Lightweight high and low temperature resistant low pressure permanent magnet propulsion motor

Abstract

The application provides a high-low temperature and low pressure resistant lightweight permanent magnet propulsion motor, relates to the propulsion motor research and development field, and through analyzing the influence of the significant temperature change and air density reduction in different air spaces on the physical characteristics and heat dissipation performance of the motor material, the thermal expansion coefficient matching design is carried out on the stator assembly composed of the motor shell, the stator core and the armature winding, and the rotor assembly composed of the rotor sheath, the rotor core, the permanent magnet and the rotating shaft, and the high-low temperature resistant, low pressure resistant and lightweight collaborative optimization design is implemented. The application effectively guarantees the electromagnetic stability, mechanical reliability, heat dissipation capacity and electrical insulation performance of the propulsion motor under the high altitude and wide temperature range conditions.

Description

TECHNICAL FIELD

[0001] The application relates to the field of developing a propulsion motor, in particular to a lightweight high-low-temperature and low-pressure-resistant permanent magnet propulsion motor. BACKGROUND

[0002] The electrification of aircraft, low-altitude economy and unmanned aerial vehicle technology are jointly driving profound changes in the aviation field. Electric propulsion technology is gradually replacing traditional fossil fuels and becoming an efficient and clean power core. The rise of low-altitude economy has expanded diversified application scenarios and released broad development space. Intelligent unmanned aerial vehicles have achieved large-scale application in multiple fields due to their high autonomy and operational flexibility, and continue to extend to high-altitude, high-latitude, and even extremely cold and deep space. The technological changes in the aviation field are accelerating the construction of a new air operation system and jointly depicting the development blueprint of future transportation and industrial applications. Significant temperature changes and air density reduction in different airspaces (atmospheric space above the earth's surface) have important influences on the physical properties of motor materials, heat dissipation performance, corona discharge characteristics and electrical insulation performance. As one of the key core technologies of the propulsion system, the propulsion motor needs to have core performance indicators such as lightweight, high power density, wide temperature range and low pressure environment adaptability. SUMMARY

[0003] To solve the above technical problems, the application provides a lightweight high-low-temperature and low-pressure-resistant permanent magnet propulsion motor, which comprehensively considers the actual operating conditions of wide temperature range, low pressure, low air density, and takes into account the increasing demand for high-altitude flight endurance, with the core goal of realizing lightweight and high power density, and focuses on improving its adaptability in ultra-low temperature and low pressure environment. The application analyzes the influence of significant temperature changes and air density reduction in different airspaces on the physical properties of motor materials and heat dissipation performance; for the stator assembly composed of a machine shell, a stator core and an armature winding, and the rotor assembly composed of a rotor sheath, a rotor core, a permanent magnet and a rotating shaft, respectively, the thermal expansion coefficient matching design is carried out, and the high-low-temperature-resistant, low-pressure-resistant and lightweight collaborative optimization design is implemented, which effectively guarantees the electromagnetic stability, mechanical reliability, heat dissipation capacity and electrical insulation performance of the motor under high-altitude and wide temperature range conditions, and finally realizes a high-performance and high-reliability permanent magnet propulsion system.

[0004] To achieve the above purpose, the application adopts the following technical solutions:

[0005] The application discloses a high and low temperature resistant and low pressure light-weight permanent magnet propulsion motor, which comprises a stator assembly and a rotor assembly; the stator assembly comprises a titanium alloy motor shell, an ultra-thin non-oriented silicon steel sheet stator core and an armature winding, and the rotor assembly comprises a titanium alloy hollow rotating shaft, a cobalt-iron alloy rotor core, a samarium-cobalt permanent magnet and a carbon fiber composite sheath; the titanium alloy motor shell and the ultra-thin non-oriented silicon steel sheet stator core have a difference of not more than a reference threshold value in the medium value of thermal expansion coefficients, the cobalt-iron alloy rotor core, the samarium-cobalt permanent magnet and the titanium alloy hollow rotating shaft have a difference of not more than the reference threshold value in the medium value of thermal expansion coefficients; the carbon fiber composite sheath is wrapped around the periphery of the cobalt-iron alloy rotor core to form a radial pre-tightening constraint; an ammonia-ethane working medium capillary core low-temperature heat pipe extends from the ultra-thin non-oriented silicon steel sheet stator core to the inside of the titanium alloy motor shell; the ultra-thin non-oriented silicon steel sheet stator core and the titanium alloy motor shell, the ammonia-ethane working medium capillary core low-temperature heat pipe and the ultra-thin non-oriented silicon steel sheet stator core, the samarium-cobalt permanent magnet and the cobalt-iron alloy rotor core, the carbon fiber composite sheath and the cobalt-iron alloy rotor core and the titanium alloy hollow rotating shaft and the cobalt-iron alloy rotor core are fixedly connected through interference fit, adhesion or welding.

