An injection molding method for dry unsaturated thermosetting resin for motor rotors

Abstract

This invention relates to the field of casting method technology. The invention provides an injection molding method for dry unsaturated thermosetting resin used in motor rotors, comprising the following steps: (1) preheating the dry unsaturated polyester resin material to 85-95°C using a high-frequency wave or injection molding machine, until it reaches a semi-softened state; (2) cleaning the mold and preheating the iron core and upper and lower molds to 150-180°C; (3) feeding the preheated material into the preheated feed port of the injection molding machine or pressing it into the injection port of the injection molding machine, and injecting it into the mold cavity under a set pressure, covering the magnet; (4) maintaining the pressure of the material in the mold cavity under a set temperature and pressure, allowing it to solidify and form within the mold. This injection molding method enables excellent adhesion between the drive motor rotor and the unsaturated resin material.

Description

Technical Field

[0001] This invention relates to the field of casting method technology, and specifically to an injection molding method for dry unsaturated thermosetting resin for motor rotors. Background Technology

[0002] The motor rotor is the core rotating component of a motor, typically a fixed part formed by curing a rotor core, magnets, and a resin composition for fixing. During motor operation, the rotor is subjected to multiple forces, including high-speed rotation, electromagnetic impact, and temperature changes, placing stringent requirements on its structural stability and reliability. Resin injection molding of the rotor can fix the position of the magnets, preventing them from being completely exposed, and can also improve impact resistance, increase rotor speed, optimize NVH (noise, vibration, and harshness), while improving the motor's waterproof, moisture-proof, and corrosion-resistant properties.

[0003] Existing technologies mostly employ resin injection, where a magnet is inserted into a magnet insertion hole in the rotor core, resin is injected through a resin injection hole located in the magnet insertion hole, and the resin is cured to fix the permanent magnet. However, the bonding force between traditional potting resin and the magnet surface is limited, and there is a risk of the magnet loosening under the centrifugal force generated by the high-speed rotation of the rotor.

[0004] Therefore, there is an urgent need in the market to develop an injection molding method for unsaturated resin that can achieve excellent adhesion between the rotor and the unsaturated resin material. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to develop an injection molding method for unsaturated resin that can give the rotor excellent adhesion.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides an injection molding method for a dry unsaturated thermosetting resin for an electric motor rotor, comprising the following steps: (1) Material preheating: The dry unsaturated polyester resin material is preheated by high frequency wave or injection molding machine to 85-95℃, so that it reaches a semi-softened state. (2) Mold preheating: After cleaning the mold, preheat the iron core and the upper and lower molds to 150-180℃; (3) Injection molding: The preheated material is fed into the feed port of the injection machine that has completed the heating or into the injection port of the injection molding machine, and it is injected into the mold cavity and covered with magnets; (4) Pressure holding and curing: The material in the mold cavity is subjected to pressure holding so that it is cured and formed in the mold.

[0007] In some implementations, when the equipment is started up or when the process conditions change, a temperature calibration step is included: the temperature of the lower end of the push rod of the transfer machine, the upper and lower molds and the iron core are measured to ensure that they are consistent with the set temperature, and then step three is performed.

[0008] This application develops a dry-type injection molding method for unsaturated thermosetting resins used in motor rotors. By preheating the unsaturated polyester material using high-frequency waves or an injection molding machine, a uniform and controllable softening state of the highly filled material is ensured before injection. This makes the unsaturated polyester material easier to fill in gaps, pores, and other minute spaces, thus improving the adhesion of the unsaturated polyester layer. This application achieves thermal equilibrium by preheating the iron core and mold together to 150-180°C, eliminating cold spots and ensuring that the materials solidify synchronously at similar rates, reducing internal stress and further improving dimensional stability and adhesion. Furthermore, this application enhances the stability and reliability of the process by limiting key process parameters (temperature, pressure, and time).

