A shock absorber based on anti-settling magnetorheological fluid

Abstract

The present invention relates to the technical field of automobile shock absorbers, and more specifically to a shock absorber based on anti-settling magnetorheological fluid. The main technical solution is as follows: an outer cylinder and a floating piston; the floating piston is slidably mounted at the lower inner portion of the outer cylinder; the floating piston divides the interior of the outer cylinder into a working chamber and a gas chamber; the gas chamber is located at the lower portion of the outer cylinder and is filled with nitrogen; and the working chamber is filled with anti-settling magnetorheological fluid; a piston assembly is slidably mounted within the outer cylinder, dividing the working chamber within the outer cylinder into an upper chamber and a lower chamber. The present invention significantly improves the performance of the magnetorheological fluid through innovative gradient coating structure design and interface control technology. Hollow iron powder is used as the core, and an Fe3O4 transition layer and a polyethylene coating layer are sequentially constructed on its surface to form a unique three-layer composite structure.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile shock absorbers, and is particularly suitable for scenarios such as automobile shock absorbers and precision polishing that have high requirements for the stability of magnetorheological fluids. Background Art

[0002] Vibration reduction technologies can be categorized into three main types: active, passive, and hybrid, depending on whether external energy input is required. Passive damping technologies primarily include cylinder damping (e.g., oil and air cylinders), rigid elastic damping (e.g., coil springs and reeds), and flexible elastomer damping (e.g., silicone rubber). However, passive damping technologies suffer from significant shortcomings in control performance, primarily manifested in poor controllability and low control accuracy. Actively adjusting the stiffness of a material using a magnetic field enables precise control of its damping properties. These intelligent materials with magnetically controlled properties are known as magnetorheological materials.

[0003] Magnetorheological fluid (MRF) is a smart material composed of micron- or nanometer-sized magnetic particles dispersed in a carrier fluid. Its rheological properties can be rapidly and reversibly tuned by an applied magnetic field. This property holds great promise for applications in automotive suspension systems, precision polishing, dampers, and medical devices. However, long-term stability issues, particularly magnetic particle sedimentation and interfacial failure, severely limit its industrial application. Summary of the Invention

[0004] In order to overcome the difficulties of sedimentation and interface peeling of magnetic particles in magnetorheological fluid while maintaining the disadvantage of high magnetic responsiveness, the technical problem to be solved is to provide a shock absorber based on anti-sedimentation magnetorheological fluid.

[0005] The technical solution is: a shock absorber based on anti-settling magnetorheological fluid, including an outer cylinder, a floating piston, a piston assembly, an excitation coil, an acceleration sensor and a return spring. The floating piston is slidably installed at the lower inner side of the outer cylinder. The floating piston divides the interior of the outer cylinder into a working chamber and a gas chamber. The gas chamber is located at the lower part of the outer cylinder. The gas chamber is filled with nitrogen. The working chamber is filled with anti-settling magnetorheological fluid. The piston assembly is slidably arranged in the outer cylinder. The piston assembly divides the working chamber in the outer cylinder into an upper chamber and a lower chamber. The excitation coil is arranged around the outside of the outer cylinder or integrated in the piston assembly to generate a controllable magnetic field. The damping channel is opened in the piston assembly. The damping channel is spiral, straight or broken line-shaped. The acceleration sensor is arranged at the end of the outer cylinder for real-time monitoring of vibration signals. The return spring is arranged between the outer cylinder and the piston assembly. The return spring is used to provide elastic buffering force and cooperates with the floating piston to form an anti-collision buffer mechanism.

[0006] Furthermore, the piston assembly includes a coaxially arranged piston rod, a damping piston head, and a sealing ring. The damping piston head is hollow, and an annular groove is provided on the outer periphery of the damping piston head. An excitation coil is embedded in the groove. The sealing ring is installed on the outside of the annular groove on the outer periphery of the damping piston head to isolate the excitation coil from contact with the anti-sedimentation magnetorheological fluid. The damping channel extends in a spiral, straight or broken line shape in the damping piston head, and a magnetic conductive material is provided between the excitation coil and the damping channel to enhance the magnetic field strength in the damping channel. The excitation coil is electrically connected to an external controller through a hollow piston rod. The piston rod is used to transmit a control current to adjust the magnetic field strength generated by the excitation coil. The gap width of the damping channel is 0.2-1.0mm, and the channel surface is coated with a tungsten carbide wear-resistant layer. An axial groove is provided at the working chamber position on the inner wall of the outer cylinder, and the axial groove depth is 0.5-2mm to enhance the turbulent effect of the anti-sedimentation magnetorheological fluid.

[0007] Furthermore, the preparation method of the anti-settling magnetorheological fluid includes the following steps: magnetic particle pretreatment: drying the hollow iron powder; additive mixing: adding graphite and anti-wear agent, thickener, antioxidant, pour point depressant, stabilizer, and defoaming agent to hydraulic oil to dissolve and form a uniform mixed liquid; initial stirring and dispersion: slowly adding the dried hollow iron powder to the mixed liquid, stirring, and preliminarily dispersing the magnetic particles; secondary stirring and homogenization: pouring the magnetic particles and the mixed liquid into a high-speed stirrer, and stirring at a high speed of 20,000-30,000 r / min to obtain the anti-settling magnetorheological fluid.

[0008] Furthermore, the hollow iron powder is a composite particle with a polyethylene layer coated on the surface of the hollow iron powder, and its preparation method includes: mixing the dried hollow iron powder with molecular weight polyethylene; heating to 110-150°C under nitrogen protection and melting and coating; after cooling, grading through a 200-400 mesh sieve to form a coating layer.

[0009] Furthermore, the composite particles of the hollow iron powder are coated with a polyethylene layer, and a Fe3O4 transition layer is further included between the hollow iron powder and the polyethylene layer to form a three-layer structure composite particle; the preparation method of the Fe3O4 transition layer is as follows:

[0010] The hollow iron powder is treated in Ar / O2 plasma to generate nano-scale oxide protrusions on the surface and then dried;

[0011] The treated hollow iron powder reacts with FeCl3 solution to form a Fe3O4 transition layer on the surface.

[0012] Furthermore, the preparation method of the three-layer structure composite particles is as follows: hollow iron powder is treated in Ar / O2 plasma to generate nano-scale oxide protrusions on the surface, and then dried; the dried hollow iron powder is reacted with FeCl3 solution to generate an Fe3O4 transition layer on the surface; a branched polyethylene wax containing 1-3wt% maleic anhydride grafted polyethylene is mixed with the hollow iron powder and melt-coated; after cooling, the mixture is graded through a 200-400 mesh sieve to form a coating layer.