[0006] Further, the reference threshold value is 1.5*10 -6 / ℃; the silicon steel sheets of the ultra-thin non-oriented silicon steel sheet stator core are coated with a high-performance composite coating containing nanoparticles, a size chain is established between the stator core and the titanium alloy motor shell, an interference fit is formed at room temperature and the tight fit is still maintained at the lowest working temperature, and the interface gap between the two is filled with modified epoxy resin thermal conductive glue containing boron nitride.

[0007] Further, the flat copper wire armature winding adopts polyimide-nano ceramic composite insulation wrapping wire, and is filled with low-temperature-resistant and high-toughness modified polyester impregnated varnish through a dynamic vacuum pressure impregnation process; a thin film thermocouple based on MEMS technology and a heating element are pre-embedded in the winding, so that real-time monitoring and closed-loop regulation of temperature are realized.

[0008] Further, the titanium alloy motor shell is provided with a plurality of radial radiating fins, the surface of the radial radiating fins is subjected to laser texturing treatment and is subjected to plasma spraying of an alumina-titania composite ceramic coating.

[0009] Further, the ammonia-ethane working medium capillary core low-temperature heat pipe is inserted into the ultra-thin non-oriented silicon steel sheet stator core in an interference fit mode and is fixed through brazing, and the interface gap between the heat pipe and the ultra-thin non-oriented silicon steel sheet stator core is filled with modified epoxy resin thermal conductive glue containing boron nitride.

[0010] Further, the connection interface between the carbon fiber composite sheath and the cobalt-iron alloy rotor core is filled with a high-toughness low-temperature epoxy adhesive.

[0011] Further, the pieces of the cobalt-iron alloy rotor core are bonded together and aligned by the aluminum alloy rods penetrating through the through holes, and the aluminum alloy rods are connected with the aluminum alloy end plates by friction stir welding to form an integrated structure.

[0012] Further, the samarium-cobalt permanent magnets are embedded in the clamping slots of the cobalt-iron alloy rotor core in a built-in uniform segmented structure, the gaps between the samarium-cobalt permanent magnets and between the samarium-cobalt permanent magnets and the cobalt-iron alloy rotor core are filled with high-toughness low-temperature epoxy adhesive, and the samarium-cobalt permanent magnets and the clamping slots are assembled by forming an interference fit at room temperature and still maintaining a tight fit at the lowest working temperature.

[0013] Further, the titanium alloy hollow shaft and the cobalt-iron alloy rotor core are combined by a spline coupling and high-toughness low-temperature epoxy adhesive.

[0014] Further, the modified epoxy resin thermal conductive adhesive containing boron nitride and the high-toughness low-temperature epoxy adhesive are uniformly coated by high-precision quantitative non-contact dispensing process to realize the minimization of the amount of adhesive at the interface.

[0015] Beneficial effects:

[0016] 1. In the conventional motor structure design, the thermal expansion coefficient (CTE) matching is usually not fully considered. The present application separately designs the thermal expansion coefficient matching of the stator assembly and the rotor assembly of the propulsion motor, fills the modified epoxy resin thermal conductive adhesive containing boron nitride at each connecting part of the stator assembly to enhance the thermal conductivity between the interfaces, and fills the high-toughness low-temperature epoxy adhesive at each connecting part of the rotor assembly to buffer the stress generated during thermal expansion and contraction. In the material selection process of the motor casing, stator, sheath, rotor and permanent magnet, although similar materials only have slight performance differences between different models, the thermal expansion coefficient is not only closely related to the material composition, but also affected by the length, thickness and surface treatment process of the material. Therefore, the present application particularly emphasizes fine material selection, and preferentially selects similar materials with a difference of no more than 1.5 x 10 -6 / ℃ in the median value of the thermal expansion coefficient. For parts with larger temperature difference changes and larger volumes or sizes, the difference in the median value of the thermal expansion coefficient is required to be further reduced. The thermal expansion coefficient (CTE) matching design adopts a preventive concept to inhibit structural problems caused by thermal expansion and contraction mismatch from the source of the material, thereby improving the reliability, service life and performance stability of the product in a temperature change environment, which is rarely mentioned in conventional motor design.

[0017] 2. In the traditional motor design, the influence of ultra-low temperature environment on the performance of heat transfer working medium in heat pipe is rarely considered. The ammonia-ethane mixed working medium capillary core low-temperature heat pipe is adopted, the temperature range of the working medium can fully cover the ultra-low temperature operation condition of the propulsion motor, and the temperature application range of the conventional heat pipe is limited; the heat pipe is driven by capillary force and is not limited by the direction of gravity, and is suitable for the working environment of aircraft with variable attitude. The low-temperature heat pipe and the stator core are connected by a composite fixing mode combining interference fit, brazing and adhesion, wherein the interference fit and brazing provide extremely low thermal resistance and high structural strength, and can effectively withstand the vibration and impact load generated during flight; at the same time, the modified epoxy resin thermal conductive adhesive containing boron nitride is used to fill the small interface gap, further reducing the contact thermal resistance and significantly improving the overall heat conduction performance.