[0009] In some embodiments, the dry unsaturated polyester resin material comprises, by weight, the following components: 25-35 parts unsaturated polyester, 50-70 parts inorganic filler, 1-3 parts release agent, 0.8-1.2 parts peroxide curing agent, 0.5-1 part silane coupling agent, 20-30 parts reinforcing agent, and 0.5-1.5 parts surface pretreatment carbon black.

[0010] Preferably, the peroxide curing agent is tert-butyl peroxide.

[0011] This application uses the aforementioned dry unsaturated polyester resin material as a filler or adhesive for the gap between the connecting magnet and the iron core in a motor. This allows for multi-layer / integral injection molding in one step, improving production efficiency, reducing material waste, and significantly enhancing the rotor's temperature resistance, speed, NVH, and electrical performance.

[0012] In some embodiments, the mass ratio of the crystalline unsaturated polyester resin to the non-crystalline unsaturated polyester resin is 1:(3.2-3.6).

[0013] In some embodiments, the inorganic filler is one or more of aluminum hydroxide, calcium carbonate, and silica powder.

[0014] Preferably, the inorganic filler is a composition of aluminum hydroxide and silica powder, with a mass ratio of 1:(0.5-1.5).

[0015] Preferably, the aluminum hydroxide has a particle size of 5-15 μm, and the silicon micropowder has a particle size of 90-100 μm.

[0016] In some embodiments, the release agent is zinc stearate and / or calcium stearate.

[0017] In some embodiments, the silane coupling agent is one or more of KH-570, A-151, A-172, A-186, and Nanda-41.

[0018] Preferably, the silane coupling agent is A-186.

[0019] In some embodiments, the reinforcing agent is a composition of chopped glass fibers and glass fiber powder.

[0020] Preferably, the mass ratio of the chopped glass fiber to the glass fiber powder is 1:(0.3-0.6).

[0021] In some embodiments, the chopped glass fibers have a diameter of 10-12 μm and a length of 3-6 mm.

[0022] In some embodiments, the glass fiber powder has an average particle size of 800-1250 mesh.

[0023] In some embodiments, the preparation method of the surface pretreated carbon black includes the following steps: adding carbon black to tetrahydrofuran, ultrasonically treating for 50-70 min, adding p-chloromethylstyrene, purging with nitrogen for 20-40 min, adding azobisisobutyronitrile under nitrogen protection, heating to 65-75℃ and reacting for 12-24 h, cooling to room temperature, adding to methanol, stirring for 30-60 s, centrifuging and collecting the precipitate, washing with methanol and tetrahydrofuran alternately 3-5 times, and drying to obtain the surface pretreated carbon black.

[0024] In some embodiments, the mass ratio of the carbon black to p-chloromethylstyrene is 1:(1-5).

[0025] In some embodiments, the method for preparing the dry unsaturated polyester resin material includes the following steps: S1. Add solid unsaturated polyester, inorganic filler, silane coupling agent and release agent to a mixer and stir at room temperature for 5-10 minutes. Add surface pretreated carbon black and stir at room temperature for 5-10 minutes. Then add reinforcing agent and stir at low speed at room temperature for 1-2 minutes to obtain primary mixture. S2. The primary mixture obtained in step S1 is fed into the extruder at a constant speed via a feeder. The material is heated and softened in the extruder, then homogenized by the screw and pushed to the granulation die head. Granulation and cooling yield granulated unsaturated polyester material.

[0026] In some embodiments, the conditions for injection in step (3) are: injection pressure of 2-4 MPa and injection time of 10-50 s.

[0027] In some embodiments, the pressure holding conditions in step (4) are: pressure holding pressure of 2-3 MPa and pressure holding curing time of 75-150 s.

[0028] In some embodiments, the in-mold curing temperature in step (4) is 150-180°C.

[0029] In some embodiments, the semi-softened state has a firmness suitable for automated grasping and feeding by a robotic arm.

[0030] In some embodiments, the dry unsaturated polyester resin material further includes 0.5-1.5 parts by weight of a tackifier.

