A friction material for a smooth and quiet electromagnetic brake and its preparation method.

Abstract

This invention relates to the field of friction material technology. Addressing the problems of unstable braking, low precision, and high noise during braking in existing industrial robots due to the influence of friction materials, this invention specifically discloses a friction material for electromagnetic brakes that provides smooth and quiet braking, and its preparation method. By mass fraction, it comprises 40-50 wt% friction-enhancing filler, 15-30 wt% reinforcing material, 8-12 wt% binder, 8-15 wt% friction-reducing filler, and 0.5-2 wt% compounding agent. By total mass of the friction material, the reinforcing material includes 1-2 wt% PI / Al₂O₃ composite fiber, and the friction-reducing filler includes 3-5 wt% polyketone and 3-5 wt% Ti₄MoSiB₂. This invention, through improvements in multiple raw materials and their preparation process, and through the synergistic mechanism between PI / Al₂O₃ composite fiber and multiple components such as polyketone and Ti₄MoSiB₂, achieves significant effects such as enhanced noise reduction while maintaining good friction performance.

Description

Technical Field

[0001] This invention relates to the field of friction material technology, and more specifically, to a friction material for electromagnetic brakes that provides smooth and quiet braking, and its preparation method. Background Technology

[0002] Friction materials are widely used in various industries for transmission and braking equipment, such as automotive brakes and clutches. Especially in recent years, with the advent of Industry 4.0, industrial robots have experienced explosive growth, leading to a significant increase in demand for electromagnetic brakes. Electromagnetic brakes, often referred to as the "reflex arc of the industrial nervous system," play a crucial role in precisely transmitting force or torque and controlling motion, making them a key component for the safety, efficiency, and reliability of high-end equipment. Friction pads are the core material of electromagnetic brakes, determining the operational safety, smoothness, and comfort of the equipment and its key components. Because industrial robots require high control precision, smooth operation, and quiet operation, even higher demands are placed on friction materials.

[0003] Currently, existing industrial robots suffer from performance problems such as unstable braking, low precision, and high noise during braking. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of unstable material properties and high noise caused by friction damage during braking in existing industrial robots due to the influence of friction materials.

[0005] This invention is achieved through the following technical solution:

[0006] This invention provides a friction material for electromagnetic brakes that provides smooth and quiet braking. By mass fraction, it comprises 40-50 wt% friction-increasing filler, 15-30 wt% reinforcing material, 8-12 wt% binder, 8-15 wt% friction-reducing filler, and 0.5-2 wt% compounding agent. By total mass of the friction material, the reinforcing material comprises 1-2 wt% PI / Al2O3 composite fiber, and the friction-reducing filler comprises 3-5 wt% polyketone and 3-5 wt% Ti4MoSiB2.

[0007] Preferably, based on the total mass of the friction material, the reinforcing material includes 10-15 wt% mineral fibers, 5-10 wt% magnesium oxide whiskers, 1-3 wt% carbon nanotubes, and 1-2 wt% PI / Al2O3 composite fibers.

[0008] Preferably, the friction-reducing filler comprises 3-5 wt% polyketone, 3-5 wt% Ti4MoSiB2 and 2-4 wt% flake graphite, based on the total mass of the friction material.

[0009] Preferably, based on the total mass of the friction material, the friction-enhancing filler includes 8-12 wt% acicular wollastonite, 6-10 wt% cashew nutshell oil friction powder, 5-10 wt% nano clay, 5-8 wt% cryolite, 5-8 wt% calcium fluoride, 3-6 wt% nano alumina, 1-3 wt% nano silicon carbide, and 0.5-1 wt% carbon black.

[0010] Preferably, the adhesive comprises 5-10 wt% perfluoroether rubber and 2-4 wt% boron-lithium modified phenolic resin, based on the total mass of the friction material.

[0011] Preferably, the mass ratio of polyketone to Ti4MoSiB2 is 1:1, and the mass ratio of PI / Al2O3 composite fiber to the total mass of polyketone and Ti4MoSiB2 is 1~2:6~8.

[0012] The present invention also provides a method for preparing the above-mentioned friction material for a smooth and quiet electromagnetic brake, comprising the following steps:

[0013] S1 Pre-dispersion: Take polyketone, Ti4MoSiB2, and PI / Al2O3 composite fibers according to the specified amounts. First, mix the polyketone and Ti4MoSiB2 with a silane coupling agent and disperse by stirring at 1000-1500 rpm. Then, add the PI / Al2O3 composite fibers and mix them. Put the mixture into an internal mixer and mix at the highest mixing temperature of 50-70℃ for 25-30 minutes to obtain the pre-dispersion material.