[0018] 3. The stator core of the general motor adopts ordinary insulation coating, while in the present application, the stator core adopts a high-performance composite coating containing nanoparticles coated on the surface of ultra-thin non-oriented silicon steel sheet. The composite coating has excellent electrical insulation performance and high temperature stability, the nanoparticles can effectively fill the micro pores in the coating, forming a more dense and defect-free insulation layer, significantly improving the breakdown field strength; at the same time, it can capture and bind high-energy electrons, inhibit the initiation and development of partial discharge, delay the aging process of the insulation material, and significantly enhance the wear resistance and mechanical strength of the coating.

[0019] 4. Between the ultra-thin non-oriented silicon steel sheet stator core and the titanium alloy shell, and between the clamping slot of the samarium-cobalt permanent magnet and the cobalt-iron alloy rotor core, a size chain is constructed to achieve interference fit at room temperature and maintain moderate tight fit at the lowest working temperature, ensuring that the magnet does not loosen at full working temperature range. The samarium-cobalt permanent magnet has high hardness and brittleness characteristics, which can be smoothly pressed into the hydraulic press during room temperature assembly, effectively avoiding the introduction of initial micro-cracks in the magnet, and preventing the expansion of macro-cracks under thermal stress.

[0020] 5. The titanium alloy motor shell adopted in the present application has high strength, low density and excellent environmental corrosion resistance, and more importantly, its thermal expansion coefficient is similar to that of the non-oriented silicon steel sheet stator core, which can significantly reduce the thermal deformation difference between the two under conditions of rapid temperature change, thereby effectively reducing the interfacial thermal stress and preventing the fit from loosening.

[0021] 6. Ordinary insulating varnish is prone to embrittlement in ultra-low temperature environments. The flat copper wire armature winding in this invention is superior to traditional enameled wire in terms of insulation thickness, withstand voltage rating, heat resistance, and mechanical strength. The polyimide-nano-ceramic composite insulation material possesses excellent toughness in ultra-low temperature ranges, making it more suitable for high-altitude flight propulsion systems. The polyimide-insulated flat copper wire has a further thinner insulation layer than traditional winding processes. The combination of flat copper wire and ultra-thin insulation layer is particularly suitable for the design requirements of high-power-density motors, enabling higher slot fill factor and space utilization. Through dynamic vacuum pressure impregnation rather than static vacuum pressure impregnation, the low-temperature resistant and high-toughness modified polyester impregnation varnish continuously re-penetrates into nearby gaps or defects as the motor stator rotates slowly, significantly improving the quality of the winding impregnation and providing superior comprehensive protection against moisture, condensation, corrosion, and vibration. Compared to traditional thermocouples, thin-film thermocouples based on MEMS (Micro-Electro-Mechanical Systems) technology can be directly integrated into the inner wall of the motor housing or the surface of key components due to their ultra-thin characteristics, achieving near-interference-free in-situ temperature measurement.

[0022] 7. In common motor designs, carbon fiber composite sheaths are typically used to fix surface-mounted permanent magnets; however, the carbon fiber composite sheath in this invention is used to wrap around the cobalt-iron alloy rotor core to form a stable radial preload constraint. This sheath has a near-zero or even negative coefficient of thermal expansion, and under conditions of drastic temperature changes, it can continuously apply a stable radial preload force to the internal cobalt-iron alloy core and permanent magnets, effectively ensuring structural integrity and operational reliability.

[0023] 8. Compared with traditional non-oriented silicon steel, using cobalt-iron alloy as the rotor core material for motors can significantly improve the power density and output torque of the motor due to its saturation magnetization intensity reaching over 2.4 T, which is beneficial for the lightweight design of aircraft propulsion systems. Simultaneously, this material exhibits excellent high and low temperature stability over a wide temperature range; some cobalt-iron alloys maintain good strength and ductility even at temperatures ranging from -150°C to higher. Furthermore, the cobalt-iron alloy rotor core is fixed using a three-in-one forming method: piece-by-piece bonding, circumferential fixing with aluminum alloy rods, and axial welding fixing with aluminum alloy end plates. This effectively prevents structural deformations such as localized springback and bow-shaped bulges caused by temperature changes.

[0024] 9. Samarium cobalt permanent magnets exhibit superior high and low temperature resistance compared to neodymium iron boron permanent magnets. Furthermore, by dividing the overall magnetic pole into multiple small magnetic blocks with minute gaps between adjacent blocks, and filling these gaps with a high-toughness adhesive possessing elastic and low-temperature resistant properties, an elastic buffer layer is formed. This structure provides a buffer space for the magnet's thermal expansion and contraction under varying temperature conditions, effectively preventing stress accumulation within the overall magnet, achieving localized stress release, and preventing magnet cracking.

[0025] 10、The titanium alloy rotating shaft material density is low, and the tensile strength can reach 960 MPa or more, the high specific strength characteristics make the prepared hollow rotating shaft realize the effect of significant light weight under the premise of meeting the mechanical strength and rigidity requirements; the spline connection and the combined assembly scheme of the adhesive connection between the rotating shaft and the cobalt-iron alloy rotor core effectively guarantee the mechanical stability of the assembly interface under the variable temperature working condition.

