Full-coating injection molding method of flat wire stator motor

Abstract

The invention discloses a full-coating injection molding method for a flat wire stator motor, and belongs to the technical field of stator core processing, and the method comprises the following steps: preforming a flat wire coil: bending a linear flat wire into a preset U-shaped coil by using bending equipment, transferring the U-shaped coil to a rotary fixed seat, and carrying out injection molding on the U-shaped coil; and arranging the U-shaped coils according to the final shape of the motor stator slot to finally form the shape of the flat wire stator. Removing surface impurities: washing the surface of the flat wire stator with plasma water or alcohol to remove grease and an oxide layer, and then drying; and spraying an insulation bottom layer: moving the dried rotary fixing seat and the formed flat wire stator to a spraying chamber, spraying matte water-based UV paint onto the flat wire stator through an inner spraying gun and an outer spraying gun until spraying is completed, forming the insulation bottom layer, improving the filling degree in a stator iron core groove, and improving the insulation performance and the stability of the flat wire.

Description

Technical Field

[0001] The invention belongs to the technical field of motor stator core processing, and relates to a flat wire processing technology for motor stator windings, and in particular to a full-cover injection molding method for a flat wire stator motor. Background Art

[0002] The windings between the flat wire and the stator core of new energy vehicle motors are usually insulated with insulating paper. After the insulating paper is set, the stator core is impregnated with insulating varnish. After the insulating varnish is cured, the flat wire is fixed to form a strong overall structure. However, during the use of the motor, due to the gap between the insulating paper and the flat wire, the flat wire will shake in the stator slot during long-term use, affecting the quality of the motor and shortening the motor life.

[0003] In the prior art, the invention patent with publication number (C) N117154986 discloses a multi-composite insulating sheet and a flat wire motor stator, belonging to the field of motor insulation technology. The specific scheme is as follows: it includes a substrate layer and a first thermosetting resin layer and a second thermosetting resin layer respectively coated on both sides of the substrate layer, the substrate layer contains a first heat-expanding material, the first thermosetting resin layer and / or the second thermosetting resin layer contain a second heat-expanding material, and the first heat-expanding material and the second heat-expanding material expand upon heating.

[0004] This multi-composite insulating sheet material can fully fill the gaps between the flat wires within the slots, as well as between the insulating sheet and the core slots, helping to improve insulation performance. It also exhibits high P(D)IV, long corona life, high temperature resistance, and high mechanical properties, meeting the long-term use requirements of new energy vehicles in high-voltage, high-speed, and vibration environments. While the aforementioned structure reduces the gaps within the core slots to a certain extent, the patent primarily addresses structural improvements to the insulation layer of the flat wires themselves. Due to the properties of thermosetting materials, expansion during heating is difficult to control, easily leaving gaps between the core and the flat wires, impacting product quality. Summary of the Invention

[0005] The purpose of the present invention is to overcome the technical problems in the prior art such as the difficulty in controlling the expansion state of thermosetting materials, which leads to gaps between the stator core slots and the flat wires, and affects product quality after long-term use. A full-encapsulation injection molding method for a flat wire stator motor is provided, which allows the insulating material to fully fill the stator slot gaps, thereby improving the insulation performance of the motor and the stability of the flat wires, and significantly improving the moisture and heat resistance and mechanical strength of the motor.

[0006] In order to solve the above technical problems, the present invention provides a full-cover injection molding method for a flat wire stator motor, the method comprising the following steps: Step 1: Flat Wire Coil Preforming: Use a bending machine to bend the straight flat wire into a predetermined U-shaped coil. The U-shaped coil is transferred to a rotating fixed seat and arranged according to the final shape of the motor stator slots to form the shape of the flat wire stator. Step 2: Remove surface impurities: Rinse the surface of the flat wire stator with plasma water or alcohol to remove grease and oxidation layer, and then dry it; Step 3: Spraying the insulating base layer: Move the dried rotating holder and the formed flat wire stator to the spraying room, and spray the matte water-based UV paint onto the flat wire stator using the inner and outer spray guns. During the spraying process, rotate the entire flat wire stator at a constant speed through the rotating holder for 1-3 turns until the spraying is completed to form the insulating base layer. Step 4: Curing the insulating base: Move the rotating holder and the sprayed flat wire stator to the UV irradiation room and cure them with LED light. Step 5: Build a casting model: remove the solidified flat wire stator from the rotating fixed seat and insert the flat wire stator into the motor core mold seat. The motor core mold seat has a notch corresponding to the flat wire stator. The entire motor core mold seat is installed in two side injection molds that can be sealed and buckled with each other. The two side injection molds are controlled by a driving motor to abut against each other to form a casting cavity. The bottom of the motor core mold seat is sealed with an isolation plate, and a fixed mold plate is used to abut against the bottom of the isolation plate. Step 6, insulation pouring: The heating device installed on the side injection mold preheats the entire motor core mold base, and the heated liquid insulation material is injected into the pouring cavity at 80-300°C through the movable platen. The heating device is started and maintains the pouring temperature; Step 7, cooling and demoulding: Cool naturally to below 80℃, demould after 1-2 hours, trim the edges, and complete the insulation full-cover injection molding.

