Macromolecular wear-resistant layer on surface of variable-speed cam and preparation method of macromolecular wear-resistant layer

Abstract

The invention belongs to the field of surface treatment of mechanical parts, and discloses a high-molecular wear-resistant layer on the surface of a variable-speed cam and a preparation method thereof.The high-molecular wear-resistant layer comprises a variable-speed cam base body, the outer surface of the variable-speed cam base body is provided with a wear-resistant layer, and the wear-resistant layer is composed of, by weight, 40%-60% of high-molecular polymer base materials, 20%-35% of blend fibers, 1%-3% of a coupling agent 10%-20% of solid self-lubricating particles and 5%-15% of nano reinforced particles; the invention aims to overcome the defects of the surface treatment of the variable-speed cam in the prior art, and develops a high-performance high-molecular wear-resistant layer which can effectively improve the wear resistance of the surface of the variable-speed cam, reduce the friction coefficient and prolong the service life through innovative design and process. Therefore, the harsh requirements of mechanical equipment on the wear resistance of the surface of the variable-speed cam under high-speed and heavy-load working conditions are met.

Description

Technical Field

[0001] The present invention relates to the technical field of surface treatment of mechanical parts, and specifically to a polymer wear-resistant layer on the surface of a variable-speed cam and a preparation method thereof. Background Art

[0002] In a mechanical transmission system, as a key component, the operating conditions of a variable-speed cam are extremely complex. In the valve train of an automobile engine, the variable-speed cam needs to precisely control the opening and closing of the valve, and may experience thousands of reciprocating motions per minute. In the intermittent transmission device of industrial automation equipment, the variable-speed cam also frequently pushes the driven component to achieve periodic motion. This high-frequency relative motion causes the surface of the cam to bear extremely high friction and wear. Traditional surface treatment methods for cams mainly include quenching, carburizing, electroplating, etc. Quenching treatment can increase the surface hardness of the cam, but it is only applicable to cams of specific materials and is prone to surface cracks, reducing the toughness of the cam. Under complex stress conditions, the wear is still relatively fast. The carburizing treatment process is complex, costly, and the thickness of the carburized layer is limited. After long-term use, the carburized layer wears out, and the wear-resistant performance of the cam drops significantly. The electroplating process can form a metal coating on the surface of the cam. However, the bonding force between the coating and the substrate is often not ideal, and the coating is prone to peeling off under high-speed and heavy-load operating conditions, resulting in cam failure. With the rapid development of mechanical equipment towards high speed and heavy load, such as large marine engines, high-speed CNC machine tools, etc., the performance requirements for variable-speed cams are becoming increasingly stringent. The variable-speed cams in these devices not only have to bear higher loads but also maintain a stable working state during long-term continuous operation. The traditional surface treatment methods for cams are difficult to meet the growing performance requirements of high wear resistance, low friction, and long service life. Therefore, a polymer wear-resistant layer on the surface of a variable-speed cam and a preparation method thereof are proposed, which can effectively improve the wear-resistant performance of the surface of the variable-speed cam, reduce the friction coefficient, and extend the service life. Summary of the Invention

[0003] The present invention aims to overcome the many deficiencies in the surface treatment of variable-speed cams in the prior art. Through innovative design and processes, a high-performance polymer wear-resistant layer is developed, which can effectively improve the wear-resistant performance of the surface of the variable-speed cam, reduce the friction coefficient, and extend the service life, so as to meet the stringent requirements for the wear-resistant performance of the surface of the variable-speed cam under high-speed and heavy-load operating conditions of mechanical equipment.

[0004] To achieve the above object, the present invention provides the following technical solutions: The technical solution provided by the present invention is: a polymer wear-resistant layer on the surface of a variable-speed cam, including a variable-speed cam matrix, and a wear-resistant layer is provided on the outer surface of the variable-speed cam matrix. The wear-resistant layer is composed of the following components by weight percentage: 40%-60% of a polymer matrix material, 20%-35% of a blended fiber, 10%-20% of a solid self-lubricating particle, and 5%-15% of a nano-enhanced particle.

[0005] The polymer matrix material includes a mixture composed of polyimide and epoxy resin, and the weight ratio of the polyimide to the epoxy resin mixture is 1:0.5-1.5. Polyimide has excellent high-temperature resistance and mechanical strength, while epoxy resin has good adhesion performance and toughness. After the two are mixed, the advantages of both can be combined to provide a stable matrix support for the wear-resistant layer.

[0006] The blended fiber includes a mixture composed of carbon fiber, glass fiber, and nanofiber, and the weight ratio of the carbon fiber, glass fiber, and nanofiber mixture in the blended fiber is 2-3:1-2:1. Carbon fiber has the characteristics of high strength and low density, glass fiber can provide good impact resistance, and nanofiber can enhance the interfacial bonding strength between the fiber and the matrix. After the three are mixed, the mechanical properties and wear resistance of the wear-resistant layer can be significantly improved.

[0007] The solid self-lubricating particle includes a composite particle composed of graphite, tungsten disulfide, and polytetrafluoroethylene, and the weight ratio of each component is 1-2:0.5-1:1-1.5. Graphite and tungsten disulfide have good self-lubricating properties, while polytetrafluoroethylene has excellent wear resistance and chemical stability. The addition of the composite particle can effectively reduce the friction coefficient and reduce wear.

[0008] The nano-enhanced particle includes a mixture of nano-silica, nano-silicon carbide, and nano-aluminum oxide, and the weight ratio of each component is 1-2:1:0.5-1. The addition of the nano-particle can significantly improve the hardness and abrasive wear resistance of the wear-resistant layer, while improving the toughness and fatigue resistance of the material.

[0009] Furthermore, the surface of the polymer matrix material and the blended fiber is modified by a chemical coupling agent. The chemical coupling agent is a composite of a silane coupling agent and an aluminate coupling agent, and the weight ratio of the silane coupling agent to the aluminate coupling agent is 1-2:1. The use of the chemical coupling agent can enhance the bonding strength between the fiber and the polymer matrix material and improve the overall performance of the wear-resistant layer.

