Retainer with functional gradient structure and preparation method thereof

Abstract

The invention relates to the field of mechanical design and composite high polymer material manufacturing, in particular to a retainer with a functional gradient structure and a preparation method thereof, and the retainer is composed of a three-layer functional gradient structure of a reinforcing layer, a lubricating wear-resistant layer and a toughening layer. The composite material is prepared from prepreg impregnated with high-molecular-weight phenolic resin B, prepreg of phenolic resin C containing a lubricating wear-resistant modifier and a foaming agent, and prepreg of phenolic resin D containing a flexibilizer. The preparation method comprises the following steps: synthesizing phenolic resin with two molecular weights; preparing modified resin; dipping cotton cloth; adjusting a winding sequence according to a bearing guide manner; by means of the design, the problems that a traditional retainer is large in brittleness, high in noise, insufficient in lubrication, free of functional layering and poor in adaptability are solved, cooperation of low noise, long-acting lubrication and high strength is achieved, the retainer can adapt to inner / outer guide bearings, and the requirements of precision bearings in the 3C field and the aerospace field are met.

Description

Technical Field

[0001] This invention relates to the fields of mechanical design and composite polymer material manufacturing, and particularly to a cage with a functional gradient structure and its preparation method. Background Technology

[0002] In existing technologies, when precision bearings with phenolic resin cages are used in the 3C industry, the molecular structure of phenolic resin itself limits its overall brittleness. The benzene rings on its macromolecules are directly connected to methylene groups, resulting in high molecular rigidity. During bearing operation, the cage is prone to vortexing, which leads to collisions with the bearing flanges and generates noise. This noise problem cannot meet the 3C industry's requirements for low-noise precision bearings. At the same time, the lubrication performance of traditional phenolic resin cages relies on an external lubrication system. After long-term operation, insufficient lubrication can occur due to the consumption or loss of lubricating grease, leading to increased wear between the cage and the steel balls and directly shortening the bearing's service life.

[0003] The applicant's invention patent application, filed in 2023 with patent number CN116641235A, discloses "a porous phenolic fabric composite material and its preparation method, cage, and bearing." This technology prepares a single porous homogeneous phenolic fabric composite material, utilizing the pores inside the material to store lubricating oil. During bearing operation, lubricating oil can be slowly released to achieve long-term lubrication.

[0004] However, this technical solution still has obvious limitations in practical applications and is difficult to adapt to the needs of more extensive high-precision and high-speed working conditions: it adopts a single porous homogeneous structure without functional layer design, which cannot specifically solve the differentiated needs of different scenarios. For example, when precision bearings in the 3C industry are subjected to high-frequency whirl, there is a lack of toughening structure to absorb collision energy and reduce noise, and it is also unable to achieve "lubrication-reinforcement" synergy to simultaneously meet the comprehensive performance requirements of low noise, high strength and long-term lubrication; its winding molding has no directional design logic, and only aims to ensure the uniformity of the porous structure. It does not combine the actual working conditions of the bearing's internal and external guidance to match the functional layer position distribution, which results in the inability to maximize the functional performance of the material and limits its applicability to multiple scenarios. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a cage with a functionally graded structure and its preparation method. This addresses the issues of high resin brittleness caused by the direct connection of benzene rings to methylene groups on the phenolic resin macromolecules in existing phenolic resin cages, and the lack of functional layered design in existing technologies, which fails to address the differentiated needs of different scenarios.

[0006] The technical solution adopted in this invention is: a method for preparing a cage with a functionally graded structure, comprising the following steps: S1. Synthesize low molecular weight phenolic resin A and high molecular weight phenolic resin B; S2. The lubricating and wear-resistant modifier is uniformly dispersed in ethanol and mixed with the foaming agent and the low molecular weight phenolic resin A to prepare phenolic resin C; the toughening agent is uniformly dispersed in ethanol or acetone and mixed with the low molecular weight phenolic resin A to prepare phenolic resin D. S3. Using cotton fabrics with different yarn counts, impregnate them with the high molecular weight phenolic resin B, the phenolic resin C, and the phenolic resin D respectively to obtain prepreg B, prepreg C, and prepreg D. S4. The three types of prepreg fabrics prepared in step S3 are wound and cured in the designed order to obtain a phenolic fabric composite material with a three-layer functional gradient structure. The three-layer structure includes a reinforcing layer composed of prepreg fabric B, a lubricating and wear-resistant layer composed of prepreg fabric C, and a toughening layer composed of prepreg fabric D. S5. The phenolic fabric composite material prepared in step S4 is machined into a cage with a functional gradient structure.