[0007] As a further improvement measure of the present invention, in the above step 3, the matte water-based UV paint includes 60-70% epoxy acrylate, 20-30% polyurethane acrylate, 5-10% nano-aluminum oxide, 2-5% boron nitride and 1-3% photoinitiator.

[0008] As a further improvement measure of the present invention, in the above step 3, the thickness of the insulating bottom layer is 20-50 μm.

[0009] As a further improvement measure of the present invention, in the above step 4, the wavelength of the LED light source is 365-420 nm.

[0010] As a further improvement measure of the present invention, in the above step 3, the pressure of the inner spray gun and the outer spray gun is 0.2-0.4 MPa, and the inner spray gun and the outer spray gun are set at an angle of 45-60 degrees with each U-shaped coil.

[0011] As a further improvement measure of the present invention, in the above step 2, the drying method is oven drying, the drying temperature is 80-100°C, the drying time is 1-2 hours, the solvent and moisture are removed, and the mixture is naturally cooled to below 60°C before being taken out.

[0012] As a further improvement measure of the present invention, in the above step 6, the preheating temperature is maintained at 80-120 degrees.

[0013] As a further improvement measure of the present invention, in the above step 6, the pouring temperature is maintained at 150-200 degrees for 1-2 hours.

[0014] As a further improvement measure of the present invention, in the above-mentioned step 6, the liquid insulating material is epoxy resin.

[0015] As a further improvement measure of the present invention, in the above step 6, a plurality of exhaust holes are provided on the top of the lateral injection mold.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention uses plasma water or alcohol to clean the surface of the flat wire stator, effectively removes grease and oxide layer, enhances the adhesion of subsequent insulating coating, and forms a uniform insulating bottom layer by spraying matte water-based UV paint and UV curing. Combined with the addition of nano-aluminum oxide and boron nitride, the high temperature resistance and dielectric strength of the insulating layer are improved; 2. The present invention uses a rotating fixed seat in conjunction with internal and external spray guns for uniform spraying to ensure that the insulating layer is covered without dead angles, avoiding the risk of breakdown due to local weakness; 3. The present invention preheats the motor core mold seat before pouring and maintains the temperature during the injection molding process. The internal insulating material always remains in a flowing state to avoid excessive heat dissipation in some areas, or partial cooling causing premature solidification of the structure and residual bubbles. By heating, the whole is fully contacted to remove bubbles, and then uniform cooling is performed to make the insulating material fully fill the stator slot gap, forming a bubble-free and crack-free fully encapsulated structure, greatly improving the moisture and heat resistance and mechanical strength of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] Example 1: Figure 1 As shown, a full-cover injection molding method for a flat wire stator motor includes the following steps: Step 1: Preform the flat wire coils. Using automated bending equipment, the straight flat wire is bent into the desired U-shaped coils. The copper wire has a cross-sectional size of 2mm x 5mm and a bend angle of 180°. The U-shaped coils are then transferred sequentially to a rotating fixture and arranged in the order of the final 36-slot motor stator configuration, forming a complete flat wire stator structure.

[0020] Step 2: Remove surface impurities. First, rinse the assembled flat wire stator surface with plasma ionizer, then rinse with anhydrous ethanol to remove any remaining grease and oxide, enhancing the adhesion of the subsequent insulation coating. After rinsing, dry the flat wire stator in an oven at 90°C for 1.5 hours to remove any solvent and moisture. After drying, allow the stator to cool naturally to 50°C before removing it from the oven.