[0031] In some embodiments, the method for preparing the tackifier includes the following steps: A1. Add phenylphosphonic acid and tetrasodium vinyl diphosphonate to an ethanol aqueous solution, adjust the pH to 4-5, stir at room temperature for 20-30 minutes, and vacuum dry to obtain the synergist; A2. Add the synergist obtained in step S1 and one or two of p-benzoquinone or hydroquinone to diallyl phthalate, stir at room temperature for 10-20 minutes, then add KH-570 silane coupling agent, stir at room temperature for 10-20 minutes to obtain the thickener.

[0032] Preferably, the concentration of the ethanol aqueous solution is 85-95 wt%.

[0033] Preferably, the mass ratio of diallyl phthalate to p-benzoquinone in step A2 is 1:(0.015-0.025).

[0034] Preferably, the mass ratio of diallyl phthalate to hydroquinone in step A2 is 1:(0.03-0.035).

[0035] This application obtains an synergist by reacting phenylphosphonic acid and tetrasodium vinyl bisphosphonate. Then, a tackifier is obtained by compounding it with KH-570 silane coupling agent, diallyl phthalate, and p-benzoquinone or hydroquinone. Adding this tackifier to an unsaturated resin material system enhances the adhesion between the unsaturated resin and the iron core and magnets, increasing the magnet's pushing force. This improves the stability of the motor under high-speed rotation and drastic temperature changes. This is likely because: firstly, the tackifier system integrates the Si-OM bonding ability of silanes, the strong POM coordination ability of phosphonates, and the copolymerization ability of vinyl groups, exhibiting high reactivity with unsaturated polyester materials and strong bonding with magnets and iron cores; secondly, tetrasodium vinyl bisphosphonate contains multiple phosphate groups, which can chemically bond, complex, or hydrogen bond with inorganic fillers and reinforcing agents in the unsaturated polyester material, further enhancing its bonding with the unsaturated polyester material system. Meanwhile, the rigid benzene ring of phenylphosphonic acid enhances the rigidity and heat resistance of the interfacial layer, making the unsaturated polyester material less prone to detachment. Furthermore, diallyl phthalate, a crosslinking agent, can act as a bridging agent in the polymerization of unsaturated resins. Benzoquinone or hydroquinone acts as an inhibitor, effectively slowing down excessively rapid curing during the pouring process, thereby increasing fluidity and drilling ability, improving effective coating of the magnets, and thus enhancing adhesion. KH-570 silane coupling agent, an interfacial agent, increases the interfacial bonding between organic and inorganic components. The synergistic effect of these substances enhances the adhesion between the unsaturated resin and the iron core and magnets.

[0036] In some embodiments, the mass ratio of phenylphosphonic acid to tetrasodium vinyldiphosphonate is (0.5-1):1.

[0037] In some embodiments, the mass ratio of diallyl phthalate to synergist in step A2 is 1:(0.005-0.015).

[0038] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention develops an injection molding method for dry unsaturated thermosetting resin for motor rotors. By using high-frequency waves or injection molding machines to preheat the unsaturated polyester resin material, preheating the iron core and the mold together, and limiting key processes such as temperature, pressure, and time, the adhesion between the unsaturated polyester resin material and the iron core and magnets is improved.

[0039] 2. The present invention integrates the Si-OM bonding ability of silane, the strong POM coordination ability of phosphonate, and the copolymerization ability of vinyl groups into a tackifier obtained by compounding KH-570 silane coupling agent, phenylphosphonic acid and tetrasodium vinyl bisphosphonate. While having high reactivity with unsaturated polyester materials, it also has strong bonding force with iron cores and magnets, thereby further improving the adhesion of unsaturated resin to iron cores and magnets.

[0040] 3. The tackifier prepared by this invention contains multiple phosphate groups, which can chemically bond, complex, or hydrogen bond with inorganic fillers and reinforcing agents in unsaturated polyester materials, thereby further enhancing its bonding strength with the unsaturated polyester material system.