[0007] As a preferred embodiment, the step of preparing low molecular weight phenolic resin A in step S1 is as follows: First, a phenol and formaldehyde mixed solution in a 1:1 ratio and an ammonia solution with a concentration of 1-10% are added to a reaction vessel, the temperature is raised to 40-60℃ and kept at that temperature for 20-60 min, then the temperature is raised to 65-85℃ and kept at that temperature for 40-120 min. After stopping the reaction, the temperature of the reaction vessel is lowered. When the temperature of the reaction vessel drops to 50-60℃, vacuum dehydration is performed for 1-3 h / kg to obtain low molecular weight phenolic resin A. The steps for preparing high molecular weight phenolic resin B are as follows: First, a phenol and formaldehyde mixed solution in a 1:1 ratio and a 5-10% ammonia solution are added to a reaction vessel. The temperature is raised to 40-60℃ and held for 20-60 min. Then, the temperature is raised to 65-85℃ and held for 40-120 min. Finally, the temperature is raised to 80-100℃ and held for 10-30 min. After stopping the reaction, the temperature of the reaction vessel is lowered. When the temperature of the reaction vessel drops to 50-70℃, vacuum dehydration is performed for 1.5-3.5 h / kg to obtain high molecular weight phenolic resin B.

[0008] As a preferred embodiment, the low molecular weight phenolic resin A has a molecular weight of 400-600 g / mol; and the high molecular weight phenolic resin B has a molecular weight of 1200-1600 g / mol.

[0009] As a preferred embodiment, the foaming agent comprises DPT, acetone, ethanol, and urea. DPT is fully dissolved in acetone, and urea is then fully dissolved in anhydrous ethanol. The two are mixed to obtain the foaming agent, wherein the mass ratio of DPT to urea is 1:(1-3), the amount of DPT is 1-10 g / kg, and the total amount of acetone and ethanol is 200-450 ml / kg. The lubricating and wear-resistant modifier comprises one or more of porous graphite lubricant, graphene nanospheres, molybdenum disulfide, tungsten disulfide, and hexagonal boron nitride nanoparticles, wherein the specific surface area of ​​the porous graphite lubricant is 6-10 m². 2 / g, the graphene nanospheres have a particle size of 10-60nm, and the D50 of molybdenum disulfide, tungsten disulfide, and hexagonal boron nitride nanoparticles are all 0.5-5μm; the toughening agent includes one or more of polyetherimide and hydroxyl-modified polyethersulfone.

[0010] Furthermore, in the preparation of phenolic resin D, the amount of ethanol or acetone is 50-100 ml / g, the specific viscosity of hydroxyl-modified polyethersulfone is 0.40-0.52 L / g, and the particle size of polyetherimide powder is 30-50 μm.

[0011] As a preferred embodiment, in step S3, when impregnating the high molecular weight phenolic resin B, cotton cloth with a count of 100-120 is used, and the drying temperature is 100-120℃; when impregnating the resin D, cotton cloth with a count of 80-120 is used, and the drying temperature is 90-120℃; when impregnating the resin C, cotton cloth with a count of 60-80 is used, and the drying temperature is 90-110℃.

[0012] Furthermore, depending on the bearing guiding method, the internal and external properties of the phenolic cotton fabric composite material can be designed. If the bearing is externally guided, the prepreg B impregnated with high molecular weight phenolic resin B is wound first, then the prepreg C impregnated with phenolic resin C is wound, and finally the prepreg D impregnated with phenolic resin D is wound. If the bearing is internally guided, the prepreg D impregnated with phenolic resin D is wound first, then the prepreg C impregnated with phenolic resin C is wound, and finally the prepreg B impregnated with high molecular weight phenolic resin B is wound.