[0013] Furthermore, in the three-layer composite particles, the thickness ratio of the Fe3O4 transition layer and the coating layer is calculated by the following formula:

[0014] Among them, E Fe is the elastic modulus of iron, in GPa; E PE is the elastic modulus of polyethylene, in GPa; α Fe is the thermal expansion coefficient of iron, in units of 1×10 -6 K -1 ; α Fe3O4 is the thermal expansion coefficient of Fe3O4, the unit is 1×10 -6 K -1 ; α PE is the thermal expansion coefficient of polyethylene, in units of 1×10 -6 K -1 ; r0=100 nm, is the characteristic length; r is the current particle size of the hollow iron powder in nm;

[0015] is the surface energy of Fe3O4, the unit is J / m 2 ;

[0016] is the surface energy of PE, the unit is J / m 2 ;

[0017] is the surface energy of Fe, in J / m 2 ;

[0018] and =0.5 ; =1.2 .

[0019] Furthermore, the particle size of the hollow iron powder is 300-600 nm.

[0020] Furthermore, the kinematic viscosity of the hydraulic oil at 20° C. is 20-60 mPa·s.

[0021] Furthermore, the pour point depressant is alkyl naphthalene.

[0022] Furthermore, the anti-wear agent is chlorinated paraffin.

[0023] Furthermore, the thickener is a high molecular weight polyether.

[0024] Furthermore, the antioxidant is a dialkyl dithiophosphate.

[0025] Furthermore, the defoaming agent is dimethyl silicone oil.

[0026] Furthermore, the amount of graphite added is 1%-3% of the mass of the hydraulic oil, the amount of antioxidant added is 1%-2% of the hydraulic oil, the amount of pour point depressant added is 0.5%-1% of the hydraulic oil, the amount of thickener added is 1%-2.5% of the mass of the hydraulic oil, the amount of stabilizer added is 1%-2% of the hydraulic oil, the amount of anti-wear agent added is 1%-3% of the mass of the hydraulic oil, and the amount of defoaming agent added is 1% of the mass of the hydraulic oil.

[0027] Furthermore, the drying temperature is 160-180°C.

[0028] Furthermore, the rotation speed of the initial stirring and dispersing is 5000-10000 r / min.

[0029] Furthermore, the power of the Ar / O2 plasma is 100W, and the gas ratio is 4:1.

[0030] Furthermore, the nano-scale oxide protrusions have a Ra value of 50-100 nm.

[0031] Furthermore, the FeCl3 solution is 0.1 mol / L.

[0032] Beneficial effects: The present invention significantly improves the performance of magnetorheological fluid through innovative gradient coating structure design and interface control technology. Hollow iron powder is used as the core, and a Fe3O4 transition layer and a polyethylene coating layer are sequentially constructed on its surface to form a unique three-layer composite structure. This design effectively alleviates the difference in thermal expansion coefficient between the iron core and the polymer coating through the transition layer, greatly improving the interface bonding strength. At the same time, the precisely controlled coating layer thickness ensures efficient penetration of the magnetic field, giving the material both excellent magnetic response performance and stability. The polyethylene outer layer gives the particle surface super-oleophobic properties, effectively inhibiting particle agglomeration and sedimentation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention.

[0034] Figure 2 It is a partial cross-sectional structural schematic diagram of the present invention.

[0035] Figure 3 It is a schematic diagram of a partial explosion structure of the present invention.

[0036] Markings in the figure are: 1-outer cylinder, 2-piston rod, 3-damping piston head, 4-floating piston, 5-acceleration sensor, 6-damping channel, 7-excitation coil, 8-sealing ring, 9-axial groove, 10-return spring. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but this does not limit the present invention.

[0038] This embodiment provides a shock absorber based on anti-settling magnetorheological fluid, comprising an outer cylinder 1, a floating piston 4, a piston assembly, an excitation coil 7, an acceleration sensor 5, and a return spring 10. The floating piston 4 is slidably mounted on the lower inner portion of the outer cylinder 1. The floating piston 4 divides the interior of the outer cylinder 1 into a working chamber and a gas chamber. The gas chamber is located at the lower portion of the outer cylinder 1 and is filled with nitrogen. The working chamber is filled with anti-settling magnetorheological fluid. The piston assembly is slidably mounted within the outer cylinder 1, dividing the working chamber within the outer cylinder 1 into an upper chamber and a lower chamber. The excitation coil 7 is disposed around the outer side of the outer cylinder 1 or integrated within the piston assembly to generate a controllable magnetic field. A damping channel 6 is provided within the piston assembly and has a spiral, linear, or zigzag shape. The acceleration sensor 5 is disposed at the end of the outer cylinder 1 to monitor vibration signals in real time. The return spring 10 is disposed between the outer cylinder 1 and the piston assembly. The return spring 10 is configured to provide elastic buffering force and, in conjunction with the floating piston 4, forms an anti-collision buffering mechanism.

[0039] The piston assembly includes a coaxially arranged piston rod 2, a damping piston head 3, and a sealing ring 8. The damping piston head 3 is hollow, and an annular groove is provided on the outer periphery of the damping piston head 3. An excitation coil 7 is embedded in the groove. The sealing ring 8 is installed on the outside of the annular groove on the outer periphery of the damping piston head 3 to isolate the excitation coil 7 from contact with the anti-sedimentation magnetorheological fluid. The damping channel 6 extends in a spiral, straight or broken line shape in the damping piston head 3, and a magnetic conductive material is provided between the excitation coil 7 and the damping channel 6 to enhance the magnetic field strength in the damping channel 6. The excitation coil 7 is electrically connected to the external controller through the hollow piston rod 2. The piston rod 2 is used to transmit a control current to adjust the magnetic field strength generated by the excitation coil 7. The gap width of the damping channel 6 is 0.2~1.0mm, and the channel surface is coated with a tungsten carbide wear-resistant layer. An axial groove 9 is provided at the working chamber position on the inner wall of the outer cylinder 1. The depth of the axial groove 9 is 0.5-2mm to enhance the turbulent effect of the anti-sedimentation magnetorheological fluid.

[0040] In some preferred embodiments, the method for preparing the anti-settling magnetorheological fluid comprises the following steps:

[0041] Magnetic particle pretreatment: drying the hollow iron powder;

[0042] Additive mixing: add graphite and anti-wear agent, thickener, antioxidant, pour point depressant, stabilizer, defoamer into the hydraulic oil and dissolve them to form a uniform mixture;

[0043] Initial stirring and dispersion: slowly add the dried hollow iron powder into the mixture and stir to initially disperse the magnetic particles;

[0044] After secondary stirring and homogenization, the magnetic particles and the mixed solution are poured into a high-speed stirrer and stirred at a high speed of 20,000-30,000 r / min to obtain the anti-sedimentation magnetorheological fluid.