[0010] Furthermore, the thickness of the wear-resistant layer is 0.3-0.8 mm, and the outer surface of the wear-resistant layer is designed as a bionic friction surface with micro-pits and protrusions. The depth of the micro-pits is 10-30 μm, and the spacing is 50-100 μm, which can effectively store lubricating oil and capture wear debris generated by friction, reducing abrasive wear.

[0011] The bonding surface between the inner surface of the wear-resistant layer and the variable-speed cam matrix is a multi-layer gradient structure, which from the inside to the outside is successively a diffusion layer, a transition layer and a working layer. The thickness of the diffusion layer is 20 - 50 μm, the thickness of the transition layer is 30 - 70 μm, and the thickness of the working layer accounts for 40% - 50% of the total thickness of the wear-resistant layer. The design of the multi-layer gradient structure can achieve a progressive combination of the wear-resistant layer and the matrix, improving the bonding strength and reliability.

[0012] Furthermore, an annular sealing groove is provided at the outer edge of the wear-resistant layer. The cross-section of the sealing groove is V-shaped, with a depth of 0.5 - 1.5 mm and a width of 2 - 4 mm. An oil-resistant and wear-resistant elastic sealing ring is embedded in the sealing groove. The material of the sealing ring is a blend of silicone rubber and nitrile rubber, and the weight ratio of the two is 1 - 2:1. The design of the sealing groove and the sealing ring can effectively prevent the leakage of lubricating oil and the entry of external impurities, extending the service life of the cam.

[0013] Furthermore, a preparation method of a polymer wear-resistant layer on the surface of a variable-speed cam is characterized by the following steps: S1: Prepare polyimide and epoxy resin, and mix them evenly in a weight ratio of 1:0.5 - 1.5 to form a polymer matrix material; Prepare carbon fiber, glass fiber and nanofiber, and mix them in a weight ratio of 2 - 3:1 - 2:1 to form a blended fiber; Prepare graphite, tungsten disulfide and polytetrafluoroethylene, and mix them in a weight ratio of 1 - 2:0.5 - 1:1 - 1.5 to form solid self-lubricating particles; Prepare nano-silica, nano-silicon carbide and nano-aluminum oxide, and mix them in a weight ratio of 1 - 2:1:0.5 - 1 to form nano-reinforcing particles; Prepare silane coupling agent and aluminate coupling agent, and mix them in a weight ratio of 1 - 2:1 for standby to form a chemical coupling agent.

[0014] S2: Modify the surface of the fiber. Immerse the blended fiber (carbon fiber, glass fiber and nanofiber) in the chemical coupling agent solution for 1 - 2 hours to enhance the bonding strength between the fiber and the polymer matrix; At the same time, disperse the nano-reinforcing particles (nano-silica, nano-silicon carbide and nano-aluminum oxide) in an appropriate amount of ethanol solution and perform ultrasonic treatment for 30 - 60 minutes to prevent particle agglomeration.

[0015] S3: Mix the polymer matrix material (a mixture of polyimide and epoxy resin), the pretreated blended fiber, the solid self-lubricating particles and the nano-reinforcing particles evenly in proportion; Put the mixed material into a twin-screw extruder and perform melt kneading at a temperature of 300 - 450 °C and a pressure of 15 - 30 MPa for 30 - 60 minutes to ensure that the materials are fully mixed and evenly dispersed.

[0016] S4: Sandblast the surface of the variable-speed cam matrix to remove the surface oxide layer and impurities, then clean it with acetone and dry it for standby. Uniformly coat the material after melt-kneading on the surface of the variable-speed cam through a precision coating device, and use ultrasonic vibration assistance during the coating process with a vibration frequency of 20 - 40 kHz to improve the uniformity and density of the coating; Coat a thin layer of polymer matrix material on the surface of the variable-speed cam matrix to form a diffusion layer with a thickness of 20 - 50 μm, and make it form a chemical bond with the matrix through thermal diffusion treatment; Coat a mixture composed of polymer matrix material, a small amount of reinforcing particles and fibers on the diffusion layer to form a transition layer with a thickness of 30 - 70 μm; Coat the remaining composite material on the transition layer to form a working layer, and its thickness accounts for 40% - 50% of the total thickness.

[0017] S5: Put the coated variable-speed cam into a temperature-controlled oven and carry out curing treatment at a heating rate of 50 - 80 °C / h until it is completely cured. The density of the cured wear-resistant layer should reach 1.2 - 1.6 g / cm³.

[0018] S6: Use laser processing or chemical etching technology to process a bionic friction surface with tiny pits and protrusions on the outer surface of the wear-resistant layer. The depth of the pits is 10 - 30 μm, and the spacing is 50 - 100 μm.

[0019] S7: Process an annular sealing groove on the outer edge of the wear-resistant layer. The cross-section of the sealing groove is V-shaped, with a depth of 0.5 - 1.5 mm and a width of 2 - 4 mm; embed an oil-resistant and wear-resistant elastic sealing ring in the sealing groove. The material of the sealing ring is a blend of silicone rubber and nitrile rubber with a weight ratio of 1 - 2:1.

[0020] The beneficial effects of this technical solution are: (1) This invention uses a mixture of polyimide and epoxy resin as the polymer matrix material, making full use of the high-temperature resistance of polyimide and the bonding performance of epoxy resin to form complementary advantages. This composite matrix material not only improves the mechanical strength of the wear-resistant layer but also enhances its stability in high-temperature environments, significantly superior to a single material system.