[0013] As a preferred embodiment, in step S4, the winding and forming process employs a hot rolling method, wherein: when winding the prepreg impregnated with resin B, the rolling temperature is 110-140℃ and the rolling pressure is 0.4-1.0MPa; when winding the prepreg impregnated with resin C, the rolling temperature is 90-120℃ and the rolling pressure is 0.1-0.5MPa; and when winding the prepreg impregnated with resin D, the rolling temperature is 120-150℃ and the rolling pressure is 0.3-0.8MPa.

[0014] As a preferred embodiment, in step S4, the curing method includes the following steps: first heating the prepreg fabric after winding to 90-120℃ and keeping it at that temperature for 1-2 hours, and then heating it to 140-170℃ and keeping it at that temperature for 4-9 hours.

[0015] A cage with a functional gradient structure, the cage being composed of three layers of materials in sequence, including a reinforcing layer composed of prepreg B, a lubricating and wear-resistant layer composed of prepreg C, and a toughening layer composed of prepreg D.

[0016] The beneficial effects of this invention are: To address the shortcomings of existing technologies, this invention proposes a cage with a functionally graded structure and its preparation method. This solves the problems of high resin brittleness caused by the direct connection of benzene rings to methylene groups on the phenolic resin macromolecules in existing phenolic resin cages, and the lack of functional layering design in existing technologies, which fails to address the differentiated needs of various scenarios. This invention has the following technical advantages: Firstly, the present invention comprises a three-layer functional structure consisting of a reinforcing layer composed of prepreg fabric B, a lubricating and wear-resistant layer composed of prepreg fabric C, and a toughening layer composed of prepreg fabric D. This structure achieves comprehensive optimization and synergistic improvement of cage performance, effectively solving the technical problem that traditional cages cannot simultaneously achieve noise reduction, lubrication, and strength. The cage guide surface is designed with a toughening layer, which actively absorbs the vortex collision energy between the cage and the flange during bearing operation, significantly reducing vibration and noise, ensuring quiet operation of the bearing, and meeting the core requirement of precision equipment for low noise. The lubricating and wear-resistant layer contains pre-impregnated lubricating oil that gradually precipitates out as it comes into contact with the steel balls and is compressed and heated, further ensuring lubrication. It also conducts heat generated during operation, preventing excessive local temperature rise from affecting material properties and ensuring stable bearing operation. The reinforcing layer on the other side provides solid structural support for the cage, ensuring overall load-bearing capacity, and making the cage less prone to deformation or damage during long-term high-frequency operation. The three layers work together to provide the cage with excellent noise reduction, long-lasting lubrication, and reliable mechanical strength, making it suitable for various complex working conditions.

[0017] Secondly, the three-layer functional structure of this invention possesses excellent adaptability to various operating conditions. It can adjust the winding sequence of each functional layer according to different bearing guidance methods (internal or external), ensuring that the toughening layer always corresponds to the collision contact surface between the cage and the flange, and the reinforcement layer corresponds to the main stress surface. This ensures that each functional layer functions optimally, maximizing the cage's performance. When the bearing is externally guided, the reinforcement layer is wound first, followed by the lubricating and wear-resistant layer, and finally the toughening layer, allowing the toughening layer to directly contact the external flange. When the bearing is internally guided, the winding sequence is adjusted to prioritize the toughening layer, ensuring it conforms to the internal flange. This flexible adaptation design allows the cage to adapt to the installation and operation requirements of different types of bearings, broadening its application range.

[0018] Thirdly, this invention uses high-count cotton fabric impregnated with high-molecular-weight phenolic resin, and works in conjunction with impregnation and winding processes to achieve a reinforcing layer design while avoiding defects such as delamination and porosity. Furthermore, this invention directly mixes and impregnates the foaming agent and phenolic resin, reducing the previous two-step process of first impregnating the foaming agent and then the resin to a single step, increasing production efficiency by nearly 30% and reducing organic solvent usage by 30%, making it more environmentally friendly and protecting the health of operators. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This paper compares the performance of different embodiments of the cage preparation of the present invention with that of the prior art. Detailed Implementation

[0021] The present invention will now be described in detail through exemplary embodiments. However, it should be understood that, without further description, elements, structures, and features in one embodiment may be advantageously incorporated into other embodiments.