[0045] The prepared anti-settling magnetorheological fluid is injected into the damping working chamber of the magnetorheological shock absorber to form a controllable damping medium.

[0046] It can be understood that in this specific embodiment, the hollow iron powder is first dried and pretreated to ensure the surface activity of the particles; then a variety of functional additives (graphite, anti-wear agents, etc.) are evenly dispersed in the hydraulic oil to form a stable mixture; through a step-by-step stirring process, the magnetic particles are first initially dispersed under mild conditions, and then a high-speed homogenization stirring of 20,000-30,000 r / min is used to achieve nano-scale uniform dispersion of the particles. This process ensures the full dispersion of the magnetic particles through physical and chemical synergy, and avoids particle breakage caused by high-speed shearing. The magnetorheological fluid finally obtained has excellent anti-sedimentation and long-term storage stability, while maintaining a good magnetorheological effect.

[0047] In some preferred embodiments, the hollow iron powder is a composite particle with a polyethylene layer coated on the surface of the hollow iron powder, and the preparation method thereof includes:

[0048] Mixing the dried hollow iron powder with molecular weight polyethylene;

[0049] Heat to 110-150℃ under nitrogen protection for melt coating;

[0050] After cooling, the mixture is graded through a 200-400 mesh sieve to form a coating layer.

[0051] It can be understood that in this specific embodiment, a composite particle structure of hollow iron powder coated with polyethylene is used. The preparation process uses a melt coating process under nitrogen protection to uniformly coat the polyethylene on the surface of the iron powder in the temperature range of 110-150°C, and forms a complete and dense coating layer after sieving. On the one hand, the polyethylene coating layer effectively weakens the van der Waals interaction between magnetic particles by reducing the surface energy of the particles, thereby inhibiting particle agglomeration; on the other hand, the good compatibility of polyethylene with hydraulic oil improves the wettability of the particles in the carrier liquid, forming a stable suspension system. In particular, the steric hindrance effect formed by the polyethylene coating on the surface of the particles can significantly hinder the Brownian motion aggregation and gravitational sedimentation of the particles, thereby enabling the magnetorheological fluid to obtain excellent anti-sedimentation properties and achieve long-term storage stability. This coating structure fundamentally solves the technical problem of easy sedimentation and stratification of traditional magnetorheological fluids while maintaining the magnetic response properties of the material.

[0052] In some preferred embodiments, the composite particles are formed by coating the surface of the hollow iron powder with a polyethylene layer, and further comprising an Fe3O4 transition layer between the hollow iron powder and the polyethylene layer, forming a three-layer composite particle; the preparation method of the Fe3O4 transition layer is as follows:

[0053] The hollow iron powder is treated in Ar / O2 plasma to generate nano-scale oxide protrusions on the surface and then dried;

[0054] The treated hollow iron powder reacts with FeCl3 solution to form a Fe3O4 transition layer on the surface.

[0055] It is understandable that the three-layer coating structure design (Fe-Fe3O4-PE) constructs a nano-scale Fe3O4 transition layer on the surface of the hollow iron powder through plasma treatment and chemical oxidation, and then covers it with a polyethylene outer layer. The core advantages of this structure are: the Fe3O4 transition layer acts as a "molecular bridge", simultaneously connecting the iron core and the PE layer through chemical bonds, significantly improving the interfacial bonding strength; the nano-protrusions produced by the plasma treatment increase the specific surface area, making the subsequent Fe3O4 layer growth more uniform and dense. This gradient design enables the particles to maintain ultra-low adhesion (≤8nN) in the carrier liquid, while the PE outer layer provides steric hindrance and oleophobic effects (contact angle ≥120°). The triple synergistic effect enables the magnetorheological fluid to have both super strong anti-sedimentation properties (500h sedimentation rate <5%) and excellent magnetic response performance (yield stress ≥50kPa).

[0056] In some preferred embodiments, the preparation method of the three-layer structure composite particles is as follows:

[0057] The hollow iron powder is treated in Ar / O2 plasma to generate nano-scale oxide protrusions on the surface and then dried;

[0058] The dried hollow iron powder reacts with FeCl3 solution to form a Fe3O4 transition layer on the surface;

[0059] Mixing branched polyethylene wax containing 1-3 wt% maleic anhydride grafted polyethylene with hollow iron powder and melt coating;

[0060] After cooling, the mixture is graded through a 200-400 mesh sieve to form a coating layer.

[0061] It is understandable that nano-scale oxide protrusions are constructed on the surface of the hollow iron powder through Ar / O2 plasma treatment. This micro-roughening treatment not only increases the specific surface area, but also provides an ideal nucleation site for the subsequent growth of the Fe3O4 layer; the Fe3O4 transition layer subsequently generated by reaction with FeCl3 solution has dual functions. Its spinel structure can not only form a strong Fe-O-Fe bond with the iron core, but also undergo esterification reaction with maleic anhydride grafted polyethylene (MAH-g-PE) through surface hydroxyl groups to achieve molecular-level interface coupling; branched polyethylene wax (containing 1-3wt% MAH-g-PE) is specially selected for melt coating. Its branched structure can enhance the flexibility of the coating layer, while the maleic anhydride group produces chemical bonding with the Fe3O4 surface. The final PE coating layer has excellent integrity and bonding strength. This gradient structural design enables the particles to exhibit ultra-low interfacial energy (γ<0.5J / m 2 ), the monodisperse particle system obtained after sieve classification can achieve anti-sedimentation, improve shear yield strength and maintain stable performance in a wide temperature range of -40 to 120°C, completely solving the technical problem of easy failure of traditional magnetorheological fluid interface.

[0062] In some preferred embodiments, in the three-layer composite particles, the thickness ratio of the Fe3O4 transition layer to the coating layer is calculated by the following formula:

[0063] ;

[0064] in,

[0065] E Fe is the elastic modulus of iron, in GPa;

[0066] E PE is the elastic modulus of polyethylene, in GPa;

[0067] α Fe is the thermal expansion coefficient of iron, in units of 1×10 -6 K -1 ;

[0068] α Fe3O4 is the thermal expansion coefficient of Fe3O4, the unit is 1×10 -6 K -1 ;

[0069] α PE is the thermal expansion coefficient of polyethylene, in units of 1×10 -6 K -1 ;

[0070] r0=100 nm, characteristic length;

[0071] r is the current particle size of the hollow iron powder in nm;

[0072] is the surface energy of Fe3O4, the unit is J / m 2 ;

[0073] is the surface energy of PE, the unit is J / m 2 ;

[0074] is the surface energy of Fe, in J / m 2 ;

[0075] and =0.5 ; =1.2 .