[0014] S2 Mixing and mixing: Take the remaining raw materials according to the specified amount, mix and mix them with the pre-dispersed material, then crush and sieve to obtain the mixed granules;

[0015] S3 Cold pressing: The internally mixed granules are cold pressed at 50-60℃ to obtain a cold billet;

[0016] S4 Hot pressing: The cold blank is placed at 150±5℃ for hot pressing to obtain the friction plate;

[0017] S5 Heat treatment: The friction plate is heated in a gradient, held at the temperature, and then cooled in a gradient.

[0018] S6 Post-processing: The friction pads after heat treatment are surface ground to obtain the friction material for the electromagnetic brake.

[0019] Preferably, in step S2, the maximum mixing temperature is 50-80℃ and the mixing time is 10-30 minutes.

[0020] Preferably, in step S3, the cold pressing pressure is 50-60 MPa, and the cold pressing holding time is 20-30 s;

[0021] In step S4, the hot pressing pressure is 40-50 MPa, and the hot pressing holding time is 80-100 s / mm.

[0022] Preferably, in step S5, the specific process of heat treatment is as follows:

[0023] S5.1 Place the friction plate in a heating furnace, heat it from room temperature to 120±5℃ in 50-60 minutes, and keep it at that temperature for 1-2 hours;

[0024] S5.2 After another 30-60 minutes, heat to 180±5℃ and hold for 0.5-1.5 hours;

[0025] After S5.3, heat to 220±5℃ for 30-60 minutes and keep warm for 6-8 hours;

[0026] S5.4 Finally, after 40-50 minutes, the temperature is lowered to 180±5℃, held for 1-2 hours, and then cooled to 50℃ or below in the furnace before being removed.

[0027] The technical solution of the present invention has the following beneficial effects:

[0028] (1) In this invention, polyketone and Ti4MoSiB2 are used as lubricants for high-temperature operating conditions. The ketone group of polyketone forms hydrogen bonds with the hydroxyl group on the surface of TiO2, which strengthens the bonding force between the lubricating phase MoO3 / TiO2 and the polyketone skeleton, thus significantly reducing the wear rate of the composite lubricating layer.

[0029] Under high-temperature conditions of 200-400℃, Ti4MoSiB2 reacts rapidly under frictional heat to generate MoO3 and TiO2, which serve as a layered lubricating phase and a dense protective layer, respectively. MoO3 exhibits excellent lubrication properties, while TiO2 reduces surface resistance. Meanwhile, the polyketone molecule contains strongly polar ketone groups, resulting in strong intermolecular forces that form a physical support framework, anchoring MoO3 / TiO2 particles to the friction surface. This prevents the lubricating phase from being lost or agglomerated at high temperatures, thus solving the defects of traditional lubricants that are prone to failure at high temperatures and adhesion at low temperatures. Furthermore, the polyketone has a high glass transition temperature (Tg), making it less prone to softening or decomposition at high temperatures. It also maintains structural stability at 300-400℃, which can reduce fluctuations in the coefficient of friction.

[0030] Under medium-low temperature conditions not exceeding 200℃, polyketone has a low surface energy, making it less prone to adhesion to mating parts at low temperatures. Simultaneously, its moderate hardness prevents abrasive wear on mating parts caused by excessive material hardness, extending the service life of the mating parts. The repeating ketone groups in the polyketone backbone are strongly polar groups, forming dipole-dipole forces between adjacent molecular chains. The molecular chains are tightly attracted as if magnetically drawn together, making lateral slippage during friction difficult and preventing surface layer peeling wear caused by molecular chain slippage. Polyketone's high crystallinity and stable crystal structure form a macroscopically dense and hard surface layer, effectively resisting the plowing action of mating parts during friction, greatly improving wear resistance, and thus significantly enhancing the stability of the friction coefficient of the friction material.

[0031] (2) The present invention introduces PI / Al2O3 composite fiber into the reinforcing material, which can play a synergistic role in many aspects such as structural support, thermal conductivity and noise reduction.

