damage to lead wires and short circuits in windings caused by high-pressure injection molding. This achieves efficient, non-destructive, and high-quality encapsulation of the stator.

[0032] In this application, the injection mechanism slowly injects the molten encapsulation material into the cavity in a laminar flow manner, sequentially filling the outer periphery of the stator, the inner cavity of the stator slot, the tiny gaps between the multilayer conductors, the space at the end of the stator, and the root of the lead wire. After the injection is completed, the encapsulation material in the cavity and the stator are naturally cooled for 20 seconds, and the hot melt nylon is cooled to below 80°C and solidified.

[0033] The encapsulation material is heated to 210°C in the barrel, and its temperature is 180-190°C in the runner. When it reaches the gate, the temperature is 170°C, and when it contacts the stator in the cavity, the temperature is 160°C. The melt at 160°C still maintains sufficient fluidity and can fully fill the winding gap under a low pressure of 2MPa, achieving a perfect balance between fluidity and protection. This allows the encapsulation material to form a temperature gradient control during the injection and stator molding process.

[0034] By utilizing the physical principle of natural cooling of the melt in the flow channel, the melt temperature on the contact winding surface is reduced to approximately 160°C. This 160°C is far below the critical threshold for softening and damage to the varnish film (180°C for long-term use and above 200°C for short-term use). At the same time, the melt maintains sufficient fluidity, achieving a perfect balance between "high-temperature melting to ensure fluidity and low-temperature contact to protect the insulation layer." Combined with the synchronous temperature control strategy of preheating the stator at 80°C and the mold at 80°C, thermal shock is further reduced and the melt filling time is extended.

[0035] It is worth noting that when the melt flows through the runner and gate, its temperature naturally drops to about 160°C through heat exchange with the mold wall and air. The 180-grade enameled wire used in this application has a long-term temperature resistance rating of 180°C and a short-term temperature resistance of over 200°C. The contact temperature of 160°C is far below the critical threshold for softening and damage to the enamel film. By precisely designing the runner length and mold temperature, the melt naturally cools to about 160°C when it contacts the winding surface, which is far below the threshold for enamel film damage. At the same time, the winding is heated for only a few seconds, and the heat is quickly carried away by the mold before it can be conducted to the deeper layers of the winding. This forms a thermal process of "instantaneous thermal shock and rapid thermal equilibrium," ensuring that the insulation layer of the enameled wire remains intact.

[0036] This embodiment completely avoids the risk of mechanical damage to the stator's delicate structure caused by high-pressure injection molding by driving the encapsulation material melt to fill the stator in a laminar flow manner under extremely low pressure of 2MPa. This ensures the integrity and reliability of the leads and windings. Furthermore, under the low pressure of 2MPa, the melt is pushed forward at a low speed and smoothly, producing only a gentle surrounding effect on the winding ends without any impact damage. Combined with the precise temperature gradient control of 210℃-160℃ during the injection and stator molding process of the encapsulation material, the melt contact temperature is much lower than the softening point of the varnish film. The varnish film remains in a hard solid state throughout the encapsulation process and will not deform or break even under slight pressure. Through this dual protection mechanism of "extremely low pressure + low temperature contact," true zero-damage encapsulation of the leads and windings is achieved. Fatal faults such as inter-turn short circuits and lead breakage are completely eliminated, and problems such as voids, glue leakage, and insulation damage that cannot be overcome in traditional processes are completely eliminated, thus improving the encapsulation quality.

[0037] A performance comparison test was conducted using 18 unsealed stators from the same batch, including 6 low-pressure injection molded, 6 high-pressure injection molded, and 6 manually potted stators, as shown in Table 1. Table 1:

[0038] Through comparative testing, the same motor was tested under the same conditions, with only the stator being replaced by injection molding and the stator being made by potting. The results showed that the output power of the stator made by injection molding was better than that of the stator made by potting. Furthermore, the stator made by injection molding process made up for the shortcomings of traditional potting process, such as slag shedding, voids, and poor insulation performance. Therefore, the injection molding process has better reliability and safety than the traditional potting process.