[0076] It is understandable that the above thickness ratio calculation formula is based on the principle of multi-physics field coupling, and the optimal design of the coating structure is achieved by quantifying three key interactions. The molecular term E in the formula is PE (α Fe3O4 -α PE ) / E Fe (α Fe -α Fe3O4 ) reflects the thermodynamic matching mechanism: using the difference in thermal expansion coefficient between polyethylene and Fe3O4 and the difference between iron and Fe3O4, combined with the elastic modulus ratio of the two, the thickness ratio base required for thermal stress balance is accurately calculated, and the correction term Then the synergistic effect of interface energy and particle size is introduced: γ Fe3O4 / γ PE =0.5 represents the interface bonding strength between the transition layer and PE, γ Fe / γ Fe3O4 =1.2 reflects the interface stability between the iron core and the transition layer, and the term r0 / r enables adaptive particle size adjustment (a characteristic length of 100 nm ensures nanoscale applicability). This formula establishes a ternary mathematical model of thermal expansion, interfacial energy, and particle size. By manipulating the value of η, interfacial thermal stress can be reduced while maintaining magnetic field penetration efficiency. This guides the precise preparation of the Fe3O4 and PE layers during the process, ensuring that the coating integrity of the magnetorheological fluid remains at 92% after 100,000 shear cycles.

[0077] In some preferred embodiments, the particle size of the hollow iron powder is 300-600 nm.

[0078] In some preferred embodiments, the kinematic viscosity of the hydraulic oil at 20° C. is 20-60 mPa·s.

[0079] In some preferred embodiments, the pour point depressant is an alkyl naphthalene.

[0080] In some preferred embodiments, the antiwear agent is chlorinated paraffin.

[0081] In some preferred embodiments, the thickener is a high molecular weight polyether.

[0082] In some preferred embodiments, the antioxidant is a dialkyl dithiophosphate.

[0083] In some preferred embodiments, the defoaming agent is dimethicone.

[0084] In some preferred embodiments, the amount of graphite added is 1%-3% of the mass of the hydraulic oil, the amount of antioxidant added is 1%-2% of the mass of the hydraulic oil, the amount of pour point depressant added is 0.5%-1% of the mass of the hydraulic oil, the amount of thickener added is 1%-2.5% of the mass of the hydraulic oil, the amount of stabilizer added is 1%-2% of the mass of the hydraulic oil, the amount of anti-wear agent added is 1%-3% of the mass of the hydraulic oil, and the amount of defoaming agent added is 1% of the mass of the hydraulic oil.

[0085] In some preferred embodiments, the drying temperature is 160-180°C.

[0086] In some preferred embodiments, the rotation speed of the initial stirring and dispersing is 5000-10000 r / min.

[0087] In some preferred embodiments, the power of the Ar / O2 plasma is 100 W, and the gas ratio is 4:1.

[0088] In some preferred embodiments, the nano-scale oxide protrusions have a Ra of 50-100 nm.

[0089] It can be understood that in this specific embodiment, nano-scale oxide protrusions with Ra=50-100nm are constructed on the surface of the hollow iron powder by Ar / O2 plasma treatment. From the perspective of surface chemistry, the nano-protrusions increase the specific surface area by 3-5 times (confirmed by BET test), expose more active crystal planes (such as the {311} plane of Fe3O4), and provide high-density nucleation sites (≈105 sites / μm) for the subsequent transition layer growth. 2From a mechanical properties perspective, this roughness range optimizes the mechanical interlocking effect at the interface. A protrusion height of >50nm can break through the entanglement radius of the PE molecular chains (approximately 30nm), forming physical anchoring points. A limit of <100nm prevents interfacial crack propagation caused by stress concentration. Specifically in magnetorheological applications, this nanoprotrusion structure enables the Fe3O4 transition layer and the PE coating to form a "pinning-wetting" composite interface (the contact angle decreases from 105° for a smooth surface to 85°), achieving a triple stabilization mechanism of chemical bonding (Fe-OC=O), mechanical interlocking, and synergistic intermolecular forces. Ultimately, the particles maintain a high coating integrity after 104 shear cycles, a significant improvement over conventional smooth-surface particles.

[0090] In some preferred implementations, the FeCl3 solution is 0.1 mol / L.

[0091] This specific embodiment also provides an anti-settling magnetorheological fluid obtained by the above preparation method. Example 1

[0092] Reference Figure 1-Figure 3 A shock absorber based on anti-settling magnetorheological fluid is provided, comprising an outer cylinder 1, a floating piston 4, a piston assembly, an excitation coil 7, an acceleration sensor 5, and a return spring 10. The floating piston 4 is slidably mounted at the lower inner portion of the outer cylinder 1. The floating piston 4 divides the interior of the outer cylinder 1 into a working chamber and a gas chamber. The gas chamber is located at the lower portion of the outer cylinder 1 and is filled with nitrogen. The working chamber is filled with anti-settling magnetorheological fluid. The piston assembly is slidably disposed within the outer cylinder 1, dividing the working chamber within the outer cylinder 1 into an upper chamber and a lower chamber. The excitation coil 7 is disposed around the outer side of the outer cylinder 1 or integrated into the piston assembly for generating a controllable magnetic field. A damping channel 6 is provided within the piston assembly. The damping channel 6 is spiral, linear, or zigzag-shaped. The acceleration sensor 5 is disposed at the end of the outer cylinder 1 for real-time monitoring of vibration signals. The return spring 10 is disposed between the outer cylinder 1 and the piston assembly. The return spring 10 is configured to provide elastic buffering force and cooperates with the floating piston 4 to form an anti-collision buffering mechanism.

[0093] The piston assembly includes a coaxially arranged piston rod 2, a damping piston head 3, and a sealing ring 8. The damping piston head 3 is hollow, and an annular groove is provided on the outer periphery of the damping piston head 3, in which an excitation coil 7 is embedded. The sealing ring 8 is installed on the outside of the annular groove on the outer periphery of the damping piston head 3 to isolate the excitation coil 7 from contact with the anti-sedimentation magnetorheological fluid. The damping channel 6 extends in a spiral, straight or broken line shape in the damping piston head 3, and a magnetic conductive material is provided between the excitation coil 7 and the damping channel 6 to enhance the magnetic field strength in the damping channel 6. The excitation coil 7 is electrically connected to the external controller through the hollow piston rod 2. The piston rod 2 is used to transmit a control current to adjust the magnetic field strength generated by the excitation coil 7. The gap width of the damping channel 6 is 0.2-1.0 mm, and the surface of the channel is coated with a tungsten carbide wear-resistant layer. An axial groove 9 is provided at the working chamber position on the inner wall of the outer cylinder 1. The depth of the axial groove 9 is 0.5-2 mm to enhance the turbulent effect of the anti-sedimentation magnetorheological fluid.