[0032] The rigid Al2O3 component of the PI / Al2O3 composite fiber forms a microstructure that is uniformly dispersed in the friction material matrix, preventing localized over- or under-lubrication caused by Ti4MoSiB2 particle agglomeration. The toughening component of PI, through a bridging effect, prevents matrix crack propagation and prevents crack penetration that could damage the composite lubrication layer, thus extending its service life. The high thermal conductivity of Al2O3 rapidly conducts frictional heat, homogenizing the friction interface temperature and preventing softening of polyketone due to localized high temperatures. Simultaneously, it provides a stable temperature environment for the controllable reaction of Ti4MoSiB2, ensuring the continuous formation of MoO3 / TiO2. The elastic modulus of PI forms a gradient elastic system with polyketone and Ti4MoSiB2. The PI / Al2O3 fiber absorbs frictional impact energy, polyketone buffers contact stress, and Ti4MoSiB2 reduces dry friction impact. Experimental verification shows that through synergistic effects, these three components can reduce braking noise to 32-35 dB, solving the technical challenge of simultaneously achieving lubrication and noise reduction.

[0033] (3) The present invention uses boron lithium modified phenolic resin and perfluoroether rubber as adhesives.

[0034] Introducing boron into boron-modified phenolic resin restructures the cross-linking structure of the resin molecules, forming higher-energy BO and BC bonds, significantly inhibiting thermal degradation and carbonization loss at high temperatures, and greatly increasing the decomposition temperature of the friction material matrix. Furthermore, while the introduction of boron increases the resin's decomposition temperature, it also reduces its toughness. Therefore, lithium modification is introduced. Lithium ions, with their small radius, can form coordination bonds with hydroxyl and ether bonds in the phenolic resin molecular chain, weakening strong intermolecular forces, increasing chain segment flexibility, and acting as a molecular toughening agent to improve the internal stress distribution of the resin, thereby enhancing the toughness and strength of the matrix. The boron-lithium coordination structure can inhibit the swelling effect of water molecules on the resin, resulting in superior resistance to damp heat compared to traditional phenolic resins. Lithium reduces hydrogen bonding between molecular chains, lowering the resin melt viscosity, improving resin flowability, optimizing its molding properties, and making the cross-linking network more dense and uniform during resin curing. At high temperatures, lithium can promote the formation of a dense, continuous carbon layer during resin combustion, which can also improve the stability of the friction coefficient and wear resistance of the friction material to some extent. Perfluoroelastomer rubber has excellent hydrophobicity. In humid environments, it is not easy for a continuous water film to form on its surface, which can reduce the sudden drop in the coefficient of friction caused by water film lubrication and maintain stable wet friction performance. In medium and low temperature friction scenarios, perfluoroelastomer rubber maintains good elasticity and can compensate for the micro-unevenness after surface wear through elastic contact with the mating parts, reduce the fluctuation of the coefficient of friction, and maintain the stability of the coefficient of friction.

[0035] The main chain of perfluoroether rubber molecules consists of saturated carbon chains of ethylene and propylene, containing only a small number of unsaturated double bonds used for vulcanization. The C-C bonds of the saturated carbon chains have high bond energies and are not easily attacked by oxygen or free radicals at high temperatures. Therefore, the thermo-oxidative degradation rate is extremely slow. Blending with phenolic resins can increase the decomposition temperature of the matrix and reduce fluctuations in the high-temperature friction coefficient.

[0036] (4) This invention introduces nano-clay into the friction-enhancing filler. The lamellar structure of nano-clay has excellent dispersibility, which can uniformly fill the microscopic voids of the matrix during the friction material forming process, reducing the fluctuation of the friction coefficient caused by interface voids during braking; at the same time, its lamellars can form a thin and dense transfer film on the friction surface, similar to a lubrication-wear-resistant buffer layer, avoiding direct rigid friction between the metal mating parts and the friction material. During braking, frictional heat generation will lead to high-temperature decomposition of the material, which will cause the friction coefficient to drop sharply. Nano-clay can maintain structural stability in high-temperature environments, and its lamellars can also hinder the transfer of heat to the interior of the material, delaying the thermal aging of the matrix, thereby reducing the degree of thermal decay; the lamellars of nano-clay have a certain degree of flexibility, which can undergo slight deformation under braking pressure and rebound quickly after unloading, helping the friction material maintain the fit with the mating parts, and keeping the friction coefficient stable while maintaining a large friction coefficient. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are performed according to conventional conditions or conditions recommended by the manufacturer; where the manufacturers of the instruments, equipment, reagents, or raw materials used are not specified, they are all conventional products that can be purchased commercially.

[0038] This invention provides a friction material for an electromagnetic brake that provides smooth and quiet braking, comprising the following components:

[0039] ① 40~50wt% friction-enhancing filler: including 8~12% needle-shaped wollastonite, 6~10% cashew shell oil friction powder, 5~10% nano clay, 5~8% cryolite, 5~8% calcium fluoride, 3~6% nano alumina, 1~3% nano silicon carbide and 0.5~1% carbon black.