[0021] (2) Blended fibers (carbon fiber, glass fiber, and nanofiber), solid self-lubricating particles (graphite, tungsten disulfide, and polytetrafluoroethylene), and nano-reinforcing particles (nano-silica, nano-silicon carbide, and nano-aluminum oxide) are added to the wear-resistant layer. Through the synergistic effect of these components, the comprehensive performance of the wear-resistant layer is significantly improved. The blended fibers provide high strength and impact resistance, the solid self-lubricating particles reduce the friction coefficient, and the nano-particles enhance the hardness and anti-abrasive wear performance; The application of chemical coupling agents, through surface modification of fibers with silane coupling agents and aluminate coupling agents, significantly enhances the bonding strength between the fibers and the polymer matrix. This surface modification treatment effectively solves the problems of poor bonding and easy delamination between fibers and the matrix in the prior art, and improves the overall performance and service life of the wear-resistant layer.

[0022] (3) The wear-resistant layer adopts a multi-layer gradient structure design of a diffusion layer, a transition layer and a working layer. This structure realizes a progressive combination of the wear-resistant layer and the variable-speed cam matrix, avoiding delamination or peeling problems caused by interfacial stress concentration in a single material layer. The diffusion layer forms a chemical bond with the matrix through thermal diffusion treatment, the transition layer plays a buffering and transitional role, and the working layer provides excellent wear resistance. This structural design is relatively rare in the prior art and significantly improves the bonding strength and reliability of the wear-resistant layer.

[0023] (4) The outer surface of the wear-resistant layer is designed as a bionic friction surface with micro-pits and protrusions. The depth and spacing of the pits are precisely optimized, which can effectively store lubricating oil and capture wear debris generated by friction, reducing abrasive wear. This bionic design not only reduces the friction coefficient but also extends the lubrication cycle, significantly superior to the wear-resistant layer with a traditional smooth surface or a single texture design; An annular sealing groove is provided at the outer edge of the wear-resistant layer, and an oil-resistant and wear-resistant elastic sealing ring is embedded. This design effectively prevents lubricating oil leakage and the entry of external impurities, improving the sealing performance and reliability of the variable-speed cam. Compared with the simple sealing methods in the prior art, the sealing groove and sealing ring design of the present invention is more scientific and can significantly extend the service life of the cam.

[0024] (5) Self-lubricating performance and reduction of friction coefficient: The addition of solid self-lubricating particles and the design of the bionic friction surface significantly reduce the friction coefficient and reduce the energy loss in mechanical transmission. Compared with the prior art, the wear-resistant layer of the present invention can still maintain a low friction coefficient under dry friction and insufficient lubrication conditions, improving the mechanical transmission efficiency; The addition of nano-enhanced particles and the design of the multi-layer gradient structure significantly improve the fatigue resistance and reliability of the wear-resistant layer. During long-term operation, the wear-resistant layer can withstand repeated frictional stresses without being easily damaged, significantly superior to the single-material coating in the prior art.

[0025] (6) The composite matrix material of polyimide and epoxy resin has excellent high-temperature resistance. At the same time, the addition of solid self-lubricating particles and nano-enhanced particles further improves the chemical stability of the wear-resistant layer. This high-performance wear-resistant layer is not only suitable for normal temperature environments but also can operate stably under harsh conditions such as high temperature and corrosive media, significantly broadening its application range. Description of the Drawings

[0026] Figure 1Comparison table of experimental data for each embodiment of a polymer wear-resistant layer on the surface of a variable-speed cam and its preparation method proposed by the present invention; Figure 2 Comparison table of wear resistance between a polymer wear-resistant layer on the surface of a variable-speed cam and its preparation method proposed by the present invention and the prior art; Figure 3 Comparison table of bonding strength between a preparation method of a polymer wear-resistant layer on the surface of a variable-speed cam proposed by the present invention and the prior art; Figure 4 Comparison table of lubrication performance between a preparation method of a polymer wear-resistant layer on the surface of a variable-speed cam proposed by the present invention and the prior art. Specific embodiments

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] The specific implementation process is as follows: Embodiment 1: Please refer to Figures 1-4 , a technical solution provided by the present invention: a polymer wear-resistant layer on the surface of a variable-speed cam, including a variable-speed cam base body, a wear-resistant layer is provided on the outer surface of the variable-speed cam base body, and the wear-resistant layer is composed of the following components by weight percentage: 40%-60% of a polymer matrix material, 20%-35% of a blended fiber, 10%-20% of a solid self-lubricating particle, and 5%-15% of a nano-enhancing particle; The polymer matrix material includes a mixture of polyimide and epoxy resin, and the weight ratio of the polyimide to epoxy resin mixture is 1:0.5-1.5. Polyimide has excellent high-temperature resistance and mechanical strength, while epoxy resin has good adhesion and toughness. After mixing the two, the advantages of both can be combined to provide stable matrix support for the wear-resistant layer; The blended fiber includes a mixture of carbon fiber, glass fiber and nanofiber. The weight ratio of the carbon fiber, glass fiber and nanofiber mixture in the blended fiber is 2-3:1-2:1. Carbon fiber has the characteristics of high strength and low density, glass fiber can provide good impact resistance, and nanofiber can enhance the interfacial bonding strength between the fiber and the matrix. After mixing the three, the mechanical properties and wear resistance of the wear-resistant layer can be significantly improved; The solid self-lubricating particles include composite particles composed of graphite, tungsten disulfide and polytetrafluoroethylene. The weight ratio of each component is 1-2:0.5-1:1-1.5. Graphite and tungsten disulfide have good self-lubricating properties, while polytetrafluoroethylene has excellent wear resistance and chemical stability. The addition of the composite particles can effectively reduce the friction coefficient and reduce wear; The nano-enhanced particles include a mixture of nano-silica, nano-silicon carbide and nano-aluminum oxide. The weight ratio of each component is 1-2:1:0.5-1. The addition of the nano-particles can significantly improve the hardness and abrasive wear resistance of the wear-resistant layer, and at the same time improve the toughness and fatigue resistance of the material; The surface of the polymer matrix material and the blended fiber is modified by a chemical coupling agent. The chemical coupling agent is a composite of a silane coupling agent and an aluminate coupling agent. The weight ratio of the silane coupling agent to the aluminate coupling agent is 1-2:1. The use of the chemical coupling agent can enhance the bonding strength between the fiber and the polymer matrix and improve the overall performance of the wear-resistant layer; The thickness of the wear-resistant layer is 0.3-0.8 mm. The outer surface of the wear-resistant layer is designed as a bionic friction surface with micro-pits and protrusions. The depth of the micro-pits is 10-30 μm, and the spacing is 50-100 μm, which can effectively store lubricating oil and capture wear debris generated by friction, reducing abrasive wear; The bonding surface between the inner surface of the wear-resistant layer and the variable-speed cam matrix is a multi-layer gradient structure, which is successively a diffusion layer, a transition layer and a working layer from the inside to the outside. The thickness of the diffusion layer is 20-50 μm, the thickness of the transition layer is 30-70 μm, and the thickness of the working layer accounts for 40%-50% of the total thickness of the wear-resistant layer. The design of the multi-layer gradient structure can achieve a gradual combination of the wear-resistant layer and the matrix, improving the bonding strength and reliability; An annular sealing groove is provided at the outer edge of the wear-resistant layer. The cross-section of the sealing groove is V-shaped, with a depth of 0.5-1.5 mm and a width of 2-4 mm. An oil-resistant and wear-resistant elastic sealing ring is embedded in the sealing groove. The material of the sealing ring is a blend of silicone rubber and nitrile rubber, and the weight ratio of the two is 1-2:1. The design of the sealing groove and the sealing ring can effectively prevent lubricating oil leakage and the entry of external impurities, extending the service life of the cam.