[0094] The anti-settling magnetorheological fluid and its preparation method provided in this embodiment are as follows: The magnetorheological fluid formula provided in this embodiment is as follows:

[0095] Components Addition amount (wt%) Specific specifications / models No. 46 hydraulic oil Main body (balanced to 100%) Kinematic viscosity 45mPa·s (20℃) Hollow iron powder 20% <![CDATA[Particle size 500nm, density 2.3g / cm 3 > graphite 2% Scale-like, particle size 1-3 μm Chlorinated paraffin (antiwear agent) 2% Chlorine content 52% Polyether thickener 1.8% Molecular weight 5000 Dialkyl dithiophosphates (antioxidants) 1.5% <![CDATA[Model T203]]> Alkylated naphthalene (pour point depressant) 0.8% Freezing point -40℃ Dimethyl silicone oil (defoaming agent) 1% Viscosity 1000 cSt

[0096] The preparation method is as follows:

[0097] Step 1: Magnetic particle pretreatment

[0098] Take hollow iron powder with a particle size of 500nm (density 2.3g / cm 3 ) 100g, placed in a vacuum drying oven, drying parameters: 175℃, vacuum degree 10Pa, time 2.5h.

[0099] Step 2: Additive Mixing

[0100] Base fluid preparation: 500 mL of No. 46 hydraulic oil (kinematic viscosity 45 mPa·s@20°C);

[0101] Additive addition amount (based on the mass of hydraulic oil): graphite: 2wt% (10g), chlorinated paraffin (anti-wear agent): 2wt% (10g), polyether thickener (molecular weight 5000): 1.8wt% (9g), dialkyl dithiophosphate (antioxidant): 1.5wt% (7.5g), alkyl naphthalene (pour point depressant): 0.8wt% (4g), dimethyl silicone oil (defoaming agent): 1wt% (5g);

[0102] Mixing process: Stir at 8000 r / min for 30 min to obtain a mixed liquid.

[0103] Step 3: Magnetorheological fluid preparation

[0104] Initial dispersion: Add the pretreated hollow iron powder into the mixture at a rate of 5 g / min and stir at 9000 r / min for 40 min.

[0105] Secondary homogenization: transfer to a high-speed stirrer and stir at 25,000 r / min for 1 hour.

[0106] Among them, the thickness ratio of the Fe3O4 transition layer and the coating layer in the three-layer composite particles is calculated by the following formula:

[0107] ;

[0108] in,

[0109] E Fe is the elastic modulus of iron, in GPa;

[0110] E PE is the elastic modulus of polyethylene, in GPa;

[0111] α Fe is the thermal expansion coefficient of iron, in units of 1×10 -6 K -1 ;

[0112] α Fe3O4 is the thermal expansion coefficient of Fe3O4, the unit is 1×10 -6 K -1 ;

[0113] α PE is the thermal expansion coefficient of polyethylene, in units of 1×10 -6 K -1 ;

[0114] r0=100 nm, characteristic length;

[0115] r is the current particle size of the hollow iron powder, in nm;

[0116] is the surface energy of Fe3O4, the unit is J / m 2 ;

[0117] is the surface energy of PE, the unit is J / m 2 ;

[0118] is the surface energy of Fe, in J / m 2 ;

[0119] and =0.5 ; =1.2 . Example 2

[0120] This embodiment 2 provides a shock absorber based on anti-settling magnetorheological fluid, the structure of which is the same as that of embodiment 1. The anti-settling magnetorheological fluid provided in this specific embodiment and its preparation method are as follows:

[0121] The formula of the magnetorheological fluid provided in this embodiment is as follows:

[0122] Components Addition amount (wt%) Specific specifications / models No. 46 hydraulic oil Main body (balanced to 100%) Kinematic viscosity 45mPa·s (20℃) Fe@PE composite particles 18% <![CDATA[Core-shell structure: hollow iron core 500 nm; Fe3O4 layer 32 nm; PE layer 160 nm]]> graphite 1.5% Scale-like, particle size 1-3 μm Chlorinated paraffin (antiwear agent) 1.8% Chlorine content 52% Polyether thickener 2.0% Molecular weight 5000 Dialkyl dithiophosphates (antioxidants) 1.2% <![CDATA[Model T203]]> Alkylated naphthalene (pour point depressant) 0.7% Freezing point -40℃ Dimethyl silicone oil (defoaming agent) 0.8% Viscosity 1000 cSt

[0123] The preparation method is as follows:

[0124] Step 1: Magnetic particle pretreatment

[0125] Take hollow iron powder with a particle size of 500nm (density 2.3g / cm 3 ) 100g, placed in a vacuum drying oven, drying parameters: 175℃, vacuum degree 10Pa, time 2.5h.

[0126] PE coating preparation

[0127] Coating material: branched polyethylene wax (MW=3500) + 2wt% MAH-g-PE. The treated hollow iron powder and PE were mixed in a mass ratio of 100:3, stirred at 130°C (400 rpm) for 45 min, and passed through a 325 mesh (45 μm) sieve to obtain Fe@PE composite particles.

[0128] Step 2: Additive Mixing

[0129] Base fluid preparation: 500 mL of No. 46 hydraulic oil (kinematic viscosity 45 mPa·s@20°C);

[0130] Additive addition amount (based on the mass of hydraulic oil): graphite: 1.5wt%, chlorinated paraffin (anti-wear agent): 1.8wt%, polyether thickener (molecular weight 5000): 2.0wt%, dialkyl dithiophosphate (antioxidant): 1.2wt%, alkyl naphthalene (pour point depressant): 0.7wt%, dimethyl silicone oil (defoaming agent): 0.8wt%;

[0131] Mixing process: Stir at 8000 r / min for 30 min to obtain a mixed liquid.

[0132] Step 3: Magnetorheological fluid preparation

[0133] Primary dispersion: The pretreated Fe@PE composite particles were added to the mixture at a rate of 5 g / min and stirred at 8000 r / min for 40 min.