[0040] Among them, nano clay includes one or more of nano montmorillonite, nano kaolinite, and nano attapulgite.

[0041] ② 15~30wt% reinforcing materials: including 10~15wt% mineral fibers, 5~10wt% magnesium oxide whiskers, 1~3wt% carbon nanotubes and 1~2wt% PI / Al2O3 composite fibers.

[0042] The PI / Al2O3 composite fiber can be prepared using existing processes, such as coaxial coating vapor deposition combined with electrospinning. The preparation method includes the following steps:

[0043] a1. Dissolve 1.84 g of 4,4'-diaminodiphenyl ether in 30 mL of N,N-dimethylformamide. Place the solution under a mechanical stirrer and stir at 300 rpm at room temperature for about 30 min until completely dissolved. Set up an ice-water bath and control the temperature at 0-5℃ to avoid high-temperature polymerization of the monomer. Add 2.0 g of pyromellitic dianhydride slowly to the solution in multiple portions, with an interval of 10 min between each addition to prevent local overheating and a sudden increase in viscosity. After the addition is complete, increase the stirring speed to 500 rpm and continue stirring for 2 h to obtain a polyamic acid (PAA) spinning solution. Let it stand for 30 min to remove bubbles and then fill a 20 mL syringe with a No. 12 stainless steel needle for later use.

[0044] a2. Start the electrospinning machine and set the parameters as follows: spinning voltage 17kV, spinning rate 0.5mL / h, receiving distance 20cm, receiving roller speed 400rpm. Start spinning at room temperature and run continuously for 4h. A PAA nanofiber membrane with a thickness of about 130±15μm can be collected. Peel it off from the roller and place it in a clean bench. Let it stand for 12h in a windless environment at room temperature.

[0045] a3. After the PAA fiber membrane has been allowed to stand, lay it flat on the quartz stage of the plasma cleaner, close the chamber door, evacuate to 10 Pa, introduce oxygen until the pressure returns to 50 Pa, set the power to 80%, start the plasma, process for 5 minutes, then turn off the equipment and remove it.

[0046] a4. Spread 8g of aluminum isopropoxide evenly on the bottom of the vacuum dryer to form a thin layer, ensuring uniform evaporation; use quartz clamps to suspend and fix the above-treated PAA fiber membrane inside the dryer, about 10cm away from the aluminum isopropoxide layer, to avoid direct contact that could lead to excessive local coating; close the dryer door, use a vacuum pump to evacuate to -0.095MPa, then put on a heating jacket, raise the temperature to 150℃, and keep it at that temperature for 1 hour to ensure that the aluminum isopropoxide vapor is fully adsorbed onto the PAA fiber surface; close the heating jacket, allow it to cool naturally to room temperature, slowly release the gas, and remove the modified PAA fiber membrane coated with aluminum isopropoxide.

[0047] a5. The modified PAA fiber membrane was placed in a ceramic boat and placed in a muffle furnace. Nitrogen gas was introduced at 50 mL / min to purge the air. The heating process in the furnace was controlled as follows: first, the temperature was raised from room temperature to 120℃ at 5℃ / min and held for 1 h, then the temperature was raised to 300℃ at 2℃ / min and held for 2 h, and then naturally cooled to room temperature to obtain PI / Al2O3 composite fiber.

[0048] The preparation method of PI / Al2O3 composite fiber has been disclosed in the prior art. The specific method used to prepare it does not affect the performance of the friction material of the present invention, nor is it the core improvement of the present invention. Therefore, those skilled in the art can use other existing preparation processes besides the above-mentioned method to prepare PI / Al2O3 composite fiber, which will not be described in detail in the present invention.

[0049] ③ 8~15wt% friction-reducing filler: including 3~5% polyketone, 3~5% Ti4MoSiB2 and 2~4% flake graphite.

[0050] The preferred mass ratio of polyketone to Ti4MoSiB2 is 1:1, and the preferred mass ratio of PI / Al2O3 composite fiber to the total mass of polyketone and Ti4MoSiB2 is 1~2:6~8. Under this dosage relationship, the synergistic effect of the multi-components can reach the best level.

[0051] ④ 8~12wt% adhesive: including 5~10% perfluoroether rubber and 2~4% boron lithium modified phenolic resin.

[0052] ⑤ 0.5~2wt% compounding agent: including 0.5~1.5% of 4,4'-(hexafluoroisopropylidene) bisphenol (abbreviated as bisphenol AF) and 0.1~0.5% butoxylated phenolic resin (accelerator BPP).