[0029] Example Two: Please refer to Figures 1-4 , a technical solution provided by the present invention: A preparation method for a polymer wear-resistant layer on the surface of a variable-speed cam, comprising the following steps: S1: Prepare polyimide and epoxy resin, and mix them evenly according to a weight ratio of 1:0.5-1.5 to form a polymer matrix material; Prepare carbon fiber, glass fiber and nanofiber, and mix them in a weight ratio of 2 - 3:1 - 2:1 to form blended fiber; prepare graphite, tungsten disulfide and polytetrafluoroethylene, and mix them in a weight ratio of 1 - 2:0.5 - 1:1 - 1.5 to form solid self-lubricating particles; Prepare nano-silica, nano-silicon carbide and nano-aluminum oxide, and mix them in a weight ratio of 1 - 2:1:0.5 - 1 to form nano-reinforcing particles; prepare silane coupling agent and aluminate coupling agent, and mix them in a weight ratio of 1 - 2:1 for standby to form chemical coupling agent; S2: Modify the fiber surface. Immerse the blended fiber (carbon fiber, glass fiber and nanofiber) in the chemical coupling agent solution for 1 - 2 hours to enhance the bonding strength between the fiber and the polymer matrix; meanwhile, disperse the nano-reinforcing particles (nano-silica, nano-silicon carbide and nano-aluminum oxide) in an appropriate amount of ethanol solution and perform ultrasonic treatment for 30 - 60 minutes to prevent particle agglomeration; S3: Mix the polymer matrix material (a mixture of polyimide and epoxy resin), the pretreated blended fiber, the solid self-lubricating particles and the nano-reinforcing particles evenly in proportion; put the mixed material into a twin-screw extruder and perform melt kneading at a temperature of 300 - 450 °C and a pressure of 15 - 30 MPa for 30 - 60 minutes to ensure that the materials are fully mixed and evenly dispersed; S4: Perform sandblasting on the surface of the variable-speed cam matrix to remove the surface oxide layer and impurities, then clean it with acetone and dry it for standby; evenly coat the melt-kneaded material on the surface of the variable-speed cam through a precision coating device, and use ultrasonic vibration assistance during the coating process with a vibration frequency of 20 - 40 kHz to improve the uniformity and density of the coating; Coat a thin layer of polymer matrix material on the surface of the variable-speed cam matrix to form a diffusion layer with a thickness of 20 - 50 μm, and make it form a chemical bond with the matrix through heat diffusion treatment; Coat a mixture composed of polymer matrix material, a small amount of reinforcing particles and fibers on the diffusion layer to form a transition layer with a thickness of 30 - 70 μm; Coat the remaining composite material on the transition layer to form a working layer, and its thickness accounts for 40% - 50% of the total thickness, S5: Put the coated variable-speed cam into a temperature-controlled oven and perform curing treatment at a heating rate of 50 - 80 °C / h until it is completely cured. The density of the cured wear-resistant layer should reach 1.2 - 1.6 g / cm³; S6: Use laser processing or chemical etching technology to machine a bionic friction surface with tiny pits and protrusions on the outer surface of the wear-resistant layer. The depth of the pits is 10 - 30 μm and the spacing is 50 - 100 μm; S7: Machine an annular sealing groove at the outer edge of the wear-resistant layer. The cross-section of the sealing groove is V-shaped, with a depth of 0.5 - 1.5 mm and a width of 2 - 4 mm. Embed an oil-resistant and wear-resistant elastic sealing ring in the sealing groove. The material of the sealing ring is a blend of silicone rubber and nitrile rubber, with a weight ratio of 1 - 2:1.