[0021] Step 3: Spray the insulating base layer. The dried flat wire stator is moved to the spray booth, where a dual-gun spray system, with an inner and outer spray gun, is used to apply a matte water-based UV paint to the stator. The inner spray gun applies pressure at 0.3 MPa, while the outer spray gun applies pressure at 0.35 MPa. The inner and outer spray guns are positioned at a 50° angle to each U-shaped coil. During the spraying process, the entire flat wire stator is rotated at a constant speed of 10 rpm for two revolutions until the coating is complete, forming the insulating base layer with a thickness of 35 ± 5 μm.

[0022] Matte water-based UV paint consists of 65% epoxy acrylate, 25% polyurethane acrylate, 8% nano-aluminum oxide, 3% boron nitride, and 2% photoinitiator. Spraying and UV curing the matte water-based UV paint creates a uniform insulating base layer. The addition of nano-aluminum oxide and boron nitride improves the insulation layer's high-temperature resistance and dielectric strength.

[0023] A rotating fixed seat is used in conjunction with internal and external spray guns for uniform spraying to ensure that the insulation layer is covered without blind spots and avoid the risk of breakdown due to local weaknesses; epoxy acrylate provides high cross-linking density to ensure excellent insulation and adhesion; polyurethane acrylate enhances flexibility to prevent cracking of the coating caused by vibration during motor operation.

[0024] Step 4: Cure the insulation base. Move the rotating mount and the coated flat wire stator to a UV irradiation chamber and irradiate with an LED light source to completely cure the insulation base. The LED light source has a wavelength of 385nm and a light intensity of 100mW / cm². Irradiate for 30 seconds, and the insulation base thickness will be 20-50μm.

[0025] Step 5: Build the casting model. Remove the solidified flat wire stator from the rotating fixture and insert it into the motor core mold base. The motor core mold base has slots corresponding to the flat wire stator. The entire motor core mold base is installed in two side injection molds that can be sealed together. The two side injection molds are controlled by a driving motor to abut and fit together to form a casting cavity. Multiple exhaust holes are set at the top of the side injection mold. A polytetrafluoroethylene isolation plate is used to seal the bottom of the motor core mold base. The fixed mold plate is placed against the bottom of the isolation plate to form a closed casting cavity.

[0026] Step 6: Insulation pouring. The entire motor core mold base is preheated by the heating device installed on the lateral injection mold. The preheating temperature is maintained at 100°C and kept warm for 30 minutes. Liquid insulation material heated to 150°C is injected into the pouring cavity through the injection port of the movable mold plate at a pressure of 1.5MPa. The liquid insulation material is epoxy resin with a viscosity of 500cP. The heating device is started and the temperature of the lateral injection mold is maintained at 180°C±5°C. The pressure is maintained for 1.5 hours to fully fill the epoxy resin, and the air bubbles are discharged through the exhaust hole at the top of the lateral injection mold.

[0027] The motor core mold base is preheated before casting and maintained at this temperature during the injection molding process to ensure that the internal insulation material remains fluid. This prevents excessive heat dissipation in certain areas, or premature solidification of the structure due to partial cooling, which can cause residual bubbles. Heating ensures full contact and removes bubbles throughout the entire mold. Then, uniform cooling ensures that the insulation material fully fills the stator slots, creating a bubble-free, crack-free, fully encapsulated structure, significantly improving the motor's moisture and heat resistance and mechanical strength.

[0028] Step 7: Cool down and demould. Turn off the heating device and allow the lateral injection mold to cool naturally to 75°C. After 1.5 hours, open the mold. Trim the edges, remove the gate and polish the flash to complete the insulation full-coating injection molding, and obtain an insulation-coated stator with a smooth surface. The coating layer is 1.2mm thick and has no bubbles or cracks. The flat wire motor stator manufactured by this embodiment was tested and sliced, and the results showed that the resin filling rate at the notch corners was ≥98%, there were no air holes, and the overall insulation coating effect was good.

[0029] Example 2: This example differs from Example 1 in step 6: the insulation casting process. This example uses a highly thermally conductive modified epoxy resin with 30% alumina filler, resulting in a thermal conductivity of 1.5 W / m·K, compared to the 0.2 W / m·K thermal conductivity of the conventional epoxy resin in Example 1.

[0030] After the high-thermal-conductivity modified epoxy resin is heated to 200°C and injected, the high temperature reduces its viscosity to 200 cP at 200°C, enhancing fluidity and ensuring filling of small gaps. The injection pressure is increased to 2.0 MPa, and the holding time is extended to 2 hours to compensate for the shrinkage of the highly filled resin. The mold temperature is maintained at 200°C ± 5°C, precisely regulated by a PID temperature control system to avoid local overheating and resin degradation. Slice testing of the flat wire motor stator manufactured using this embodiment shows that the resin filling rate at the notch corners is ≥ 99%, there are no air holes, and the overall insulation coating is excellent.