[0053] The present invention proposes a method for preparing a friction material for a smooth and quiet electromagnetic brake, comprising the following steps:

[0054] (1) Weigh out polyketone, Ti4MoSiB2 and PI / Al2O3 composite fiber according to the specified amount; mix polyketone and Ti4MoSiB2 and add 0.3~0.5% of silane coupling agent of the total mass of the two, place in a high-speed mixer and stir at 1000-1500rpm for 15-20min to form Ti4MoSiB2-polyketone predispersant; then mix Ti4MoSiB2-polyketone predispersant with PI / Al2O3 composite fiber and put it into an internal mixer, and internally mix at the highest internal mixing temperature of 50-70℃ for 25-30min. The PI / Al2O3 composite fiber is prevented from breaking through by gentle internal mixing, and the interfacial bonding between the predispersant and the fiber is promoted to obtain the predispersant.

[0055] (2) Weigh the remaining raw materials according to the amount, and put them into the internal mixer together with the pre-dispersed material. At the same time, add 0.5~1% of ethanol of the total mass of the raw materials. Mix at the highest mixing temperature of 50-80℃ for 10-30 minutes to obtain the internal mixed material. Crush the internal mixed material and sieve it to obtain the internal mixed granules with appropriate particle size.

[0056] (3) Place the granulated material in a cold press mold at 50-60℃ and perform 3-5 venting processes. Each venting process includes 8s pressing and 3s venting. Then, cold press at 50-60MPa for 20-30s to obtain a cold billet.

[0057] (4) Place the cold blank in a hot press mold at 150±5℃ and press it at 40-50MPa. The hot pressing holding time is 80-100s / mm to obtain the friction plate.

[0058] (5) Place the friction plate in a heat treatment furnace, heat it, perform heat treatment, and remove it after cooling.

[0059] The specific heating process of heat treatment is as follows:

[0060] 5.1 First, heat the sample from room temperature to 120±5℃ for 50-60 minutes, and then keep it at that temperature for 1-2 hours;

[0061] 5.2 After another 30-60 minutes, heat to 180±5℃ and hold for 0.5-1.5 hours;

[0062] 5.3 After 30-60 minutes, heat to 220±5℃ and hold for 6-8 hours;

[0063] 5.4 Finally, after 40-50 minutes, cool down to 180±5℃, hold for 1-2 hours, and then cool with the furnace to 50℃ or below before removing.

[0064] (6) The friction pads after heat treatment are surface ground to obtain friction material for electromagnetic brakes made of granular material.

[0065] Example 1

[0066] Step 1: By weight, take 12 parts mineral fiber, 10 parts nano montmorillonite, 8 parts perfluoroether rubber, 8 parts magnesium oxide whiskers, 8 parts needle-shaped wollastonite, 6 parts calcium fluoride, 6 parts cashew shell oil friction powder, 5 parts cryolite, 4 parts nano alumina, 3.5 parts Ti4MoSiB2, 3 parts boron-lithium modified phenolic resin (provided by Jilin Weiqi Company), 3.5 parts polyketone, 3 parts flake graphite, 2 parts carbon nanotubes, 2 parts nano silicon carbide, 1 part PI / Al2O3 composite fiber, 1 part bisphenol AF, 0.6 parts carbon black, and 0.2 parts accelerator BPP as raw materials for later use.

[0067] Step 2: First, mix polyketone with Ti4MoSiB2, add about 0.028 parts by weight of silane coupling agent KH550, place in a high-speed mixer, stir at 1250 rpm for 18 min, then add PI / Al2O3 composite fiber and mix, and put into an internal mixer, and internally mix at the highest mixing temperature of 65℃ for 28 min to obtain pre-dispersed material.

[0068] Step 3: Put the above pre-dispersed material and the remaining raw materials into a mixer, add 0.7 parts by mass of analytical grade industrial alcohol, and mix at the highest mixing temperature of 65°C for 20 minutes to obtain a mixed material; crush the mixed material, sieve it, and screen out particles with a particle size of 1~2mm to obtain mixed granules.

[0069] Step 4: Place the granulated material into a 55℃ cold press mold, first press for 8 seconds and then vent for 3 seconds to perform 3 cycles of venting, and then hold the cold press at 55MPa for 25 seconds to obtain a cold billet.

[0070] Step 5: Place the cold blank in a hot press mold at 150℃ and hold it at 45MPa for 90s / mm to obtain the friction plate.