[0041] 4. The unsaturated polyester material obtained by mixing unsaturated polyester, mold release agent, curing agent, silane coupling agent, reinforcing agent, carbon black and tackifier has excellent mechanical properties and low molding shrinkage, which is beneficial to improving its adhesion to iron core and magnet. Detailed Implementation

[0042] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0043] In the following examples and comparative examples, except for the surface pretreatment carbon black, all other compounds and related reagents used were commercially available. The crystalline unsaturated polyester resin was a terephthalic crystalline unsaturated polyester, and the non-crystalline unsaturated polyester resin was an isophthalic non-crystalline unsaturated resin. The average particle size of aluminum hydroxide was 10 μm; the average particle size of silica powder was 95 μm; the diameter of chopped glass fibers was 11 μm and the length was 3 mm; the average particle size of glass fiber powder was 1000 mesh; the carbon black was type N-550; and the diameter of the iron core was 130 mm and the height was 150 mm.

[0044] Preparation Example 1 The preparation method of surface-pretreated carbon black includes the following steps: 1g of carbon black is added to 10ml of tetrahydrofuran, and ultrasonically treated for 60min at a power of 200W and a frequency of 30kHz. 2.5g of p-chloromethylstyrene is added, and nitrogen gas is introduced for 30min. Under nitrogen protection, 0.01g of azobisisobutyronitrile is added, and the mixture is heated to 70℃ and reacted for 18h. After cooling to room temperature, the mixture is added to 20ml of anhydrous methanol, stirred for 45s, and centrifuged at 9000rpm for 12min to collect the precipitate. The precipitate is washed 4 times alternately with anhydrous methanol and anhydrous tetrahydrofuran, and dried at 60℃ to obtain surface-pretreated carbon black.

[0045] Preparation Example 2 The preparation method of dry unsaturated polyester resin cake-1 includes the following steps: S1. By weight, add 30 parts of solid unsaturated polyester, 60 parts of inorganic filler, 0.7 parts of A-186 silane coupling agent, and 2 parts of zinc stearate to a mixer and stir at room temperature for 7 minutes. Then add 1 part of surface pretreated carbon black and 1 part of tert-butyl peroxide and stir at room temperature for 7 minutes. Finally, add 25 parts of reinforcing agent and stir at low speed at room temperature for 2 minutes to obtain the primary mixture. S2. The primary mixture obtained in step S1 is fed into the extruder at a constant speed via a feeder. The material is heated and softened in the extruder, then homogenized by the screw and pushed to the granulation die. Granulation and cooling yield granular unsaturated polyester material. The material temperature is 90°C and the extrusion die temperature is 95°C. S3. The granular unsaturated polyester material obtained in S2 is put into the patting machine, automatically weighed and pressed into patties, to obtain dry unsaturated polyester resin patty-1.

[0046] The unsaturated polyester is a composition of terephthalic crystalline unsaturated polyester resin and isophthalic amorphous unsaturated polyester resin, with a mass ratio of 1:3.4.

[0047] The inorganic filler is a composition of aluminum hydroxide and silica powder in a mass ratio of 1:1.

[0048] The reinforcing agent is a composition of chopped glass fibers and glass fiber powder in a mass ratio of 1:0.45.

[0049] Preparation Example 3 The preparation method of tackifier-1 includes the following steps: A1. Add 0.7g phenylphosphonic acid and 1g tetrasodium vinyldiphosphonate to 100ml 90wt% ethanol aqueous solution, adjust the pH to 5 with 0.1mol / L dilute hydrochloric acid, stir at room temperature for 25min, and dry under vacuum at 60℃ to constant weight to obtain the synergist. A2. Add 1.5g of the synergist obtained in step S1 and 3g of p-benzoquinone to 150g of diallyl phthalate, stir at room temperature for 15min, then add 1g of KH-570 silane coupling agent, stir at room temperature for 20min to obtain thickener-1.

[0050] Preparation Example 4 The preparation method of thickener-2 is the same as that of preparation example 1, except that the amount of phenylphosphonic acid added is 1.2g.

[0051] Preparation Example 5 The preparation method of tackifier-3 is the same as that of preparation example 1, except that the amount of synergist added is 2.55g.