[0022] It should be noted that, unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "a," "an," or "the," and similar words used in the specification and claims of this patent application do not express a limitation of quantity, but rather indicate the presence of at least one; terms such as "comprising" or "including" indicate that the elements or objects preceding "comprising" encompass the elements or objects listed following "comprising" or "including" and their equivalents, but do not exclude other elements or objects having the same function.

[0023] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0024] Example 1 ① Synthesize two types of phenolic resins Phenolic resin A: Phenol and formaldehyde in a 1:1 ratio, along with 3% ammonia, were added to a reaction vessel. The mixture was kept at 60°C for 40 min and then at 75°C for 110 min, resulting in emulsification and layering. The reaction was then stopped. When the reaction vessel temperature dropped to 55°C, vacuum dehydration was performed for 3 h / kg. The molecular weight (Mw) of the phenolic resin was controlled to be 600 g / mol.

[0025] Phenolic resin B: Phenol and formaldehyde in a 1:1 ratio, along with 10% ammonia, were added to a reaction vessel. The mixture was kept at 40°C for 40 min, 85°C for 60 min, and 100°C for 25 min. The reaction was then stopped. When the temperature of the reaction vessel dropped to 70°C, vacuum dehydration was performed for 3.5 h / kg. The molecular weight (Mw) of the phenolic resin was controlled to be 1600 g / mol.

[0026] ② Prepare two resins according to their respective weight percentages. Phenolic resin C: DPT is fully dissolved in acetone, and urea is fully dissolved in anhydrous ethanol. 0.5% of dopamine-treated graphene nanospheres are ultrasonically and uniformly dispersed in anhydrous ethanol. The three solutions are mixed evenly with phenolic resin A. The amount of DPT is 6 g / kg, the ratio of DPT to urea is 1:2, the total amount of acetone and ethanol is 350 ml / kg, and the particle size of the graphene nanospheres is 10 nm.

[0027] Phenolic resin D: 2% of the theoretical weight of hydroxyl-modified polyethersulfone was ultrasonically dispersed in acetone, and phenolic resin A was added and mixed evenly. The amount of acetone was 100 ml / g, and the specific viscosity of the hydroxyl-modified polyethersulfone was 0.52 L / g.

[0028] ③ Cotton cloths were impregnated with three different resins. Desized cotton fabric with 100-count yarn was impregnated with resin B on an impregnation machine at a drying temperature of 120℃ and an impregnation speed of 2.5 m / min.

[0029] Desized cotton fabric with 80 count yarn was impregnated with D resin on an impregnation machine at a drying temperature of 100℃ and an impregnation speed of 2 meters / min.

[0030] Desized cotton fabric with 60 count yarn was impregnated with C resin on an impregnation machine at a drying temperature of 110℃ and an impregnation speed of 3.5 m / min.

[0031] ④ Winding and curing molding The bearing is externally guided. Under the conditions of roller pressing temperature of 130℃ and roller pressing pressure of 0.8MPa, the prepreg impregnated with B is wound first, then the prepreg impregnated with C is wound under the conditions of roller pressing temperature of 100℃ and roller pressing pressure of 0.5MPa, and finally the prepreg impregnated with D is wound under the conditions of 120℃ and roller pressing pressure of 0.7MPa.

[0032] The material is sintered and cured in a sintering furnace with the following curing process parameters: 90℃ for 2 hours and 140℃ for 9 hours, to obtain a phenolic cotton fabric composite material with a functional gradient structure, which is then machined into a retainer.

[0033] Example 2 ① Synthesize two types of phenolic resins Phenolic resin A: Phenol and formaldehyde in a 1:1 ratio, along with 5% ammonia, were added to a reaction vessel. The mixture was kept at 60°C for 20 minutes and then at 70°C for 120 minutes, resulting in emulsification and layering. The reaction was then stopped. When the temperature of the reaction vessel dropped to 50°C, vacuum dehydration was performed for 1 hour per kg. The molecular weight (Mw) of the phenolic resin was controlled to be 550 g / mol.