[0026] 11、The traditional gluing process is difficult to accurately control the gluing amount and the gluing thickness, the high-precision quantitative non-contact injection dispensing process is adopted to realize uniform coating, which effectively improves the heat conduction performance and high and low temperature resistance, and realizes the minimum use of glue at the interface. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a structure diagram of a high and low temperature resistant light weight permanent magnet propulsion motor;

[0028] Figure 2 It is a structure diagram of a permanent magnet propulsion motor stator assembly;

[0029] Figure 3 It is a structure diagram of a permanent magnet propulsion motor rotor assembly;

[0030] Among them, the reference signs are: titanium alloy motor shell 1, ultra-thin non-oriented silicon steel sheet stator core 2, carbon fiber composite material sheath 3, cobalt-iron alloy rotor core 4, samarium-cobalt permanent magnet 5, titanium alloy hollow rotating shaft 6, ammonia-ethane working medium capillary core low temperature heat pipe 7, aluminum alloy rod 8, aluminum alloy end plate 9, flat copper wire armature winding 10, radial radiation heat sink fin 11. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present application clearer, the following will be further described in detail in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other. The present application will be specifically described below in combination with the drawings.

[0032] As Figures 1-3As shown, the lightweight high and low temperature resistant low pressure permanent magnet propulsion motor of the application is designed for the coefficient of thermal expansion matching design between the interfaces of the titanium alloy motor shell 1, the ultra-thin non-oriented silicon steel sheet stator core 2, the carbon fiber composite sheath 3, the cobalt-iron alloy rotor core 4, the samarium-cobalt permanent magnet 5, and the titanium alloy hollow rotating shaft 6. The material selection and connection structure of the titanium alloy motor shell 1, the ultra-thin non-oriented silicon steel sheet stator core 2, the carbon fiber composite sheath 3, the cobalt-iron alloy rotor core 4, the samarium-cobalt permanent magnet 5, the titanium alloy hollow rotating shaft 6, and the flat copper wire armature winding 10 are cooperatively optimized in high and low temperature resistance, low pressure resistance, and lightweight.

[0033] The lightweight high and low temperature resistant low pressure permanent magnet propulsion motor of the application includes a titanium alloy motor shell 1, an ultra-thin non-oriented silicon steel sheet stator core 2, a carbon fiber composite sheath 3, a cobalt-iron alloy rotor core 4, a samarium-cobalt permanent magnet 5, a titanium alloy hollow rotating shaft 6, an ammonia-ethane working medium capillary core low temperature heat pipe 7, an aluminum alloy rod 8, an aluminum alloy end plate 9, a flat copper wire armature winding 10, and a radiating heat sink fin 11. The samarium-cobalt permanent magnet 5 is embedded in the clamping groove of the cobalt-iron alloy rotor core 4 in a built-in uniform segmented structure, the cobalt-iron alloy rotor core 4 is composite assembled with the titanium alloy hollow rotating shaft 6 through high toughness low temperature epoxy adhesive bonding and spline coupling, and the carbon fiber composite sheath 3 is wrapped around the outer periphery of the cobalt-iron alloy rotor core 4 to form radial pre-tightening constraint. The ammonia-ethane working medium capillary core low temperature heat pipe 7 is inserted into the ultra-thin non-oriented silicon steel sheet stator core 2 in an interference fit manner and is fixed by brazing. The ammonia-ethane working medium capillary core low temperature heat pipe 7 extends from the ultra-thin non-oriented silicon steel sheet stator core 2 to the inside of the titanium alloy motor shell 1. The ultra-thin non-oriented silicon steel sheet stator core 2 and the titanium alloy motor shell 1 are connected by interference fit and nitrogen-containing boron modified epoxy resin heat conducting adhesive bonding. The surface of the titanium alloy motor shell 1 is provided with the radiating heat sink fin 11. The pieces of the cobalt-iron alloy rotor core 4 are bonded by piece-by-piece bonding, aligned by the aluminum alloy rod 8 penetrating through the through holes, and connected and fixed by friction stir welding at both ends of the aluminum alloy rod 8 and the aluminum alloy end plate 9. The flat copper wire armature winding 10 is sequentially embedded in the stator slots of the ultra-thin non-oriented silicon steel sheet stator core 2.

[0034] Further, the thermal expansion coefficient matching design enables the materials in the stator assembly and the rotor assembly to expand and contract in coordination during temperature changes. The stator assembly (including the titanium alloy motor housing 1, the ultra-thin non-oriented silicon steel sheet stator core 2, and the flat copper wire armature winding 10) is matched and combined by the titanium alloy motor housing 1 and the ultra-thin non-oriented silicon steel sheet stator core 2, whose median values of the thermal expansion coefficients differ by no more than a reference threshold. The rotor assembly (including the carbon fiber composite sheath 3, the cobalt-iron alloy rotor core 4, the samarium-cobalt permanent magnet 5, and the titanium alloy hollow rotating shaft 6) is matched and combined by the cobalt-iron alloy rotor core 4, the samarium-cobalt permanent magnet 5, and the titanium alloy hollow rotating shaft 6, whose median values of the thermal expansion coefficients differ by no more than a reference threshold, and the carbon fiber composite sheath 3 is used to radially pre-tighten and constrain the entire rotor assembly.