[0052] Preparation Example 6 The preparation method of tackifier-4 includes the following steps: 3g of p-benzoquinone is added to 150g of diallyl phthalate and stirred at room temperature for 15min, then 1g of KH-570 silane coupling agent is added and stirred at room temperature for 20min to obtain tackifier-4.

[0053] Preparation Example 7 The preparation method of dry unsaturated polyester resin cake-2 includes the following steps: S1. By weight, add 30 parts of solid unsaturated polyester, 60 parts of inorganic filler, 0.7 parts of A-186 silane coupling agent, and 2 parts of zinc stearate to a mixer and stir at room temperature for 7 minutes. Add 1 part of tackifier-1, 1 part of surface pretreatment carbon black, and 1 part of tert-butyl peroxide and stir at room temperature for 7 minutes. Then add 25 parts of reinforcing agent and stir at low speed at room temperature for 2 minutes to obtain the primary mixture. S2. The primary mixture obtained in step S1 is fed into the extruder at a constant speed via a feeder. The material is heated and softened in the extruder, then homogenized by the screw and pushed to the granulation die. Granulation and cooling yield granular unsaturated polyester material. The material temperature is 90°C and the extrusion die temperature is 95°C. S3. The granular unsaturated polyester material obtained in S2 is put into the patting machine, automatically weighed and pressed into patties, to obtain dry unsaturated polyester resin patty-2.

[0054] The solid unsaturated polyester is a composition of terephthalic crystalline unsaturated polyester resin and isophthalic amorphous unsaturated polyester resin, with a mass ratio of 1:3.4.

[0055] The inorganic filler is a composition of aluminum hydroxide and silica powder in a mass ratio of 1:1.

[0056] The reinforcing agent is a composition of chopped glass fibers and glass fiber powder in a mass ratio of 1:0.45.

[0057] Preparation Example 8 The preparation method of dry unsaturated polyester resin cake-3 is the same as that of preparation example 7, except that tackifier-1 is replaced with tackifier-2 in equal amounts.

[0058] Preparation Example 9 The preparation method of dry unsaturated polyester resin cake-4 is the same as that of preparation example 7, except that tackifier-1 is replaced with tackifier-3 in equal amounts.

[0059] Preparation Example 10 The preparation method of dry unsaturated polyester resin cake-5 is the same as that of preparation example 7, except that tackifier-1 is replaced with tackifier-4 in equal amounts.

[0060] Example 1 An injection molding method for a dry unsaturated thermosetting resin for an electric motor rotor includes the following steps: (1) Preheating of cake material: 50g of dry unsaturated polyester resin cake material-2 is preheated by high frequency wave to 90℃, so that it reaches a softness and hardness suitable for automatic grasping and feeding by the robotic arm. (2) Mold preheating: After cleaning the mold, preheat the iron core and the upper and lower molds to 160°C; (3) Injection molding: The preheated cake material is put into the feeding port of the injection machine after the heating is completed. It is injected into the mold cavity and covered with magnets at an injection pressure of 3MPa. The injection time is 30s. (4) Pressure holding and curing: Under the set temperature and pressure, the material in the mold cavity is pressure held at 3MPa and the pressure holding and curing time is 120s, so that it is cured and formed in the mold. The curing temperature in the mold is 160℃.

[0061] Example 2 An injection molding method for a dry unsaturated thermosetting resin for an electric motor rotor includes the following steps: (1) Preheating of cake material: 50g of dry unsaturated polyester resin cake material-2 is preheated by high frequency wave to 85℃, so that it reaches a softness and hardness suitable for automatic grasping and feeding by the robotic arm. (2) Mold preheating: After cleaning the mold, preheat the iron core and the upper and lower molds to 150°C; (3) Injection molding: The preheated cake material is put into the feeding port of the injection machine after the heating is completed. It is injected into the mold cavity and covered with magnets at an injection pressure of 2MPa. The injection time is 50s. (4) Pressure holding and curing: Under the set temperature and pressure, the material in the mold cavity is pressure held at 2MPa and the pressure holding and curing time is 150s, so that it is cured and formed in the mold. The curing temperature in the mold is 150℃.