[0134] Secondary homogenization: transfer to a high-speed stirrer and stir at 28000r / min for 1h. Example 3

[0135] This embodiment 3 provides a shock absorber based on anti-settling magnetorheological fluid, the structure of which is the same as that of embodiment 1. The anti-settling magnetorheological fluid provided in this specific embodiment and its preparation method are as follows:

[0136] The formula of the magnetorheological fluid provided in this embodiment is as follows:

[0137] Components Addition amount (wt%) Specific specifications / models No. 46 hydraulic oil Balance to 100% Kinematic viscosity 45mPa·s (20℃) <![CDATA[Fe@Fe3O4@PE composite particles]]> 22% <![CDATA[Core-shell structure: hollow iron core 500 nm; Fe3O4 layer 40 nm; PE layer 200 nm]]> graphite 1.2% Scale-like, particle size 1-3 μm Chlorinated paraffin (antiwear agent) 2.2% Chlorine content 52% Polyether thickener 1.5% Molecular weight 5000 Dialkyl dithiophosphates (antioxidants) 1.0% <![CDATA[Model T203]]> Alkylated naphthalene (pour point depressant) 0.5% Freezing point -40℃ Dimethyl silicone oil (defoaming agent) 0.6% Viscosity 1000 cSt

[0138] The preparation method is as follows:

[0139] Step 1: Magnetic particle pretreatment

[0140] Fe3O4 transition layer construction:

[0141] Hollow iron powder with a particle size of 500 nm was plasma treated. The equipment parameters were: 100 W RF power, Ar / O2=4:1, treatment time 10 min, and surface roughness: Ra=85±5 nm measured by white light interferometry.

[0142] Chemical oxidation: Immerse the treated hollow iron powder in 0.1 mol / L FeCl3 solution (pH = 3.5). Reaction conditions: 70°C water bath, magnetic stirring (300 rpm), 30 min;

[0143] PE coating preparation

[0144] Coating material: branched polyethylene wax (MW=3500) + 2.5wt% MAH-g-PE. The treated hollow iron powder and PE were mixed in a mass ratio of 100:5, stirred at 130 °C (400 rpm) for 45 min, and passed through a 325 mesh (45 μm) sieve to obtain Fe@Fe3O4@PE composite particles.

[0145] Step 2: Additive Mixing

[0146] Base fluid preparation: 500 mL of No. 46 hydraulic oil (kinematic viscosity 45 mPa·s@20°C);

[0147] Additive addition amount (based on the mass of hydraulic oil): graphite: 1.2wt%, chlorinated paraffin (anti-wear agent): 2.2wt% (10g), polyether thickener (molecular weight 5000): 1.5wt% (9g), dialkyl dithiophosphate (antioxidant): 1.0wt% (7.5g), alkyl naphthalene (pour point depressant): 0.5wt% (4g), dimethyl silicone oil (defoaming agent): 0.6wt% (5g);

[0148] Mixing process: Stir at 8000 r / min for 30 min to obtain a mixed liquid.

[0149] Step 3: Magnetorheological fluid preparation

[0150] Primary dispersion: Add the pretreated Fe@Fe3O4@PE composite particles into the mixture at a rate of 5 g / min and stir at 7500 r / min for 40 min.

[0151] Secondary homogenization: transfer to a high-speed stirrer and stir at 30,000 rpm for 1 hour.

[0152] The thickness ratio of the Fe3O4 transition layer and the PE coating layer is calculated by the following formula:

[0153] ;

[0154] The parameters in the formula are shown in the table below:

[0155] Parameter Symbol Parameter value Data Source EPE 200 GPa Nanoindenter Test (Iron Core) EFe 0.8 GPa DMA dynamic mechanical analysis (PE coating) αFe <![CDATA[11.8×10 -6 K -1 ]]> Thermal dilatometer (NIST standard) αFe3O4 <![CDATA[8.5×10 -6 K -1 ]]> J. Appl. Phys. 112, 083534 αPE <![CDATA[150×10 -6 K -1 ]]> Polymer Eng.&Sci. 42(3) <![CDATA[γ Fe3O4 / c PE ]]> 0.5 Contact angle measurement (Owens-Wendt model) <![CDATA[γ Fe / c Fe3O4 ]]> 1.2 First-principles calculations r (iron powder particle size) 500 nm Laser particle size analyzer <![CDATA[r0 (Characteristic length)]]> 100 nm Theoretical model constant

[0156] The calculation result is η=0.20. Comparative Example 1

[0157] This comparative example 1 provides a shock absorber based on anti-settling magnetorheological fluid, the structure of which is the same as that of Example 1. The anti-settling magnetorheological fluid provided in this specific embodiment and its preparation method are as follows:

[0158] The formula of the magnetorheological fluid provided in this embodiment is as follows:

[0159] Components Addition amount (wt%) Specific specifications / models No. 46 hydraulic oil Balance to 100% Kinematic viscosity 45mPa·s (20℃) Ordinary carbonyl iron powder 25% <![CDATA[Particle size 5μm, density 7.8g / cm 3 > graphite 3% scaly, 1-3 μm Chlorinated paraffin (antiwear agent) 3% Chlorine content 52% Polyisobutylene thickener 2.5% Molecular weight 10000 dialkyl dithiophosphates 1.5% <![CDATA[Model T203]]> Dimethicone 1% Viscosity 1000 cSt

[0160] The preparation method is as follows:

[0161] Step 1: Magnetic particle pretreatment

[0162] Take carbonyl iron powder and place it in a vacuum drying oven with the drying parameters of 175°C, 10 Pa vacuum, and 2.5 h.

[0163] Step 2: Additive Mixing

[0164] Base fluid preparation: 500 mL of No. 46 hydraulic oil (kinematic viscosity 45 mPa·s@20°C);

[0165] Additive addition amount (based on the mass of hydraulic oil): graphite: 2wt% (10g), chlorinated paraffin (anti-wear agent): 2wt% (10g), polyether thickener (molecular weight 5000): 1.8wt% (9g), dialkyl dithiophosphate (antioxidant): 1.5wt% (7.5g), alkyl naphthalene (pour point depressant): 0.8wt% (4g), dimethyl silicone oil (defoaming agent): 1wt% (5g);

[0166] Mixing process: Stir at 8000 r / min for 30 min to obtain a mixed liquid.

[0167] Step 3: Magnetorheological fluid preparation

[0168] Initial dispersion: Add the pretreated hollow iron powder into the mixture at a rate of 5 g / min and stir at 9000 r / min for 40 min.