[0035] Preferably, the reference threshold is 1.5×10 -6 / ℃.

[0036] Further, the titanium alloy motor housing 1 includes an ammonia-ethane working medium capillary core low-temperature heat pipe 7 extending from the ultra-thin non-oriented silicon steel sheet stator core 2 to the inside of the titanium alloy motor housing 1. The outer surface of the titanium alloy motor housing 1 is provided with a plurality of radiating fins 11 to increase the effective heat dissipation area. The radiating fins 11 are laser textured and plasma sprayed with an alumina-titania composite ceramic coating to enhance the convective heat transfer coefficient and the radiation heat dissipation capacity. A size chain (i.e. a tolerance fit, including all interference, transition, and gap fit cases) is established between the ultra-thin non-oriented silicon steel sheet stator core 2 and the titanium alloy motor housing 1 to ensure an interference fit at room temperature and maintain a moderate tight fit state at the lowest working temperature, and a modified epoxy resin thermal conductive glue containing boron nitride is filled in the gap between them to enhance the thermal conductivity between the interfaces.

[0037] Further, the silicon steel sheets of the ultra-thin non-oriented silicon steel sheet stator core 2 of the stator assembly are coated with a high-performance composite coating containing nanoparticles. The ammonia-ethane working medium capillary core low-temperature heat pipe 7 is inserted into the ultra-thin non-oriented silicon steel sheet stator core 2 in an interference fit and fixed by brazing, and the interface gap is filled with a modified epoxy resin thermal conductive glue containing boron nitride to reduce the contact thermal resistance.

[0038] Further, the flat copper wire armature winding 10 uses a cold and heat shock resistant polyimide-nano ceramic composite insulation wrapping wire, and in a slow rotation dynamic vacuum pressure impregnation process, a low-temperature resistant and high-toughness modified polyester impregnating varnish is selected to avoid low-temperature embrittlement risk, prevent corona, and enhance electrical insulation. Thin film thermocouples and heating elements based on MEMS technology are pre-embedded in key parts such as windings and bearings to realize real-time monitoring and closed-loop regulation of temperature, and pre-heating control is implemented during the cold start stage to ensure safe and reliable operation of the equipment.

[0039] Further, the carbon fiber composite material sheath 3 is wrapped around the outer periphery of the cobalt-iron alloy rotor core 4 to form radial pre-tightening constraints, and high-toughness low-temperature epoxy adhesives are filled at the connecting interfaces to compensate for assembly gaps and relieve stress caused by thermal expansion and contraction. In a low-temperature environment, the shrinkage degree of the internal cobalt-iron alloy rotor core 4 is slightly greater than that of the carbon fiber composite material sheath 3, but the radial pre-tightening force generated by the carbon fiber composite material sheath 3 and the bonding force generated by the adhesives can still effectively prevent separation of the two interfaces; in a high-temperature condition, the carbon fiber composite material sheath 3 can effectively inhibit the excessive expansion of the metal components, thereby maintaining the integrity of the overall structure.

[0040] Further, the rotor assembly adopts a three-in-one forming process of piece-by-piece bonding, aluminum alloy rod 8 circumferential fixation, and aluminum alloy end plate 9 axial welding fixation. The pieces of the cobalt-iron alloy rotor core 4 are bonded piece by piece, aligned through the through holes of the aluminum alloy rod 8, and the two ends of the aluminum alloy rod 8 are connected and fixed with the aluminum alloy end plate 9 by friction stir welding. After welding, the aluminum alloy rod 8 and the aluminum alloy end plate 9 form an integrated structure, achieving axial and circumferential positioning of the rotor assembly and significantly improving the structural stability of the rotor assembly under temperature changes.

[0041] Further, the samarium-cobalt permanent magnet 5 adopts an embedded uniform segmented permanent magnet structure. The samarium-cobalt permanent magnet 5 is segmented and embedded into the clamping slots of the cobalt-iron alloy rotor core 4, and high-toughness low-temperature epoxy adhesives are used to fill the gaps between the samarium-cobalt permanent magnets 5 and between the samarium-cobalt permanent magnets 5 and the cobalt-iron alloy rotor core 4 to buffer thermal expansion and contraction stress. Based on the lowest working temperature condition, the size changes of the samarium-cobalt permanent magnet 5 and the clamping slots during thermal expansion and contraction are accurately calculated to construct a size chain that is an interference fit at room temperature and still maintains a moderate tight fit at the lowest working temperature. During assembly, the cobalt-iron alloy rotor core 4 is heated appropriately, and the samarium-cobalt permanent magnet 5 is cooled at the same time. By using the principle of thermal fit, the samarium-cobalt permanent magnet 5 is smoothly and uniformly pressed into the clamping slots by a hydraulic press.