[0062] Example 3 An injection molding method for a dry unsaturated thermosetting resin for an electric motor rotor includes the following steps: (1) Preheating of cake material: 50g of dry unsaturated polyester resin cake material-2 is preheated by high frequency wave to 95℃, so that it reaches a softness and hardness suitable for automatic grasping and feeding by the robotic arm. (2) Mold preheating: After cleaning the mold, preheat the iron core and the upper and lower molds to 180°C; (3) Injection molding: The preheated cake material is put into the feeding port of the injection machine after the heating is completed. It is injected into the mold cavity and covered with magnets at an injection pressure of 4MPa. The injection time is 10s. (4) Pressure holding and curing: Under the set temperature and pressure, the material in the mold cavity is pressure held at 3MPa and the pressure holding and curing time is 90s, so that it is cured and formed in the mold. The curing temperature in the mold is 180℃.

[0063] Example 4 An injection molding method for a dry unsaturated thermosetting resin for an electric motor rotor is described. The specific implementation method is the same as in Example 1, except that the dry unsaturated polyester resin cake-2 is replaced with an equal amount of dry unsaturated polyester resin cake-1.

[0064] Example 5 An injection molding method for a dry unsaturated thermosetting resin for an electric motor rotor is described. The specific implementation method is the same as in Example 1, except that the dry unsaturated polyester resin cake-2 is replaced with an equal amount of dry unsaturated polyester resin cake-3.

[0065] Example 6 An injection molding method for a dry unsaturated thermosetting resin for an electric motor rotor is described. The specific implementation method is the same as in Example 1, except that the dry unsaturated polyester resin cake-2 is replaced with an equal amount of dry unsaturated polyester resin cake-4.

[0066] Example 7 An injection molding method for a dry unsaturated thermosetting resin for an electric motor rotor is described. The specific implementation method is the same as in Example 1, except that the dry unsaturated polyester resin cake-2 is replaced with an equal amount of dry unsaturated polyester resin cake-5.

[0067] Comparative Example 1 An injection molding method for a dry unsaturated thermosetting resin for an electric motor rotor includes the following steps: (1) Injection molding: 50g of dry unsaturated polyester resin cake-2 is put into the feed port of the injection machine, and it is injected into the mold cavity and covered with magnets at an injection pressure of 3MPa. The injection time is 30s. (2) Pressure holding and curing: Under the set temperature and pressure, the material in the mold cavity is pressure held at 3MPa and the pressure holding and curing time is 120s, so that it is cured and formed in the mold. The curing temperature in the mold is 160℃.

[0068] Performance testing The rotors coated with unsaturated polyester material obtained in the above embodiments and comparative examples were subjected to magnet push-out force performance tests. The testing machine was a universal testing machine with an accuracy requirement of 0.5 grade. The test results are shown in Table 1. Table 1

[0069] As can be seen from the data in Table 1, the rotors in Examples 1-3 have a high magnet pushing force, indicating that the dry unsaturated polyester resin cake in the rotor has good adhesion to the iron core and magnets after curing. The comparison between Example 4 and Example 1 shows that the magnet ejection force of the rotor injection molded using unsaturated polyester resin cake without tackifier is reduced; the comparison between Example 5 and Example 1 shows that changing the ratio of phenylphosphonic acid and tetrasodium vinyl bisphosphonate may make the interface brittle, thus leading to a decrease in the adhesion between the unsaturated polyester resin cake and the iron core and magnet, resulting in a decrease in the magnet ejection force of the rotor; the comparison between Example 6 and Example 1 shows that changing the ratio of diallyl phthalate and synergist may cause an excess of sodium salt to form a loose, hygroscopic salt residue layer at the interface. This layer has extremely low strength and becomes an inherently weak interface layer, resulting in a decrease in the adhesion between the unsaturated polyester resin cake and the iron core and magnet, thus reducing the magnet ejection force of the rotor; the comparison between Example 7 and Example 1 shows that the magnet ejection force of the rotor is reduced when the tackifier does not contain synergistic components; the comparison between Comparative Example 1 and Example 1 shows that the magnet ejection force of the rotor is low when no preheating is performed.