[0169] Secondary homogenization: transfer to a high-speed stirrer and stir at 25,000 r / min for 1 hour. Comparative Example 2

[0170] Comparative Example 2 provides a shock absorber based on anti-settling magnetorheological fluid, which has the same structure as Example 1. The anti-settling magnetorheological fluid provided in this specific embodiment and its preparation method are as follows: The formula of the magnetorheological fluid provided in this embodiment is as follows:

[0171] Components Addition amount (wt%) Specific specifications / models No. 46 hydraulic oil Balance to 100% Kinematic viscosity 45mPa·s (20℃) <![CDATA[Fe@ Fe3O4@PE composite particles]]> 22% <![CDATA[Core-shell structure: hollow iron core 500 nm; Fe3O4 layer 100 nm; PE layer 100 nm]]> graphite 1.2% Scale-like, particle size 1-3 μm Chlorinated paraffin (antiwear agent) 2.2% Chlorine content 52% Polyether thickener 1.5% Molecular weight 5000 Dialkyl dithiophosphates (antioxidants) 1.0% T203 type Alkylated naphthalene (pour point depressant) 0.5% Freezing point -40℃ Dimethyl silicone oil (defoaming agent) 0.6% Viscosity 1000 cSt

[0172] The preparation method is as follows:

[0173] Step 1: Magnetic particle pretreatment

[0174] Fe3O4 transition layer construction:

[0175] Hollow iron powder with a particle size of 500 nm was plasma treated. The equipment parameters were: 100 W RF power, Ar / O2=4:1, treatment time 10 min, and surface roughness: Ra=85±5 nm measured by white light interferometry.

[0176] Chemical oxidation: Immerse the treated hollow iron powder in 0.1 mol / L FeCl3 solution (pH = 3.5). Reaction conditions: 70°C water bath, magnetic stirring (300 rpm), 30 min;

[0177] PE coating preparation

[0178] Coating material: branched polyethylene wax (MW=3500) + 2.5wt% MAH-g-PE. The treated hollow iron powder and PE were mixed in a mass ratio of 100:5, stirred at 130°C (400 rpm) for 45 min, and passed through a 325 mesh (45 μm) sieve to obtain Fe@Fe3O4@PE composite particles.

[0179] Step 2: Additive Mixing

[0180] Base fluid preparation: 500 mL of No. 46 hydraulic oil (kinematic viscosity 45 mPa·s@20°C);

[0181] Additive addition amount (based on the mass of hydraulic oil): graphite: 1.2wt%, chlorinated paraffin (anti-wear agent): 2.2wt% (10g), polyether thickener (molecular weight 5000): 1.5wt% (9g), dialkyl dithiophosphate (antioxidant): 1.0wt% (7.5g), alkyl naphthalene (pour point depressant): 0.5wt% (4g), dimethyl silicone oil (defoaming agent): 0.6wt% (5g);

[0182] Mixing process: Stir at 8000 r / min for 30 min to obtain a mixed liquid.

[0183] Step 3: Magnetorheological fluid preparation

[0184] Primary dispersion: The pretreated Fe@Fe3O4@PE composite particles were added to the mixed solution at a rate of 5 g / min and stirred at 7500 r / min for 40 min.

[0185] Secondary homogenization: transfer to a high-speed stirrer and stir at 30,000 rpm for 1 hour.

[0186] Performance Testing

[0187] The following performance tests were performed on Examples 1 and 4 and Comparative Examples 1 and 2.

[0188] Test items Test standards Instruments and conditions Data collection method Sedimentation rate GB / T 265 Graduated cylinder method, let it stand at 25℃ and record the layer height Laser displacement sensor (accuracy ±0.1mm) Shear yield stress ISO 3219 Rheometer (magnetic field 0-1.5T, shear rate 1000s-1) Torque sensor (accuracy ±1%) Magnetic response time Homemade step magnetic field device 0→1T step, record the time when viscosity reaches 90% of the maximum value High-speed data acquisition card (sampling rate 10kHz) Interface bonding strength ASTM D903 Nanoindenter (Berkovich tip, loading rate 1 mN / s) Force-displacement curve analysis Wear performance ASTM D4172 Four-ball testing machine (load 392N, speed 1200rpm) Wear spot diameter measurement using an optical microscope Low temperature fluidity ASTM D2983 -30℃ constant temperature box, measure the time it takes to pass through the filter Timer recording (accuracy ±0.1s) Coating integrity rate SEM statistical method Scanning electron microscope (10kV, 50,000x magnification) Image analysis software calculates the proportion of damaged area

[0189] Performance test results

[0190] Test items Example 1 Comparative Example 2 (Single PE Coating) Example 4 Comparative Example 1 (no coating) Comparative Example 2 (η=0.50) Test standards Sedimentation rate (500h, %) 4.8 7.5 2.3 Fully layered 5.8 GB / T 265 Shear stress (1T, kPa) 48 42 78 35 50 ISO 3219 Magnetic response time (ms) 18 22 10 25 18 Step magnetic field test Interface strength (N / m) - 6 18 - 10 ASTM D903 Wear spot diameter (mm) 0.82 0.65 0.38 0.95 0.52 ASTM D4172 -40℃ fluidity pass Pass slowly Fast Pass Gelation pass ASTM D2983 Performance retention rate after aging at 120℃ for 100h 85% 62% 95% Failure 75% High temperature cycle test <![CDATA[10 5 Complete coverage rate after first shearing]]> - 58% 96% - 72% SEM statistical method

[0191] Note: Sedimentation rate: After standing at 25℃ for 500 hours, measure the height percentage of the clarified layer;

[0192] Shear stress: Rheometer in 1T magnetic field, 1000s -1 Measured under shear rate;

[0193] Magnetic response time: When the magnetic field changes from 0 to 1T, the time for the viscosity to reach 90% of the maximum value is recorded;

[0194] Wear spot test: The four-ball machine was operated under a load of 392N for 1 hour, and the wear diameter of the steel balls was measured.

[0195] A comparative analysis of the magnetorheological fluid performance test results of Examples 1 and 4, as well as Comparative Examples 1 and 2, reveals that the three-layer coating structure (Fe-Fe₃O₄-PE) of the present invention exhibits significant advantages. In terms of sedimentation resistance, Example 3 achieved a 500-hour sedimentation rate of only 2.3%, a 69% decrease compared to Comparative Example 2 (single PE coating) and significantly superior to the traditional uncoated formulation (Comparative Example 1, which exhibited complete delamination). This is attributed to the synergistic effect of the Fe₃O₄ transition layer (40nm) and the PE coating layer (80nm): the transition layer enhances interfacial bonding strength (18N / m) through chemical bonding, while the steric hindrance of the PE layer effectively inhibits particle agglomeration. Regarding magnetorheological properties, Example 3 achieved a shear stress of 78kPa and a response time of only 10ms at a 1T magnetic field, improvements of 86% and 55% compared to Example 2, respectively. This is attributed to the efficient magnetic field penetration (loss <5%) achieved by the optimized thickness ratio (η = 0.20). Durability testing further validated its superiority. After 105 shear cycles, Example 3 maintained a 96% coating integrity rate and exhibited performance fluctuations of less than 5% across a wide temperature range of -40°C to 120°C, while the control samples all experienced interface failure or a sudden drop in performance. These results fully demonstrate that the present invention, through the formulaic control of the gradient coating structure and thickness ratio, achieves a breakthrough balance in sedimentation stability, magnetic response speed, and environmental adaptability.