[0042] Further, the titanium alloy hollow shaft 6 and the cobalt-iron alloy rotor core 4 are combined by spline coupling and high-toughness low-temperature epoxy adhesive bonding to ensure the mechanical stability of the assembly interface under temperature changes.

[0043] Embodiment:

[0044] As shown in Figure 1 , for a titanium alloy (TC4 Ti-6Al-4V, thermal expansion coefficient (9.0~9.8)×10 -6 / ℃) motor housing 1 and an ultra-thin non-oriented silicon steel sheet stator core 2 (thickness ≤0.1mm, thermal expansion coefficient (10.0~11.2)×10 -6 / ℃), carbon fiber composite sheath 3 (carbon fiber reinforced CF / PEEK, thermal expansion coefficient (8.8~9.5) x 10 -6 / ℃) and cobalt-iron alloy (1J22 Hiperco 50, thermal expansion coefficient (8.7~9.6) x 10 -6 / ℃) rotor core 4, cobalt-iron alloy rotor core 4 and samarium-cobalt (2:17 type sm2co 17 , thermal expansion coefficient (9.7~10.5) x 10 -6 / ℃) permanent magnet 5, cobalt-iron alloy rotor core 4 and titanium alloy (TC4 Ti-6Al-4V, thermal expansion coefficient (9.0~9.8) x 10 -6 / ℃) hollow shaft 6 are designed to match the thermal expansion coefficients; and the titanium alloy motor housing 1, the ultra-thin non-oriented silicon steel sheet stator core 2, the carbon fiber composite sheath 3, the cobalt-iron alloy rotor core 4, the samarium-cobalt permanent magnet 5, the titanium alloy hollow shaft 6 and the flat copper wire armature winding 10 are designed to match the thermal expansion coefficients.

[0045] In the thermal expansion coefficient matching design, the materials are designed to expand and contract cooperatively during temperature changes. The stator assembly is matched and combined by the titanium alloy motor housing 1 and the ultra-thin non-oriented silicon steel sheet stator core 2, whose thermal expansion coefficients differ by no more than 1.5 x 10 -6 / ℃. The rotor assembly is matched and combined by the cobalt-iron alloy rotor core 4, the samarium-cobalt permanent magnet 5 and the titanium alloy hollow shaft 6, whose thermal expansion coefficients differ by no more than 1.5 x 10 -6 / ℃, and the entire rotor assembly is radially pre-tightened and constrained by the carbon fiber composite sheath 3. Assuming that the temperature difference of the working environment of the propulsion motor changes by 200℃, when the length of a part in a certain direction is 50mm and the thermal expansion coefficients differ by 1.5 x 10 -6 / ℃, the difference between the expansion and contraction amounts of the two materials is The calculation formula is:

[0046] ;

[0047] From The calculation formula shows that the greater the temperature difference change and the larger the size of the part, the more significant the size change during thermal expansion and contraction. Therefore, when designing the thermal expansion coefficient matching for large-size parts or working conditions that experience greater temperature changes, the difference between the thermal expansion coefficients of the materials should be further reduced, possibly to less than 1.5 x 10 -6 / ℃, to ensure that the difference between the thermal expansion and contraction amounts of the two materials does not exceed the allowed range of interference fit, preventing interference connection failure. The difference between the thermal expansion coefficients of the materials in the present application is 1.5 x 10 -6℃ is only a reference threshold in most cases, and does not constitute a limitation on the scope of protection of the present application. In addition, the modified epoxy resin thermal conductive adhesive containing boron nitride is filled in each connecting part of the stator assembly, and the high-toughness low-temperature epoxy adhesive is filled in each connecting part of the rotor assembly, which can effectively buffer the stress generated in the process of thermal expansion and cold contraction, and is an indispensable technical link in the matching design of the thermal expansion coefficient, which helps to improve the overall matching effect.

[0048] As shown in Figure 2 In the optimization design of the titanium alloy motor shell 1, the ammonia-ethane working medium (ammonia temperature range -73℃~127℃, ethane temperature range -153℃~27℃) capillary core low-temperature heat pipe 7 extends from the ultra-thin non-oriented silicon steel sheet stator core 2 to the inside of the titanium alloy motor shell 1, and the outer surface of the shell is provided with a plurality of radial radiation fins 11 to increase the effective heat dissipation area. The radial radiation fins 11 are subjected to laser surface texturing and plasma spraying of aluminum oxide-titanium dioxide (Al2O3-TiO2) composite ceramic coating to enhance the convective heat transfer coefficient and radiation heat dissipation capacity; a size chain is established between the ultra-thin non-oriented silicon steel sheet stator core 2 and the titanium alloy motor shell 1 to ensure that an interference fit is formed at room temperature and a moderate tight fit is maintained at the lowest working temperature, and a modified epoxy resin thermal conductive adhesive containing boron nitride (3M TC-2810 / EPO-TEK 930-4) is filled in the gap between the two interfaces to enhance the thermal conductivity between the interfaces.