[0030] Example 3: Please refer to Figures 1-4 , a technical solution provided by the present invention: A method for preparing a polymer wear-resistant layer on the surface of a variable-speed cam, comprising the following steps: S1: In the raw material preparation stage, polyimide and epoxy resin are respectively subjected to vacuum drying treatment, dried at 80 °C for 4 hours to remove moisture and other impurities, ensure the stability of material properties, accurately weigh them according to a weight ratio of 1:0.5, place them in a high-speed stirrer, and stir at 800 revolutions per minute for 30 minutes to mix evenly. Carbon fiber, glass fiber, and nanofiber are dried in an oven at 60 °C for 2 hours, then weighed according to a weight ratio of 2:1:1, put into a fiber mixer, and mixed at 500 revolutions per minute for 20 minutes. Graphite, tungsten disulfide, and polytetrafluoroethylene are ground in an agate mortar for 30 minutes to make their particle sizes more uniform. After weighing according to a weight ratio of 1:0.5:1, ball mill them for 1 hour to mix. Nano-silica, nano-silicon carbide, and nano-aluminum oxide are preliminarily dispersed in an ultrasonic disperser at 40 kHz for 15 minutes, and then weighed and mixed according to a weight ratio of 1:1:0.5. After mixing the silane coupling agent and aluminate coupling agent according to a weight ratio of 1:1, add an appropriate amount of absolute ethanol to prepare a coupling agent solution with a mass fraction of 5%; S2: Immerse the blended fiber completely in the coupling agent solution, soak it at a constant water bath temperature of 50 °C for 1 hour, and stir it every 15 minutes during this period to ensure that the fiber surface is fully grafted with the coupling agent. The nano-enhanced particles are dispersed in an appropriate amount of ethanol solution, and ultrasonically treated in an ultrasonic cleaner at 40 kHz for 30 minutes. During the ultrasonic process, use a temperature control device to keep the solution temperature at 30 °C to prevent the particles from agglomerating due to excessive temperature; S3: Add the mixed polymer matrix material, pretreated blended fiber, solid self-lubricating particles, and nano-enhanced particles to a high-speed mixer in sequence, stir at 1000 revolutions per minute for 45 minutes. Preheat the twin-screw extruder to 300 °C in advance, add the mixed material to the hopper, and melt and knead it at a pressure of 15 MPa for 30 minutes. Real-time monitor the screw torque through a torque sensor to ensure that the material is evenly mixed, and control the torque fluctuation within ±5%; S4: The variable-speed cam base is sandblasted with 80-mesh brown fused alumina, with a sandblasting pressure of 0.5 MPa and a sandblasting time of 10 minutes to remove the surface oxide layer and impurities. Immediately after sandblasting, it is ultrasonically cleaned with acetone for 15 minutes, and then placed in an 80°C oven and dried for 2 hours. The precision coating equipment uses a thermal spraying process, with a spraying distance of 150 mm and a spraying temperature of 350°C. With the assistance of an ultrasonic vibration frequency of 20 kHz, a 20-μm diffusion layer is first evenly sprayed with a polymer matrix material. During the spraying process, an infrared thermometer is used to monitor the coating temperature to ensure that the temperature is between 300 - 320°C. Then, the material ratio is adjusted through the spray gun, and a mixture composed of the polymer matrix material, a small amount of reinforcing particles, and fibers is sprayed to form a 30-μm transition layer. Finally, the remaining composite material is sprayed to form a working layer that accounts for 40% of the total thickness; S5: The coated variable-speed cam is placed in a temperature-controlled oven and heated from room temperature to 180°C at a heating rate of 50°C / h and held for 2 hours for curing. During the curing process, the pressure change is monitored through a pressure sensor in the oven, and the pressure is maintained at 0.1 - 0.12 MPa; S6: A pulsed laser processing equipment is used, with a laser wavelength of 1064 nm, a pulse width of 10 ns, and a frequency of 10 kHz. A bionic friction surface with a pit depth of 10 μm and a pitch of 50 μm is processed on the outer surface of the wear-resistant layer. Before processing, the laser equipment is calibrated for the light spot to ensure the processing accuracy; S7: Using a CNC machining center and a V-shaped milling cutter, a V-shaped sealing groove with a depth of 0.5 mm and a width of 2 mm is machined. During the machining process, the milling speed is controlled at 800 revolutions per minute, and the feed rate is 0.1 mm per revolution. Silicone rubber and nitrile rubber are kneaded on an open mill for 30 minutes according to a weight ratio of 1:1, and then vulcanized and formed through a mold to make a sealing ring embedded in the sealing groove; It can be obtained according to the above steps: Wear resistance: Simulating the working environment of the variable-speed cam, a test platform is built on a friction and wear testing machine. The ambient temperature is controlled at 25°C, the relative humidity is 50%, the friction pair material is selected as GCr15 bearing steel with a hardness of HRC60, a vertical load of 50 N is applied, and the friction speed is 0.5 m / s. A 1000-cycle friction test is carried out. Before the test, the sample mass is weighed with an electronic balance with a precision of 0.0001 g, and it is weighed again after the test. The difference between the two masses is the wear amount of 0.05 g. Each weighing is repeated 3 times, and the average value is taken, with the error controlled within ±0.001 g; Bond strength: Tensile specimens were fabricated with dimensions conforming to ASTM D638 standards and tested on a universal materials testing machine at a tensile rate of 5 mm / min. The force value during the tensile process was measured through a force sensor. When the specimen failed, the maximum force value was recorded, and the bond strength was calculated based on the cross-sectional area of the specimen. The calculation formula is: Bond strength = Maximum force value / Cross-sectional area of the specimen. The calculated result was 10 MPa. Five specimens were tested in each group, and the average value was taken with the error controlled within ±0.5 MPa. Lubrication performance: The variable-speed cam with a wear-resistant layer was placed into a self-made lubrication performance testing device, and an appropriate amount of lubricating oil (model ISOVG32) was injected into the device. Microscopic pits were observed through an optical microscope. Randomly selecting 100 pits, the number of pits storing lubricating oil was counted, and the storage rate was calculated to be 80%. This was repeated three times with the error controlled within ±3%. During the friction test, a laser particle size analyzer was installed at the oil outlet of the testing device to detect the number of wear debris. By comparing the change in the number of wear debris before and after friction, the wear debris capture rate was calculated to be 70%, and the measurement error was controlled within ±5%. In the polymer matrix material, polyimide and epoxy resin were mixed at a ratio of 1:0.5, accounting for 40%, which balanced the cost and performance to a certain extent. The blended fiber accounted for 20%, the solid self-lubricating particles accounted for 10%, and the nano-enhanced particles accounted for 5%. Through a series of relatively basic preparation processes, such as melt kneading in a twin-screw extruder at 300 °C, etc., it finally exhibited a wear amount of 0.05 g after 1000 cycles of friction, a bond strength of 10 MPa, a lubricating oil storage rate of 80%, and a wear debris capture rate of 70%.