[0071] Step 6: Place the friction plate in a heat treatment furnace. First, heat it from room temperature to about 120°C for 55 minutes and hold it at that temperature for 1.5 hours. Then, heat it to about 180°C for 45 minutes and hold it at that temperature for 1 hour. After that, heat it to about 220°C for 45 minutes and hold it at that temperature for 7 hours. Finally, cool it down to about 180°C for 45 minutes and hold it at that temperature for 1.5 hours. Then, let it cool down with the furnace to below 50°C before removing it.

[0072] Step 7: Grind the surface of the heat-treated friction pad to obtain friction material.

[0073] Example 2

[0074] The difference between this embodiment and Embodiment 1 is that the raw material composition is different.

[0075] By weight, the raw materials in this embodiment include: 15 parts mineral fiber, 6 parts nano montmorillonite, 6 parts perfluoroether rubber, 10 parts magnesium oxide whiskers, 10 parts needle-like wollastonite, 6 parts calcium fluoride, 8 parts cashew nutshell oil friction powder, 6 parts cryolite, 5 parts nano alumina, 3 parts Ti4MoSiB2, 4 parts boron-lithium modified phenolic resin, 4 parts polyketone, 2 parts flake graphite, 1 part carbon nanotubes, 3 parts nano silicon carbide, 1.5 parts PI / Al2O3 composite fiber, 0.8 parts bisphenol AF, 0.5 parts carbon black, and 0.1 parts accelerator BPP.

[0076] Example 3

[0077] The difference between this embodiment and Embodiment 1 is that the raw material composition is different.

[0078] By weight, the raw materials in this embodiment include: 10 parts mineral fiber, 7 parts nano montmorillonite, 9 parts perfluoroether rubber, 6 parts magnesium oxide whiskers, 12 parts needle-like wollastonite, 5 parts calcium fluoride, 9 parts cashew nutshell oil friction powder, 7 parts cryolite, 6 parts nano alumina, 2 parts Ti4MoSiB2, 2 parts boron-lithium modified phenolic resin, 5 parts polyketone, 4 parts flake graphite, 1.5 parts carbon nanotubes, 1 part nano silicon carbide, 2 parts PI / Al2O3 composite fiber, 1.2 parts bisphenol AF, 0.8 parts carbon black, and 0.3 parts accelerator BPP.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 1 is that the raw materials do not include PI / Al2O3 composite fibers.

[0081] By weight, the raw materials in this comparative example include: 12 parts mineral fiber, 10 parts nano montmorillonite, 8 parts perfluoroether rubber, 8 parts magnesium oxide whiskers, 8 parts needle-like wollastonite, 6 parts calcium fluoride, 6 parts cashew nutshell oil friction powder, 5 parts cryolite, 4 parts nano alumina, 4 parts Ti4MoSiB2, 3 parts boron-lithium modified phenolic resin, 3 parts polyketone, 3 parts flake graphite, 2 parts carbon nanotubes, 2 parts nano silicon carbide, 1 part bisphenol AF, 0.6 parts carbon black, and 0.2 parts accelerator BPP.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 2 is that the raw materials do not include carbon nanotubes.

[0084] By weight, the raw materials in this comparative example include: 15 parts mineral fiber, 6 parts nano montmorillonite, 6 parts perfluoroether rubber, 10 parts magnesium oxide whiskers, 10 parts needle-like wollastonite, 6 parts calcium fluoride, 8 parts cashew nutshell oil friction powder, 6 parts cryolite, 5 parts nano alumina, 3 parts Ti4MoSiB2, 4 parts boron-lithium modified phenolic resin, 4 parts polyketone, 2 parts flake graphite, 3 parts nano silicon carbide, 1.5 parts PI / Al2O3 composite fiber, 0.8 parts bisphenol AF, 0.5 parts carbon black, and 0.1 parts accelerator BPP.

[0085] Comparative Example 3

[0086] The difference between this comparative example and Example 3 is that the raw materials do not include magnesium oxide whiskers.

[0087] By weight, the raw materials in this comparative example include: 10 parts mineral fiber, 7 parts nano montmorillonite, 9 parts perfluoroether rubber, 12 parts needle-like wollastonite, 5 parts calcium fluoride, 9 parts cashew nutshell oil friction powder, 7 parts cryolite, 6 parts nano alumina, 2 parts Ti4MoSiB2, 2 parts boron-lithium modified phenolic resin, 5 parts polyketone, 4 parts flake graphite, 1.5 parts carbon nanotubes, 1 part nano silicon carbide, 2 parts PI / Al2O3 composite fiber, 1.2 parts bisphenol AF, 0.8 parts carbon black, and 0.3 parts accelerator BPP.