[0039] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made under the concept of the present invention using the description and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A low-pressure injection mold for a micro motor stator, characterized in that, The system includes an upper base and a lower base mounted on an injection molding machine. The upper base is mounted on an upper mold base, and the lower base is mounted on a lower mold base. The upper and lower mold bases are provided with cavities for placing stators, and their sides are connected to the cavities and have injection channels. The injection channels are connected to external injection mechanism pipes. The upper mold base can be radially moved relative to the lower base position to allow the upper and lower mold bases to close or open the mold.

2. The low-pressure injection mold for a micro motor stator according to claim 1, characterized in that, The mold cavity is provided with at least two cavities, and each cavity is provided with a transverse positioning boss that matches the outer circle of the stator.

3. A low-pressure injection molding process for a micro motor stator, characterized in that, Including the injection mold of claim 1, the steps include: First, the stator is pre-inspected and cleaned, and then preheated. Next, the injection mold is preheated, and a release agent is sprayed into the cavity of the injection mold before the stator is placed into the cavity. Next, the prepared encapsulation material is added to the barrel of the injection mechanism, and the encapsulation material is heated and melted in the barrel. Then, the parameters of the injection mechanism are adjusted to inject the molten encapsulation material from the injection channel into the cavity and fill the stator. After injection, pressure is maintained in the cavity. After the encapsulating material and stator in the cavity cool and solidify, demolding is performed. Finally, the stator after demolding is deburred.

4. The low-pressure injection molding process for the micro motor stator according to claim 3, characterized in that, Stator pre-inspection and cleaning includes visual inspection, cleaning treatment, and electrical retesting, among which, Visual inspection: Confirm that the winding is undamaged, the ends are well shaped, and the lead wires are in the correct position; Cleaning process: Use clean compressed air to blow away impurities from the stator slots and ends; Electrical retest: Randomly check the insulation resistance and withstand voltage to confirm that the electrical performance of the winding is qualified.

5. The low-pressure injection molding process for the micro motor stator according to claim 3, characterized in that, Place the cleaned stator in a preheating box, heat it to 80°C and keep it at that temperature for 10-15 minutes, and place the injection mold on the injection molding machine worktable to preheat it to 80°C.

6. The low-pressure injection molding process for the micro motor stator according to claim 3, characterized in that, The packaging material uses POLYMELY190B hot melt nylon granules. Before use, the nylon granules are placed in a drying oven and dried at 70-90℃ for 2-4 hours. The dried material should be sealed and stored.

7. The low-pressure injection molding process for the micro motor stator according to claim 3, characterized in that, The encapsulation material is added to the barrel of the injection mechanism. The injection mechanism injects the molten encapsulation material into the cavity through the injection nozzle, runner and gate at a low injection pressure of 2MPa, and holds the pressure in the cavity for 3 to 5 seconds.

8. The low-pressure injection molding process for the micro motor stator according to claim 7, characterized in that, The encapsulation material is heated to 210°C in the barrel, and its temperature is 180-190°C in the runner. When it reaches the gate, the temperature is 170°C, and when it contacts the stator in the cavity, the temperature is 160°C, so as to form a temperature gradient control of the encapsulation material during the injection and stator molding process.

9. The low-pressure injection molding process for the micro motor stator according to claim 7, characterized in that, The injection mechanism slowly injects the molten encapsulation material into the cavity in a laminar flow manner, sequentially filling the stator outer periphery, the stator slot interior, the tiny gaps between multiple layers of conductors, the stator end space, and the root of the lead wires.

10. The low-pressure injection molding process for the micro motor stator according to claim 1, characterized in that, The encapsulated material and stator are naturally cooled for 20 seconds inside the cavity, and the hot melt nylon is cooled to below 80°C to solidify and set.

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