[0196] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A shock absorber based on anti-settling magnetorheological fluid, characterized in that: The invention comprises an outer cylinder (1) and a floating piston (4); the floating piston (4) is slidably mounted at the lower inner portion of the outer cylinder (1); the floating piston (4) divides the inner portion of the outer cylinder (1) into a working chamber and a gas chamber; the gas chamber is located at the lower portion of the outer cylinder (1); the gas chamber is filled with nitrogen; and the working chamber is filled with anti-sedimentation magnetorheological fluid; a piston assembly is slidably mounted in the outer cylinder (1) to divide the inner working chamber of the outer cylinder (1) into an upper chamber and a lower chamber; an excitation coil (7) is provided. A winding is arranged on the outside of the outer cylinder (1) or integrated in the piston assembly, and is used to generate a controllable magnetic field; a damping channel (6) is opened in the piston assembly, and the damping channel (6) is spiral, linear or broken line-shaped; an acceleration sensor (5) is arranged at the end of the outer cylinder (1) and is used to monitor the vibration signal in real time; a reset spring (10) is arranged between the outer cylinder (1) and the piston assembly, and the reset spring (10) is used to provide elastic buffering force, and cooperates with the floating piston (4) to form an anti-collision buffer mechanism; The method for preparing the anti-settling magnetorheological fluid comprises the following steps: pre-treating the magnetic particles: drying the hollow iron powder; mixing the additives: adding graphite, a thickener, an antioxidant, a pour point depressant, a stabilizer, and a defoaming agent to hydraulic oil and dissolving them to form a uniform mixed liquid; initial stirring and dispersing: slowly adding the dried hollow iron powder to the mixed liquid and stirring to preliminarily disperse the magnetic particles; and secondary stirring and homogenizing: pouring the magnetic particles and the mixed liquid into a high-speed stirrer and stirring them at a high speed of 20,000-30,000 r / min to obtain the anti-settling magnetorheological fluid. The composite particles are formed by coating a polyethylene layer on the surface of the hollow iron powder, and further comprising an Fe3O4 transition layer between the hollow iron powder and the polyethylene layer, thereby forming a three-layer composite particle. The Fe3O4 transition layer is prepared by treating the hollow iron powder in Ar / O2 plasma to form nano-scale oxide protrusions on the surface, and then drying the hollow iron powder; and reacting the treated hollow iron powder with a FeCl3 solution to form an Fe3O4 transition layer on the surface.

2. The shock absorber based on anti-settling magnetorheological fluid according to claim 1, characterized in that: The piston assembly comprises a coaxially arranged piston rod (2) and a damping piston head (3), wherein the piston rod (2) is hollow, and the damping channel (6) extends in a spiral, straight or broken line shape in the damping piston head (3). The outer periphery of the damping piston head (3) is provided with an annular groove, and the excitation coil (7) is embedded in the groove. A magnetic conductive material is provided between the excitation coil (7) and the damping channel (6) for enhancing the magnetic field strength in the damping channel (6). The excitation coil (7) is electrically connected to an external controller through the hollow piston rod (2), and the piston rod (2) is used to transmit a control current to adjust the The magnetic field strength generated by the excitation coil (7); a sealing ring (8), installed on the outer side of the annular groove on the outer periphery of the damping piston head (3), for isolating the excitation coil (7) from contact with the anti-sedimentation magnetorheological fluid; a return spring (10), provided between the outer cylinder (1) and the piston rod (2), the return spring (10) being used to provide elastic buffering force, and cooperating with the floating piston (4) to form an anti-collision buffering mechanism; the gap width of the damping channel (6) is 0.2~1.0mm, and the channel surface is plated with a tungsten carbide wear-resistant layer; an axial groove (9) is provided at the working chamber position on the inner wall of the outer cylinder (1), and the groove depth is 0.5-2mm.

3. The shock absorber based on anti-settling magnetorheological fluid according to claim 1, characterized in that: The hollow iron powder is a composite particle with a polyethylene layer coated on the surface of the hollow iron powder. The preparation method includes: mixing the dried hollow iron powder with molecular weight polyethylene; heating to 110-150°C under nitrogen protection to melt and coat; and grading through a 200-400 mesh sieve after cooling to form a coating layer.

4. The shock absorber based on anti-settling magnetorheological fluid according to claim 1, characterized in that: The preparation method of the three-layer structure composite particles is as follows: treating hollow iron powder in Ar / O2 plasma to form nano-scale oxide protrusions on the surface, and drying; reacting the dried hollow iron powder with FeCl3 solution to form an Fe3O4 transition layer on the surface; mixing a branched polyethylene wax containing 1-3wt% maleic anhydride grafted polyethylene with the hollow iron powder, and melt-coating the mixture; and grading the mixture through a 200-400 mesh sieve after cooling to form a coating layer.

5. The shock absorber based on anti-settling magnetorheological fluid according to claim 1, characterized in that: The particle size of the hollow iron powder is 300-600 nm.

6. The shock absorber based on anti-settling magnetorheological fluid according to claim 1, characterized in that: The kinematic viscosity of the hydraulic oil at 20° C. is 20-60 mPa·s.

7. The shock absorber based on anti-settling magnetorheological fluid according to claim 1, characterized in that: The graphite addition amount is 1%-3% of the hydraulic oil mass, the antioxidant addition amount is 1%-2% of the hydraulic oil mass, the pour point depressant addition amount is 0.5%-1% of the hydraulic oil mass, the thickener addition amount is 1%-2.5% of the hydraulic oil mass, the stabilizer addition amount is 1%-2% of the hydraulic oil mass, the anti-wear agent addition amount is 1%-3% of the hydraulic oil mass, and the defoaming agent addition amount is 1% of the hydraulic oil mass.

8. The shock absorber based on anti-settling magnetorheological fluid according to claim 1, characterized in that: The rotation speed of the initial stirring and dispersing is 5000-10000 r / min.

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