[0031] The above embodiments show that the present invention achieves high-reliability insulation coating by optimizing the cleaning, spraying and pouring processes, and is suitable for high-end application scenarios such as new energy drive motors.

[0032] The above describes the embodiments of the present invention in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. A person skilled in the art may make several modifications and improvements without departing from the present invention, and these should also be considered to fall within the scope of protection of the present invention.

Claims

1. A full-cover injection molding method for a flat wire stator motor, characterized in that: The method comprises the following steps: Step 1: Flat Wire Coil Preforming: Use a bending machine to bend the straight flat wire into a predetermined U-shaped coil. The U-shaped coil is transferred to a rotating fixed seat and arranged according to the final shape of the motor stator slots to form the shape of the flat wire stator. Step 2: Remove surface impurities: Rinse the surface of the flat wire stator with plasma water or alcohol to remove grease and oxidation layer, and then dry it; Step 3: Spraying the insulating base layer: Move the dried rotating holder and the formed flat wire stator to the spraying room, and spray the matte water-based UV paint onto the flat wire stator using the inner and outer spray guns. During the spraying process, rotate the entire flat wire stator at a constant speed through the rotating holder for 1-3 turns until the spraying is completed to form the insulating base layer. Step 4: Curing the insulating base: Move the rotating holder and the sprayed flat wire stator to the UV irradiation room and cure them with LED light. Step 5: Build a casting model: remove the solidified flat wire stator from the rotating fixed seat and insert the flat wire stator into the motor core mold seat. The motor core mold seat has a notch corresponding to the flat wire stator. The entire motor core mold seat is installed in two side injection molds that can be sealed and buckled with each other. The two side injection molds are controlled by a driving motor to abut against each other to form a casting cavity. The bottom of the motor core mold seat is sealed with an isolation plate, and a fixed mold plate is used to abut against the bottom of the isolation plate. Step 6, insulation pouring: The heating device installed on the side injection mold preheats the entire motor core mold base, and the heated liquid insulation material is injected into the pouring cavity at 80-300°C through the movable platen. The heating device is started and maintains the pouring temperature; Step 7, cooling and demoulding: Cool naturally to below 80℃, demould after 1-2 hours, trim the edges, and complete the insulation full-cover injection molding.

2. The method for full-cover injection molding of a flat wire stator motor according to claim 1, characterized in that: In step 3, the matte water-based UV paint includes 60-70% of epoxy acrylate, 20-30% of polyurethane acrylate, 5-10% of nano-aluminum oxide, 2-5% of boron nitride and 1-3% of photoinitiator.

3. The method for full-cover injection molding of a flat wire stator motor according to claim 2, characterized in that: In step 3, the thickness of the insulating bottom layer is 20-50 μm.

4. The method for full-cover injection molding of a flat wire stator motor according to claim 1, characterized in that: In step 4, the wavelength of the LED light source is 365-420 nm.

5. The method for full-cover injection molding of a flat wire stator motor according to claim 3, characterized in that: In step 3, the pressure of the inner spray gun and the outer spray gun is 0.2-0.4 MPa, and the inner spray gun and the outer spray gun are set at an angle of 45-60 degrees with each U-shaped coil.

6. The method for full-cover injection molding of a flat wire stator motor according to claim 1, characterized in that: In step 2, the drying method is oven drying at a drying temperature of 80-100° C. for 1-2 hours to remove the solvent and moisture, and the mixture is naturally cooled to below 60° C. before being taken out.

7. The method for full-cover injection molding of a flat wire stator motor according to claim 1, characterized in that: In step 6, the preheating temperature is maintained at 80-120 degrees.

8. The method for full-cover injection molding of a flat wire stator motor according to claim 7, characterized in that: In step 6, the pouring temperature is maintained at 150-200 degrees for 1-2 hours.

9. The method for full-cover injection molding of a flat wire stator motor according to claim 8, characterized in that: In step 6, the liquid insulating material is epoxy resin.

10. The method for full-cover injection molding of a flat wire stator motor according to claim 9, characterized in that: In step 6, a plurality of vent holes are provided on the top of the side injection mold.

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