[0031] Example 4: Please refer to Figures 1-4 , a technical solution provided by the present invention: A method for preparing a polymer wear-resistant layer on the surface of a variable-speed cam, comprising the following steps: S1: Polyimide and epoxy resin were vacuum-dried at 100 °C for 5 hours. After weighing according to a weight ratio of 1:1, they were mixed in a planetary mixer at 1200 revolutions per minute for 40 minutes. Various fibers were dried in an oven at 70 °C for 2.5 hours. After weighing according to a weight ratio of 2.5:1.5:1, they were mixed in a three-dimensional mixer for 25 minutes. The solid self-lubricating particles were ground and ball-milled, and then mixed after weighing according to a weight ratio of 1.5:0.75:1.25. The nano-enhanced particles were ultrasonically dispersed and then mixed according to a weight ratio of 1.5:1:0.75. The silane coupling agent and aluminate coupling agent were mixed according to a weight ratio of 1.5:1 to prepare a coupling agent solution with a mass fraction of 6%. S2: The blended fiber was soaked in the coupling agent solution in a 60 °C constant-temperature water bath for 1.5 hours, with stirring every 20 minutes. The nano-enhanced particles were ultrasonically treated in an ultrasonic cleaner at 40 kHz for 45 minutes, with the temperature controlled at 35 °C. S3: Stir and mix all components in a high-speed mixer at 1200 revolutions per minute for 50 minutes. Preheat the twin-screw extruder to 375 °C and perform melt kneading at a pressure of 22.5 MPa for 45 minutes, with the torque fluctuation controlled within ±4%; S4: Use white fused alumina with 100 meshes for matrix sandblasting, with a pressure of 0.6 MPa and a time of 12 minutes. Ultrasonically clean with acetone for 20 minutes, dry in an oven at 90 °C for 2.5 hours. For precision coating, use the plasma spraying process, with a spraying distance of 180 mm, a temperature of 400 °C, an ultrasonic vibration frequency of 25 kHz, a diffusion layer of 35 μm, a transition layer of 50 μm, and the working layer accounting for 45% of the total thickness. During the spraying process, monitor the coating temperature in real-time at 320 - 350 °C; S5: The temperature-controlled oven is heated from room temperature to 200 °C at a rate of 65 °C / h, held for 2.5 hours for curing, and the pressure is maintained at 0.12 - 0.14 MPa; S6: Use a mixed solution of hydrofluoric acid and nitric acid for chemical etching, with an etching time of 5 minutes and a temperature of 20 °C to machine a bionic friction surface with a pit depth of 20 μm and a spacing of 75 μm. After etching, rinse thoroughly with deionized water and dry with nitrogen; S7: Machine the sealing groove on a CNC machining center, with a milling speed of 1000 revolutions per minute and a feed rate of 0.12 mm per revolution. Mix silicone rubber and nitrile rubber in a mixer for 40 minutes, and embed the molded die into the sealing groove after vulcanization; It is obtained according to the above steps: Wear resistance: The test environment temperature of the friction and wear testing machine is 28 °C, the relative humidity is 45%, the friction pair material is 42CrMo alloy steel, the hardness is HRC45, the vertical load is 60 N, the friction speed is 0.6 m / s, and 1000 cycles of friction tests are carried out. Weigh with an electronic balance with a precision of 0.0001 g, and the wear amount is 0.03 g. Repeat 3 times, with the error controlled within ±0.001 g; Bonding strength: Make specimens according to the ASTM D638 standard, with a tensile rate of 6 mm / min on a universal material testing machine, and calculate the bonding strength to be 12 MPa. There are 5 specimens in each group, and the error is controlled within ±0.5 MPa; Lubrication performance: Inject ISOVG46 lubricating oil into the lubrication performance testing device, observe 150 pits under a microscope to calculate the storage rate of 85%, repeat 3 times, with the error controlled within ±3%. Detect the wear debris with a laser particle size analyzer and calculate the wear debris capture rate of 75%, with the error controlled within ±5%; The proportion of each component is at a medium level. The proportion of the polymer matrix material is increased to 50%, the blended fiber accounts for 25%, the solid self-lubricating particles account for 15%, and the nano-enhanced particles account for 10%. The preparation process parameters are optimized. For example, the temperature of the twin-screw extruder is increased to 375°C, and the curing heating rate is adjusted to 65°C / h. Its performance shows a wear amount of 0.03 g, a bonding strength of 12 MPa, a lubricating oil storage rate of 85%, and a wear debris capture rate of 75%. All performances are improved compared with Example 3.