[0070] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method of injection molding a dry unsaturated thermoset resin for an electric motor rotor, characterized by, Includes the following steps: (1) Material preheating: The dry unsaturated polyester resin material is preheated by high frequency wave or injection molding machine to 85-95℃, so that it reaches a semi-softened state. (2) Mold preheating: After cleaning the mold, preheat the iron core and the upper and lower molds to 150-180℃; (3) Injection molding: The preheated material is fed into the feed port of the injection machine that has completed the heating or into the injection port of the injection molding machine, and it is injected into the mold cavity and covered with magnets; (4) Pressure holding and curing: The material in the mold cavity is subjected to pressure holding so that it is cured and formed in the mold.

2. The injection molding method for dry unsaturated thermosetting resin for motor rotors according to claim 1, characterized in that, The dry unsaturated polyester resin material, by weight, comprises the following components: 25-35 parts unsaturated polyester, 50-70 parts inorganic filler, 1-3 parts release agent, 0.8-1.2 parts peroxide curing agent, 0.5-1 part silane coupling agent, 20-30 parts reinforcing agent, and 0.5-1.5 parts surface pretreatment carbon black; wherein the unsaturated polyester is a composition of crystalline unsaturated polyester resin and non-crystalline unsaturated polyester resin.

3. The injection molding method for dry unsaturated thermosetting resin for motor rotors according to claim 2, wherein the preparation method of the dry unsaturated polyester resin material comprises the following steps: S1. Add solid unsaturated polyester, inorganic filler, silane coupling agent and release agent to a mixer and stir at room temperature for 5-10 minutes. Add surface pretreated carbon black and stir at room temperature for 5-10 minutes. Then add reinforcing agent and stir at low speed at room temperature for 1-2 minutes to obtain primary mixture. S2. The primary mixture obtained in step S1 is fed into the extruder at a constant speed via a feeder. The material is heated and softened in the extruder, then homogenized by the screw and pushed to the granulation die head. Granulation and cooling yield granulated unsaturated polyester material.

4. The injection molding method for dry unsaturated thermosetting resin for motor rotors according to claim 1, characterized in that, The conditions for injection in step (3) are: injection pressure of 2-4 MPa and injection time of 10-50 s.

5. The injection molding method for dry unsaturated thermosetting resin for motor rotors according to claim 1, characterized in that, The pressure holding conditions in step (4) are: pressure holding pressure is 2-3 MPa, and pressure holding curing time is 75-150 s.

6. The injection molding method for dry unsaturated thermosetting resin for motor rotors according to claim 1, characterized in that, The in-mold curing temperature in step (4) is 150-180℃.

7. The injection molding method for dry unsaturated thermosetting resin for motor rotors according to claim 2, characterized in that, The dry unsaturated polyester resin material also includes 0.5-1.5 parts by weight of a tackifier.

8. The injection molding method for dry unsaturated thermosetting resin for motor rotors according to claim 7, characterized in that, The method for preparing the thickener includes the following steps: A1. Add phenylphosphonic acid and tetrasodium vinyl diphosphonate to an ethanol aqueous solution, adjust the pH to 4-5, stir at room temperature for 20-30 minutes, and vacuum dry to obtain the synergist; A2. Add the synergist obtained in step S1 and one or two of p-benzoquinone or hydroquinone to diallyl phthalate, stir at room temperature for 10-20 minutes, then add KH-570 silane coupling agent, stir at room temperature for 10-20 minutes to obtain the thickener.

9. The injection molding method for dry unsaturated thermosetting resin for motor rotors according to claim 8, characterized in that, The mass ratio of phenylphosphonic acid to tetrasodium vinyldiphosphonate is (0.5-1):

1.

10. The injection molding method for dry unsaturated thermosetting resin for motor rotors according to claim 8, characterized in that, The mass ratio of diallyl phthalate to synergist in step A2 is 1:(0.005-0.015).

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