[0049] In the optimization design of the ultra-thin non-oriented silicon steel sheet stator core 2 of the motor, a high-performance composite coating containing nano particles (SiO2 / Al2O3) is coated between the silicon steel sheets of the ultra-thin non-oriented silicon steel sheet stator core 2; the ammonia-ethane working medium capillary core low-temperature heat pipe 7 is inserted into the ultra-thin non-oriented silicon steel sheet stator core 2 in an interference fit manner and is fixed by brazing, and a modified epoxy resin thermal conductive adhesive containing boron nitride is filled in the gap between the interfaces to reduce the contact thermal resistance.

[0050] In the optimization design of the flat copper wire armature winding 10, the flat copper wire armature winding 10 uses a cold and hot impact resistant polyimide-nano ceramic composite insulation wrapped wire, and in the dynamic vacuum pressure impregnation process, a low-temperature resistant and high-toughness modified polyester impregnating varnish (Desmophen 7650) is selected to avoid the risk of low-temperature embrittlement, prevent corona and enhance electrical insulation; a thin film thermocouple and a heating element based on MEMS technology are pre-embedded in key parts such as the winding and the bearing to realize real-time monitoring and closed-loop regulation of temperature, and pre-heating control is implemented during the cold start stage to ensure safe and reliable operation of the equipment.

[0051] In the optimization design of the carbon fiber composite sheath 3, the carbon fiber composite sheath 3 is wrapped around the cobalt-iron alloy rotor core 4 to form radial pre-tightening constraint, and high-toughness low-temperature epoxy adhesive (Supreme 12AOHT-LO / EP29LPSP) is filled at the connecting interface to compensate for the assembly gap and relieve the stress caused by thermal expansion and cold contraction. In a low-temperature environment, the shrinkage degree of the internal metal components is slightly greater than that of the carbon fiber composite sheath 3, but the radial pre-tightening force generated by the carbon fiber composite sheath 3 and the bonding force generated by the adhesive can still effectively prevent the separation of the interface; in a high-temperature condition, the carbon fiber composite sheath 3 can effectively inhibit the excessive expansion of the metal components, thereby maintaining the integrity of the overall structure.

[0052] As shown in Figure 3 In the optimization design of the motor cobalt-iron alloy rotor core 4, a three-in-one forming process of piece-by-piece bonding, aluminum alloy rod 8 circumferential fixation and aluminum alloy end plate 9 axial welding fixation is adopted. The pieces of the cobalt-iron alloy rotor core 4 are bonded piece by piece, aligned through the through holes of the aluminum alloy (7075-T6) rods 8, and the two ends of the aluminum alloy rods 8 are connected and fixed with the aluminum alloy (7075-T6) end plates 9 by friction stir welding. After welding, the aluminum alloy rods 8 and the aluminum alloy end plates 9 form an integrated structure, achieving axial and circumferential positioning of the rotor assembly and significantly improving the structural stability of the rotor assembly under temperature changes.

[0053] In the optimization design of the samarium-cobalt permanent magnet 5, a built-in uniform segmented permanent magnet structure is adopted, the samarium-cobalt permanent magnet 5 is segmented and embedded in the clamping groove of the cobalt-iron alloy rotor core 4, and high-toughness low-temperature epoxy adhesive is selected to fill the gaps between the samarium-cobalt permanent magnets 5 and between the samarium-cobalt permanent magnets 5 and the cobalt-iron alloy rotor core 4 to buffer the thermal expansion and cold contraction stress. Based on the lowest working temperature condition, the size changes of the samarium-cobalt permanent magnet 5 and the clamping groove during thermal expansion and cold contraction are accurately calculated to construct a size chain that is an interference fit at room temperature and still maintains a moderate tight fit at the lowest working temperature. During assembly, the cobalt-iron alloy rotor core 4 is heated appropriately, and the samarium-cobalt permanent magnet 5 is cooled at the same time. By using the principle of thermal fit, the samarium-cobalt permanent magnet 5 is smoothly and uniformly pressed into the clamping groove by a hydraulic press.

[0054] In the optimization design of the motor titanium alloy hollow shaft 6, a composite assembly scheme combining spline coupling and high-toughness low-temperature epoxy adhesive bonding is adopted between the titanium alloy hollow shaft 6 and the cobalt-iron alloy rotor core 4 to ensure the mechanical stability of the assembly interface under temperature changes.

[0055] The modified epoxy resin heat-conducting adhesive containing boron nitride and the high-toughness low-temperature epoxy adhesive are uniformly coated by using high-precision quantitative non-contact jet dispensing process, which effectively improves the heat-conducting performance and the high and low temperature resistance performance, ensures that the adhesive amount of the interface is close to the minimum, and solves the contradiction faced by the aircraft propulsion motor in the lightweight design: on the one hand, the heat-conducting adhesive needs to be coated to enhance the heat dissipation performance under the condition of high altitude and low air density, on the other hand, the high-toughness epoxy adhesive needs to be filled to buffer thermal stress under wide temperature range operation, but both of them are easy to cause weight increase.