[0034] Phenolic resin B: Phenol and formaldehyde in a 1:1 ratio, along with 8% ammonia, were added to a reaction vessel. The mixture was kept at 60℃ for 40 min, 80℃ for 40 min, and 95℃ for 10 min. The reaction was then stopped. When the temperature of the reaction vessel dropped to 50℃, vacuum dehydration was performed for 1.5 h / kg. The molecular weight (Mw) of the phenolic resin was controlled to be 1200 g / mol.

[0035] ② Prepare two resins according to their respective weight percentages. Phenolic Resin C: Dissolve DPT thoroughly in acetone, then dissolve urea thoroughly in anhydrous ethanol. Ultrasonically disperse 3% dopamine-treated porous graphite lubricant, 1% dopamine-treated graphene nanospheres, and 5% dopamine-treated tungsten disulfide in anhydrous ethanol. Mix these three solutions thoroughly with phenolic resin A. The amount of DPT used is 1 g / kg, with a DPT:urea ratio of 1:1. The total amount of acetone and ethanol used is 450 ml / kg. The specific surface area of ​​the porous graphite lubricant is 6 m². 2 / g, the graphene nanospheres have a particle size of 60nm, and the tungsten disulfide D50 is 5μm.

[0036] Phenolic resin D: 3% of the theoretical weight of polyetherimide was ultrasonically dispersed in anhydrous ethanol, and then phenolic resin A was added and mixed evenly. The amount of anhydrous ethanol was 50 ml / g, and the particle size of the polyetherimide powder was 40 μm.

[0037] ③ Cotton cloths were impregnated with three different resins. Desized cotton fabric with 100-count yarn was impregnated with resin B on an impregnation machine at a drying temperature of 120℃ and an impregnation speed of 1 meter / min.

[0038] Desized cotton fabric with 80 count yarn was impregnated with D resin on an impregnation machine at a drying temperature of 90℃ and an impregnation speed of 1 meter / min.

[0039] Desized cotton fabric with 60 count yarn was impregnated with C resin on an impregnation machine at a drying temperature of 110℃ and an impregnation speed of 2 meters / min.

[0040] ④ Winding and curing molding The bearing is externally guided. Under the conditions of roller pressing temperature of 140℃ and roller pressing pressure of 0.4MPa, the prepreg impregnated with B is wound first, then the prepreg impregnated with C is wound under the conditions of roller pressing temperature of 90℃ and roller pressing pressure of 0.1MPa, and finally the prepreg impregnated with D is wound under the conditions of 130℃ and roller pressing pressure of 0.8MPa.

[0041] The material is sintered and cured in a sintering furnace with the following curing parameters: 110℃ for 1.5h and 160℃ for 6h, to obtain a phenolic cotton fabric composite material with a functional gradient structure, which is then machined into a retainer.

[0042] Example 3 ① Synthesize two types of phenolic resins Phenolic resin A: Phenol and formaldehyde in a 1:1 ratio, along with 1% ammonia, were added to a reaction vessel. The mixture was kept at 40°C for 60 min and then at 85°C for 40 min, resulting in emulsification and layering. The reaction was then stopped. When the temperature of the reaction vessel dropped to 60°C, vacuum dehydration was performed for 1 h / kg. The molecular weight (Mw) of the phenolic resin was controlled to be 400 g / mol.

[0043] Phenolic resin B: Phenol and formaldehyde in a 1:1 ratio, along with 10% ammonia, were added to a reaction vessel. The mixture was kept at 60℃ for 20 min, 65℃ for 120 min, and 90℃ for 30 min. The reaction was then stopped. When the temperature of the reaction vessel dropped to 60℃, vacuum dehydration was performed for 2 h / kg. The molecular weight (Mw) of the phenolic resin was controlled to be 1500 g / mol.

[0044] ② Prepare two resins according to their respective weight percentages. Phenolic Resin C: Dissolve DPT thoroughly in acetone, then dissolve urea thoroughly in anhydrous ethanol. Ultrasonically disperse 5% dopamine-treated porous graphite lubricant and 5% dopamine-treated nano-boron nitride in anhydrous ethanol. Mix these three solutions thoroughly with phenolic resin A. The amount of DPT used is 10 g / kg, the DPT:urea ratio is 1:3, and the total amount of acetone and ethanol used is 250 ml / kg. The specific surface area of ​​the porous graphite lubricant is 10 m² / kg. 2 / g, hexagonal boron nitride nanoparticles are 0.5μm.