[0088] Comparative Example 4

[0089] The difference between this comparative example and Example 1 is that the raw materials do not include polyketone.

[0090] By weight, the raw materials in this comparative example include: 12 parts mineral fiber, 10 parts nano montmorillonite, 8 parts perfluoroether rubber, 8 parts magnesium oxide whiskers, 8 parts needle-shaped wollastonite, 6 parts calcium fluoride, 6 parts cashew nutshell oil friction powder, 5 parts cryolite, 4 parts nano alumina, 4 parts Ti4MoSiB2, 3 parts boron-lithium modified phenolic resin, 3 parts flake graphite, 2 parts carbon nanotubes, 2 parts nano silicon carbide, 1 part PI / Al2O3 composite fiber, 1 part bisphenol AF, 0.6 parts carbon black, and 0.2 parts accelerator BPP.

[0091] Comparative Example 5

[0092] The difference between this comparative example and Example 2 is that Ti4MoSiB2 is not included in the raw materials.

[0093] By weight, the raw materials in this comparative example include: 12 parts mineral fiber, 10 parts nano montmorillonite, 8 parts perfluoroether rubber, 8 parts magnesium oxide whiskers, 8 parts needle-shaped wollastonite, 6 parts calcium fluoride, 6 parts cashew nutshell oil friction powder, 5 parts cryolite, 4 parts nano alumina, 3 parts boron-lithium modified phenolic resin, 3 parts polyketone, 3 parts flake graphite, 2 parts carbon nanotubes, 2 parts nano silicon carbide, 1 part PI / Al2O3 composite fiber, 1 part bisphenol AF, 0.6 parts carbon black, and 0.2 parts accelerator BPP.

[0094] Comparative Example 6

[0095] The difference between this comparative example and Example 3 is that the raw materials do not include nano-clay.

[0096] By mass, the raw materials in this comparative example include: 12 parts mineral fiber, 8 parts perfluoroether rubber, 8 parts magnesium oxide whiskers, 8 parts needle-shaped wollastonite, 6 parts calcium fluoride, 6 parts cashew nutshell oil friction powder, 5 parts cryolite, 4 parts nano alumina, 4 parts Ti4MoSiB2, 3 parts boron-lithium modified phenolic resin, 3 parts polyketone, 3 parts flake graphite, 2 parts carbon nanotubes, 2 parts nano silicon carbide, 1 part PI / Al2O3 composite fiber, 1 part bisphenol AF, 0.6 parts carbon black, and 0.2 parts accelerator BPP.

[0097] Comparative Example 7

[0098] The difference between this comparative example and Example 1 is that 2123 phenolic resin is used instead of boron-lithium modified phenolic resin.

[0099] Comparative Example 8

[0100] The difference between this comparative example and Example 1 is that nitrile rubber is used instead of perfluoroether rubber.

[0101] Test case

[0102] Samples: Examples 1-3, Comparative Examples 1-8

[0103] The specific raw material formulations for the samples of Examples 1-3 and Comparative Examples 1-6 are shown in Table 1 below:

[0104] Table 1. Raw material composition and content of different samples

[0105]

[0106] According to the test methods in GB / T 5764-2023 "Clutch Face Plates for Automobiles" and GB / T 33835-2017 "Test Method for Impact Strength of Friction Materials", the friction properties of the above samples were tested respectively, and the test results are summarized in Table 2 below:

[0107] Table 2. Test results of friction properties of different samples

[0108]

[0109] The above samples were assembled into electromagnetic brakes, with a rated torque of 3.2 N·m. Then, according to the test methods in GB / T34114-2017 "General Technical Conditions for Electromagnetic Brakes for Electric Motors", the electromagnetic brakes assembled from different samples were subjected to a grinding test. The motor speed was controlled at 1200 rpm, with grinding for 1 second and idling for 1 second constituting one grinding cycle. Each sample underwent two tests. The test results are summarized in Table 3 below.

[0110] Table 3. Grinding test results of electromagnetic brakes assembled with different samples.

[0111]

[0112] The above experiments and test results show that:

[0113] (1) The friction materials prepared in Examples 1-3, in the friction performance test, while maintaining a similar coefficient of friction, have significantly lower wear rate and noise than the friction materials in Comparative Examples 1 to 8, and significantly higher impact strength. This shows that the friction material and its preparation method proposed in this invention can solve and improve the problems of instability and high noise caused by friction damage in existing friction materials while maintaining the coefficient of friction.