[0032] Example Five: Please refer to Figures 1-4 , a technical solution provided by the present invention: a method for preparing a polymer wear-resistant layer on the surface of a variable-speed cam, comprising the following steps: S1: Polyimide and epoxy resin are vacuum-dried at 120°C for 6 hours. After weighing according to a weight ratio of 1:1.5, they are mixed in a double planetary mixer at 1500 revolutions per minute for 50 minutes. The fibers are dried in an 80°C oven for 3 hours. After weighing according to a weight ratio of 3:2:1, they are mixed in a high-strength mixer for 30 minutes. The pretreatment of the solid self-lubricating particles and nano-enhanced particles before mixing in proportion is the same as before. Silane coupling agent and aluminate coupling agent are mixed according to a weight ratio of 2:1 to prepare a coupling agent solution with a mass fraction of 7%. S2: The blended fiber is soaked in the coupling agent solution in a 70°C constant temperature water bath for 2 hours, and stirred every 25 minutes. The nano-enhanced particles are ultrasonically treated in an ultrasonic cleaner at 40 kHz for 60 minutes, and the temperature is controlled at 40°C. S3: Stir and mix all components in a high-speed mixer at 1500 revolutions per minute for 60 minutes. The twin-screw extruder is preheated to 450°C and melt-kneaded at 30 MPa for 60 minutes, and the torque fluctuation is controlled within ±3%. S4: For the matrix sandblasting, 120-mesh silicon carbide sand is used, the pressure is 0.7 MPa, and the time is 15 minutes. It is ultrasonically cleaned with acetone for 25 minutes and dried in a 100°C oven for 3 hours. Precision coating adopts the supersonic flame spraying process, the spraying distance is 200 mm, the temperature is 450°C, the ultrasonic vibration frequency is 40 kHz, the diffusion layer is 50 μm, the transition layer is 70 μm, the working layer accounts for 50% of the total thickness, and the spraying temperature is controlled at 350-380°C. S5: The temperature-controlled oven is heated from room temperature to 220°C at a rate of 80°C / h, held for 3 hours for curing, and the pressure is maintained at 0.14-0.16 MPa. S6: Laser processing uses a picosecond laser device with a wavelength of 532 nm, a pulse width of 100 ps, and a frequency of 20 kHz to process a bionic friction surface with a pit depth of 30 μm and a spacing of 100 μm. The optical path of the equipment is calibrated before processing. S7: The sealing groove is machined on a CNC machining center at a milling speed of 1200 revolutions per minute and a feed rate of 0.15 mm per revolution. The silicone rubber and nitrile rubber are kneaded in a screw extruder for 50 minutes, and after the mold is vulcanized and formed, it is embedded in the sealing groove; It is obtained according to the above steps: Wear resistance: The test environment temperature of the friction and wear testing machine is 30 °C, the relative humidity is 40%, the friction pair material is cemented carbide with a hardness of HRA85, the vertical load is 70 N, the friction speed is 0.7 m / s, and 1000 cycles of friction tests are carried out. The precision of the electronic balance is 0.0001 g, the wear amount is 0.02 g, repeated 3 times, and the error is controlled within ±0.001 g; Bonding strength: Specimens are made according to ASTM D638 standard, the tensile rate of the universal material testing machine is 8 mm / min, and the calculated bonding strength is 15 MPa. There are 5 specimens in each group, and the error is controlled within ±0.5 MPa; Lubrication performance: The lubrication performance test device is filled with ISO VG68 lubricating oil. The storage rate is calculated as 90% by observing 200 pits under a microscope, repeated 3 times, and the error is controlled within ±3%. The wear debris is detected by a laser particle size analyzer, and the wear debris capture rate is calculated as 80%, and the error is controlled within ±5%; Taking the upper limit of the proportion of each component, the polymer matrix material accounts for 60%, the blended fiber accounts for 35%, the solid self-lubricating particles account for 20%, and the nano-enhanced particles account for 15%. The preparation process adopts high-temperature, high-pressure and long-time treatment, such as melting and kneading in a twin-screw extruder at 450 °C for 60 minutes, with the best performance, the wear amount is only 0.02 g, the bonding strength is 15 MPa, the lubricating oil storage rate is 90%, and the wear debris capture rate is 80%; After 1000 cycles of friction, the wear amount of the existing ordinary wear-resistant coating is 0.1 - 0.15 g, and the wear amount of some improved wear-resistant coatings is 0.06 - 0.08 g. The wear amounts of Examples 3 - 5 of the present invention are 0.05 g, 0.03 g, and 0.02 g respectively. This is because the polymer matrix material, blended fiber, solid self-lubricating particles and nano-enhanced particles of the present invention cooperate with each other to form a denser and more wear-resistant structure. For example, the nano-enhanced particles refine the microstructure of the material, improve the hardness and wear resistance of the material, thus significantly reducing the wear amount and extending the service life of the variable-speed cam; The bonding strength of the existing ordinary wear-resistant coating is 5 - 8 MPa, and that of some improved wear-resistant coatings is 8 - 10 MPa. The bonding strengths of Examples 3 - 5 of the present invention are 10 MPa, 12 MPa, and 15 MPa respectively. The present invention modifies the fiber surface through a chemical coupling agent, enhances the bonding force between the fiber and the polymer matrix, and at the same time, the design of the multi-layer gradient structure, from the diffusion layer, transition layer to the working layer, gradually enhances the bonding with the matrix, making the wear-resistant layer not easy to fall off during use, and ensuring the reliability and stability of the coating; The storage rate of existing ordinary wear-resistant coating lubricants is 40%-60%, and the chip capture rate is 30%-50%; the storage rate of some improved wear-resistant coating lubricants is 60%-70%, and the chip capture rate is 50%-60%. The storage rates of the lubricants in Examples 3-5 of the present invention are 80%, 85%, and 90% respectively, and the chip capture rates are 70%, 75%, and 80% respectively. The bionic friction surface design on the outer surface of the wear-resistant layer and the reasonable sizes of the micro-pits and protrusions effectively store the lubricant, and at the same time can better capture the chips generated by friction, reduce abrasive wear, improve the lubrication performance, reduce the friction coefficient, and further improve the working efficiency and service life of the speed-changing cam.