[0045] Phenolic resin D: 10% of the theoretical weight of hydroxyl-modified polyethersulfone was ultrasonically dispersed in acetone, and phenolic resin A was added and mixed evenly. The amount of acetone was 100 ml / g, and the specific viscosity of the hydroxyl-modified polyethersulfone was 0.40 L / g.

[0046] ③ Cotton cloths were impregnated with three different resins. Desized cotton fabric with 120 count yarn was impregnated with resin B on an impregnation machine at a drying temperature of 100℃ and an impregnation speed of 1 meter / min.

[0047] Desized cotton fabric with 100-count yarn was impregnated with D resin on an impregnation machine at a drying temperature of 120℃ and an impregnation speed of 3 meters / min.

[0048] Desized cotton fabric with 80 count yarn was impregnated with C resin on an impregnation machine at a drying temperature of 90℃ and an impregnation speed of 2.5 m / min.

[0049] ④ Winding and curing molding The bearing is internally guided. Under the conditions of roller pressing temperature of 150℃ and roller pressing pressure of 0.3MPa, the prepreg impregnated with D is wound first, then the prepreg impregnated with C is wound under the conditions of roller pressing temperature of 120℃ and roller pressing pressure of 0.2MPa, and finally the prepreg impregnated with B is wound under the conditions of 110℃ and roller pressing pressure of 1.0MPa.

[0050] The material is sintered and cured in a sintering furnace with the following curing parameters: 120℃ for 1 hour and 170℃ for 4 hours to obtain a phenolic cotton fabric composite material with a functional gradient structure, which is then machined into a retainer.

[0051] Figure 1 This invention relates to the performance of the phenolic cotton fabric composite material and its retainer, which combine two lubrication methods. Through... Figure 1 It can be known that: 1. The phenolic cotton fabric composite material with a functional gradient structure prepared by this invention has high mechanical strength, while the oil content, friction performance and toughness of the material are significantly improved.

[0052] 2. The bearing equipped with the functionally graded cage prepared according to the present invention, after bench testing, showed vibration noise below 56 decibels and no abnormal noise.

[0053] The cage with a functional gradient structure and its preparation method not only meet the application requirements of 3C bearings, but can also be widely used in precision bearings in other fields such as aerospace, meeting the future development needs of my country's aerospace and industrial machine tools, with significant economic and social benefits.

[0054] It should be noted that although the present invention has been described through the above embodiments, the present invention may have many other embodiments. Without departing from the spirit and scope of the present invention, those skilled in the art can obviously make various corresponding changes and modifications to the present invention, but all such changes and modifications should fall within the scope of protection of the appended claims and their equivalents.

Claims

1. A method for fabricating a cage with a functionally graded structure, characterized in that, Includes the following steps: S1. Synthesize low molecular weight phenolic resin A and high molecular weight phenolic resin B; S2. The lubricating and wear-resistant modifier is uniformly dispersed in ethanol and mixed with the foaming agent and the low molecular weight phenolic resin A to prepare phenolic resin C; the toughening agent is uniformly dispersed in ethanol or acetone and mixed with the low molecular weight phenolic resin A to prepare phenolic resin D. S3. Using cotton fabrics with different yarn counts, impregnate them with the high molecular weight phenolic resin B, the phenolic resin C, and the phenolic resin D respectively to obtain prepreg B, prepreg C, and prepreg D. S4. The three types of prepreg fabrics prepared in step S3 are wound and cured in the designed order to obtain a phenolic fabric composite material with a three-layer functional gradient structure. The three-layer structure includes a reinforcing layer composed of prepreg fabric B, a lubricating and wear-resistant layer composed of prepreg fabric C, and a toughening layer composed of prepreg fabric D. S5. The phenolic fabric composite material prepared in step S4 is machined into a cage with a functional gradient structure.