[0114] (2) By assembling different samples from Examples 1-3 and Comparative Examples 1-8 into electromagnetic brakes, multiple tests showed that the electromagnetic brakes in Examples 1-3 exhibited more stable static torque under different grinding periods, demonstrating a more precise transmission of force and torque. This indicates that the friction material and its preparation method proposed in this invention can further enhance the functionality of existing electromagnetic brake stacks, meeting the performance requirements for safety, efficiency, and reliability in higher-end assembly applications.

[0115] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A friction material for a smooth and quiet electromagnetic brake, characterized by, The friction material comprises 40-50 wt% of the friction-enhancing filler, 15-30 wt% of the reinforcing material, 8-12 wt% of the adhesive, 8-15 wt% of the friction-reducing filler, and 0.5-2 wt% of the compounding agent; The reinforcing material comprises 10-15 wt% of the mineral fiber, 5-10 wt% of the magnesium oxide whisker, 1-3 wt% of the carbon nanotube, and 1-2 wt% of the PI / Al2O3 composite fiber; the friction-reducing filler comprises 3-5 wt% of the polyketone, 3-5 wt% of the Ti4MoSiB2, and 2-4 wt% of the flake graphite; the friction-enhancing filler comprises 8-12 wt% of the acicular wollastonite, 6-10 wt% of the cashew shell oil friction powder, 5-10 wt% of the nano-clay, 5-8 wt% of the cryolite, 5-8 wt% of the calcium fluoride, 3-6 wt% of the nano-alumina, 1-3 wt% of the nano-silicon carbide, and 0.5-1 wt% of the carbon black; and the adhesive comprises 5-10 wt% of the perfluoroether rubber and 2-4 wt% of the boron-lithium modified phenolic resin.

2. The friction material for use in a smooth and quiet electromagnetic brake according to claim 1, wherein The mass ratio of the polyketone to the Ti4MoSiB2 is 1:1, and the ratio of the PI / Al2O3 composite fiber to the total mass of the polyketone and the Ti4MoSiB2 is 1-2:6-8.

3. A method of producing the friction material for the electromagnetic brake which is smooth and quiet in braking as claimed in claim 1 or 2, characterized in that, The method comprises the following steps: S1, pre-dispersing: the polyketone, the Ti4MoSiB2, and the PI / Al2O3 composite fiber are weighed, the polyketone and the Ti4MoSiB2 are mixed with the silane coupling agent, and stirring and dispersion are performed at 1000-1500 rpm; then the PI / Al2O3 composite fiber is added and mixed, and the mixture is put into a banbury mixer, the maximum banburying temperature is 50-70℃, and banburying is performed for 25-30 min to obtain a pre-dispersed material; S2, mixing and banburying: the remaining raw materials are weighed, mixed with the pre-dispersed material, banbured, crushed, and sieved to obtain banbured granular material; S3, cold pressing: the banbured granular material is cold pressed at 50-60℃ to obtain a cold blank; S4, hot pressing: the cold blank is hot pressed at 150±5℃ to obtain a friction plate; S5, heat treatment: the friction plate is subjected to gradient heating, heat preservation, and then gradient cooling; S6, post-treatment: the friction plate after the heat treatment is subjected to surface grinding to obtain the friction material for the electromagnetic brake.

4. The method of claim 3, wherein the friction material is prepared by mixing the binder, the filler, the lubricant, the friction modifier, the metal fiber, and the metal powder, and then molding the mixture. In step S2, the maximum banburying temperature is 50-80℃, and the banburying time is 10-30 min.

5. The method of claim 3, wherein the friction material is prepared by mixing the binder, the filler, the lubricant, the friction modifier, the metal fiber, and the metal powder, and then molding the mixture. In step S3, the cold pressing pressure is 50-60 MPa, and the cold pressing pressure maintaining time is 20-30 s; In step S4, the hot pressing pressure is 40-50 MPa, and the hot pressing pressure maintaining time is 80-100 s / mm.

6. The method of claim 3, wherein the friction material is prepared by mixing the binder, the filler, the lubricant, the friction modifier, the metal fiber, the metal powder, and the metal oxide, and then molding the mixture. In step S5, the specific process of the heat treatment is as follows: S5.1, the friction plate is placed in a heating furnace, heated from room temperature to 120±5℃ for 50-60 min, and then heat preserved for 1-2 h; S5.2, heated to 180±5℃ for 30-60 min, and then heat preserved for 0.5-1.5 h; S5.3, heated to 220±5℃ for 30-60 min, and then heat preserved for 6-8 h; S5.4, finally cooled to 180±5℃ for 40-50 min, heat preserved for 1-2 h, and then taken out after the furnace is cooled to 50℃ or below.

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