[0033] The above are only the embodiments of the present invention. Specific technical solutions or common knowledge such as characteristics known in the solutions are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A polymer wear-resistant layer on the surface of a speed change cam, comprising a speed change cam substrate, characterized in that: The outer surface of the speed change cam substrate is provided with a wear-resistant layer, and the wear-resistant layer is composed of the following components by weight percentage: 40%-60% of high molecular polymer matrix material, 20%-35% of blended fiber, 10%-20% of solid self-lubricating particles, and 5%-15% of nano-enhanced particles; The high molecular polymer matrix material includes a mixture of polyimide and epoxy resin, and the weight ratio of the polyimide to epoxy resin mixture is 1:0.5-1.5; The blended fiber comprises a mixture of carbon fiber, glass fiber and nanofiber, and the weight ratio of the mixture of carbon fiber, glass fiber and nanofiber in the blended fiber is 2-3:1-2:1; The solid self-lubricating particles include composite particles composed of graphite, tungsten disulfide and polytetrafluoroethylene, and the weight ratio of each component is 1-2:0.5-1:1-1.5; The nano-enhanced particles include a mixture of nano-silicon dioxide, nano-silicon carbide and nano-aluminum oxide, and the weight ratio of each component is 1-2:1:0.5-1.

2. The polymer wear-resistant layer on the surface of a speed change cam according to claim 1, characterized in that: The high molecular polymer matrix material and the blended fiber are subjected to surface modification treatment by using a chemical coupling agent, wherein the chemical coupling agent is a composite of a silane coupling agent and an aluminate coupling agent, and the weight ratio of the silane coupling agent to the aluminate coupling agent is 1-2:

1.

3. The polymer wear-resistant layer on the surface of a speed change cam according to claim 1, characterized in that: The thickness of the wear-resistant layer is 0.3-0.8 mm, and the outer surface of the wear-resistant layer is designed as a bionic friction surface with tiny pits and protrusions. The depth of the tiny pits is 10-30 μm, and the spacing is 50-100 μm, which can effectively store lubricating oil and capture the wear debris generated by friction, thereby reducing abrasive wear; The bonding surface between the inner surface of the wear-resistant layer and the speed-changing cam substrate is a multi-layer gradient structure, which includes a diffusion layer, a transition layer and a working layer from the inside to the outside. The thickness of the diffusion layer is 20-50 μm, the thickness of the transition layer is 30-70 μm, and the thickness of the working layer accounts for 40%-50% of the total thickness of the wear-resistant layer.

4. The polymer wear-resistant layer on the surface of a speed change cam according to claim 1, characterized in that: An annular sealing groove is provided on the outer edge of the wear-resistant layer. The cross-section of the sealing groove is V-shaped, the depth is 0.5-1.5mm, and the width is 2-4mm. An oil-resistant and wear-resistant elastic sealing ring is embedded in the sealing groove. The material of the sealing ring is a blend of silicone rubber and nitrile rubber, and the weight ratio of the two is 1-2:

1.

5. A method for preparing a polymer wear-resistant layer on the surface of a speed change cam, characterized in that: The following steps are involved: S1: preparing polyimide and epoxy resin, and mixing them evenly in a weight ratio of 1:0.5-1.5 to form a high molecular polymer matrix material; Prepare carbon fiber, glass fiber and nanofiber, and mix them in a weight ratio of 2-3:1-2:1 to form a blended fiber; Prepare graphite, tungsten disulfide and polytetrafluoroethylene, and mix them in a weight ratio of 1-2:0.5-1:1-1.5 to form solid self-lubricating particles; Prepare nano-silicon dioxide, nano-silicon carbide and nano-aluminum oxide, and mix them in a weight ratio of 1-2:1:0.5-1 to form nano-reinforced particles; Prepare a silane coupling agent and an aluminate coupling agent, and mix them in a weight ratio of 1-2:1 to form a chemical coupling agent; S2: Modify the fiber surface by immersing the blended fibers (carbon fiber, glass fiber and nanofiber) in a chemical coupling agent solution for 1-2 hours to enhance the bonding strength between the fiber and the polymer matrix; Meanwhile, nano-reinforced particles (nano-silicon dioxide, nano-silicon carbide and nano-aluminum oxide) were dispersed in an appropriate amount of ethanol solution and ultrasonically treated for 30-60 minutes to prevent particle agglomeration; S3: mixing the polymer matrix material (mixture of polyimide and epoxy resin), the pretreated blended fibers, the solid self-lubricating particles and the nano-reinforced particles uniformly in proportion; The mixed materials are placed in a twin-screw extruder and melt-kneaded at a temperature of 300-450°C and a pressure of 15-30MPa for 30-60 minutes to ensure that the materials are fully mixed and evenly dispersed; S4: sandblasting the surface of the speed change cam substrate to remove the surface oxide layer and impurities, then cleaning with acetone and drying for later use; The melt-kneaded material in S3 is uniformly coated on the surface of the speed change cam by a precision coating device. Ultrasonic vibration is used to assist in the coating process, and the vibration frequency is 20-40kHz to improve the uniformity and density of the coating; A thin layer of high molecular polymer matrix material is coated on the surface of the speed change cam matrix to form a diffusion layer with a thickness of 20-50 μm, and a thermal diffusion treatment is performed to form a chemical bond with the matrix; A layer of a mixture of a high molecular polymer matrix material and a small amount of reinforcing particles and fibers is coated on the diffusion layer to form a transition layer with a thickness of 30-70 μm; The remaining composite material is coated on the transition layer to form a working layer, the thickness of which accounts for 40%-50% of the total thickness; S5: Place the coated speed cam in a temperature-controlled oven and cure it at a heating rate of 50-80℃ / h until it is completely cured. The density of the wear-resistant layer after curing should reach 1.2-1.6g / cm³; S6: Laser processing or chemical etching technology is used to process tiny pits and raised bionic friction surfaces on the outer surface of the wear-resistant layer. The pit depth is 10-30μm and the spacing is 50-100μm. S7: An annular sealing groove is machined on the outer edge of the wear-resistant layer. The cross section of the sealing groove is V-shaped, with a depth of 0.5-1.5 mm and a width of 2-4 mm; An oil-resistant and wear-resistant elastic sealing ring is embedded in the sealing groove. The sealing ring material is a blend of silicone rubber and nitrile rubber with a weight ratio of 1-2:1.

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