[0056] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure, characterized in that, The system includes a stator assembly and a rotor assembly. The stator assembly comprises a titanium alloy motor housing, an ultra-thin non-oriented silicon steel sheet stator core, and an armature winding. The rotor assembly comprises a titanium alloy hollow shaft, a cobalt-iron alloy rotor core, a samarium-cobalt permanent magnet, and a carbon fiber composite sheath. The median difference in the coefficient of thermal expansion between the titanium alloy motor housing and the ultra-thin non-oriented silicon steel sheet stator core does not exceed a reference threshold. The median difference in the coefficient of thermal expansion between the cobalt-iron alloy rotor core, the samarium-cobalt permanent magnet, and the titanium alloy hollow shaft does not exceed a reference threshold. The carbon fiber composite sheath encases the cobalt-iron alloy... A radial pre-tight constraint is formed around the rotor core; the ammonia-ethane working fluid capillary core low-temperature heat pipe extends from the ultra-thin non-oriented silicon steel sheet stator core to the interior of the titanium alloy motor housing; the ultra-thin non-oriented silicon steel sheet stator core and the titanium alloy motor housing, the ammonia-ethane working fluid capillary core low-temperature heat pipe and the ultra-thin non-oriented silicon steel sheet stator core, the samarium cobalt permanent magnet and the cobalt iron alloy rotor core, the carbon fiber composite sheath and the cobalt iron alloy rotor core, and the titanium alloy hollow shaft and the cobalt iron alloy rotor core are fixedly connected by interference fit, bonding or welding.

2. The lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure according to claim 1, characterized in that, The reference threshold is 1.5 × 10⁻⁶. -6 / ℃; The silicon steel sheets of the ultra-thin non-oriented silicon steel sheet stator core are coated with a high-performance composite coating containing nanoparticles. A dimensional chain is established between the stator core and the titanium alloy motor housing to form an interference fit at room temperature and maintain a tight fit at the lowest operating temperature. The interface gap between the two is filled with a modified epoxy resin thermally conductive adhesive containing boron nitride.

3. The lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure according to claim 1, characterized in that, The flat copper wire armature winding uses polyimide-nano-ceramic composite insulation winding wire, and is filled with low-temperature resistant and high-toughness modified polyester impregnation varnish through dynamic vacuum pressure impregnation process. Thin-film thermocouples and heating elements based on MEMS technology are pre-embedded in the winding to realize real-time temperature monitoring and closed-loop regulation.

4. The lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure according to claim 1, characterized in that, The outer surface of the titanium alloy motor housing is provided with multiple radial heat dissipation fins. The surface of the radial heat dissipation fins is treated with laser texturing and then plasma sprayed with an alumina-titanium dioxide composite ceramic coating.

5. The lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure according to claim 1, characterized in that, The ammonia-ethane working fluid capillary core low-temperature heat pipe is inserted into the ultra-thin non-oriented silicon steel sheet stator core with an interference fit and fixed by brazing. The interface gap between the heat pipe and the ultra-thin non-oriented silicon steel sheet stator core is filled with modified epoxy resin thermally conductive adhesive containing boron nitride.

6. The lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure according to claim 1, characterized in that, The interface between the carbon fiber composite sheath and the cobalt-iron alloy rotor core is filled with a high-toughness, low-temperature epoxy adhesive.

7. The lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure according to claim 1, characterized in that, Each piece of the cobalt-iron alloy rotor core is bonded together and aligned through through holes by aluminum alloy rods. The two ends of the aluminum alloy rods are connected to the aluminum alloy end plates by friction stir welding to form an integrated structure.

8. The lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure according to claim 1, characterized in that, The samarium cobalt permanent magnet is embedded in the slot of the cobalt-iron alloy rotor core using a built-in uniform segmented structure. The gaps between the samarium cobalt permanent magnets and between the samarium cobalt permanent magnets and the cobalt-iron alloy rotor core are filled with high-toughness low-temperature epoxy adhesive. The samarium cobalt permanent magnets and the slot are assembled by forming an interference fit at room temperature and maintaining a tight fit at the lowest operating temperature through a dimensional chain.

9. The lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure according to claim 1, characterized in that, The titanium alloy hollow shaft and the cobalt-iron alloy rotor core are connected by a composite assembly method that combines spline connection and high-toughness low-temperature epoxy adhesive bonding.

10. The lightweight permanent magnet propulsion motor resistant to high and low temperatures and low air pressure according to claim 1, characterized in that, Both the boron nitride-modified epoxy thermal conductive adhesive and the high-toughness low-temperature epoxy adhesive are uniformly coated using a high-precision, quantitative, non-contact spraying dispensing process, minimizing the amount of adhesive used at the interface.

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