2. The method for preparing a cage with a functionally graded structure according to claim 1, characterized in that, The steps for preparing low molecular weight phenolic resin A in step S1 are as follows: First, a phenol and formaldehyde mixed solution in a 1:1 ratio and an ammonia solution with a concentration of 1-10% are added to a reaction vessel. The temperature is raised to 40-60℃ and held for 20-60 min. Then, the temperature is raised to 65-85℃ and held for 40-120 min. After stopping the reaction, the temperature of the reaction vessel is lowered. When the temperature of the reaction vessel drops to 50-60℃, it is vacuum dehydrated for 1-3 h / kg to obtain low molecular weight phenolic resin A. The steps for preparing high molecular weight phenolic resin B are as follows: First, a phenol and formaldehyde mixed solution in a 1:1 ratio and a 5-10% ammonia solution are added to a reaction vessel. The temperature is raised to 40-60℃ and held for 20-60 min. Then, the temperature is raised to 65-85℃ and held for 40-120 min. Finally, the temperature is raised to 80-100℃ and held for 10-30 min. After stopping the reaction, the temperature of the reaction vessel is lowered. When the temperature of the reaction vessel drops to 50-70℃, vacuum dehydration is performed for 1.5-3.5 h / kg to obtain high molecular weight phenolic resin B.

3. The method for preparing a cage with a functionally graded structure according to claim 2, characterized in that, The low molecular weight phenolic resin A has a molecular weight of 400-600 g / mol; the high molecular weight phenolic resin B has a molecular weight of 1200-1600 g / mol.

4. The method for preparing a cage with a functionally graded structure according to claim 1, characterized in that, In step S2, the foaming agent includes DPT, acetone, ethanol and urea. DPT is fully dissolved in acetone, and then urea is fully dissolved in anhydrous ethanol. The two are mixed to obtain the foaming agent. The mass ratio of DPT to urea is 1:(1-3), the amount of DPT is 1-10g / kg, and the total amount of acetone and ethanol is 200-450ml / kg. The lubricating and wear-resistant modifier includes one or more of porous graphite lubricants, graphene nanospheres, molybdenum disulfide, tungsten disulfide, and hexagonal boron nitride nanoparticles, wherein the specific surface area of ​​the porous graphite lubricant is 6-10 m². 2 / g, the particle size of graphene nanospheres is 10-60nm, and the D50 of molybdenum disulfide, tungsten disulfide and hexagonal boron nitride nanoparticles is 0.5-5μm; The toughening agent includes one or more of polyetherimide and hydroxyl-modified polyethersulfone.

5. The method for preparing a cage with a functionally graded structure according to claim 4, characterized in that, In the preparation of phenolic resin D, the amount of ethanol or acetone is 50-100 ml / g, the specific viscosity of hydroxyl-modified polyethersulfone is 0.40-0.52 L / g, and the particle size of polyetherimide powder is 30-50 μm.

6. The method for preparing a cage with a functionally graded structure according to claim 1, characterized in that, In step S3, when impregnating the high molecular weight phenolic resin B, cotton cloth with 100-120 count yarn is used, and the drying temperature is 100-120℃; when impregnating the resin D, cotton cloth with 80-120 count yarn is used, and the drying temperature is 90-120℃; when impregnating the resin C, cotton cloth with 60-80 count yarn is used, and the drying temperature is 90-110℃.

7. The method for preparing a cage with a functionally graded structure according to claim 1, characterized in that, In step S4, the winding and forming process employs a hot rolling method, wherein: when winding the prepreg impregnated with resin B, the rolling temperature is 110-140℃ and the rolling pressure is 0.4-1.0MPa; when winding the prepreg impregnated with resin C, the rolling temperature is 90-120℃ and the rolling pressure is 0.1-0.5MPa; and when winding the prepreg impregnated with resin D, the rolling temperature is 120-150℃ and the rolling pressure is 0.3-0.8MPa.

8. The method for preparing a cage with a functionally graded structure according to claim 1, characterized in that, In step S4, the curing method includes the following steps: first heating the prepreg fabric after winding to 90-120℃ and keeping it at that temperature for 1-2 hours, and then heating it to 140-170℃ and keeping it at that temperature for 4-9 hours.

9. A cage with a functionally graded structure, characterized in that... The cage is prepared by the method according to any one of claims 1-8, and is composed of three layers of materials in sequence, including a reinforcing layer composed of prepreg B, a lubricating and wear-resistant layer composed of prepreg C, and a toughening layer composed of prepreg D.

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