阅读说明：本技术 纳米磁流体间隙密封高速液压缸 (Nano magnetic fluid gap sealing high-speed hydraulic cylinder ) 是由 蒋佳骏 吴张永 朱启晨 莫子勇 叶艺明 叶淳健 张沧 于 2021-08-24 设计创作，主要内容包括：本发明涉及纳米磁流体间隙密封高速液压缸,属于液压传动技术领域。本发明包括活塞杆,有杆腔缸盖,有杆腔油口,电磁铁,有杆腔缓冲腔,缸筒,有杆腔缓冲头,活塞,微磁阵列功能表面,无杆腔缓冲头,无杆腔缓冲腔,无杆腔油口,无感腔缸盖。本发明采用纳米磁流体为工作介质,分散稳定性、流动性好,具有较好的磁-粘调控特性。设置了电磁铁调控缓冲腔纳米磁流体介质粘度,提高液压缸缓冲性能。活塞与缸筒采用间隙密封形式,活塞上设置的微磁阵列功能表面与纳米磁流体耦合形成润滑膜,提高了润滑和密封特性特性,有利于液压缸的高速性能。(The invention relates to a nano magnetic fluid gap sealing high-speed hydraulic cylinder, belonging to the technical field of hydraulic transmission. The invention comprises a piston rod, a cylinder cover with a rod cavity, an oil port with the rod cavity, an electromagnet, a buffer cavity with the rod cavity, a cylinder barrel, a buffer head with the rod cavity, a piston, a micro-magnetic array functional surface, a buffer head without the rod cavity, a buffer cavity without the rod cavity, an oil port without the rod cavity and a cylinder cover without a sensing cavity. The invention adopts the nano magnetic fluid as the working medium, has good dispersion stability and fluidity and has better magnetic-viscous regulation and control characteristics. The electromagnet is arranged to regulate and control the viscosity of the nanometer magnetic fluid medium in the buffer cavity, so that the buffer performance of the hydraulic cylinder is improved. The piston and the cylinder barrel adopt a gap sealing mode, and the micro-magnetic array functional surface arranged on the piston is coupled with the nano-magnetic fluid to form a lubricating film, so that the lubricating and sealing characteristic characteristics are improved, and the high-speed performance of the hydraulic cylinder is facilitated.)

1. A high-speed pneumatic cylinder of nanometer magnetic current body clearance seal which characterized in that: the device comprises a piston rod (1), a cylinder cover (2) with a rod cavity, an oil port (3) with the rod cavity, an electromagnet (4), a buffer cavity (5) with the rod cavity, a cylinder barrel (6), a buffer head (7) with the rod cavity, a piston (8), a micro-magnetic array functional surface (9), a buffer head (10) without the rod cavity, a buffer cavity without the rod cavity (11), an oil port (12) without the rod cavity and a cylinder cover (13) without a sensing cavity;

a rod cavity oil port (3) and a rod cavity buffer cavity (5) communicated with the rod cavity oil port (3) are arranged on the rod cavity cylinder cover (2);

one end of the piston (8) is provided with a rod cavity buffer head (7), the other end of the piston is provided with a rodless cavity buffer head (10), and the surface of the piston (8) is provided with a micro-magnetic array functional surface (9);

a rodless cavity buffer cavity (11) and a rodless cavity oil port (12) are arranged on the rodless cavity cylinder cover (13), and the rodless cavity buffer cavity (11) is communicated with the rodless cavity oil port (12);

the piston (8) is positioned in the cylinder barrel (6), one end of the piston rod (1) is inserted into the cylinder barrel (6) and is connected with the piston (8), and the other end of the piston rod is positioned outside the cylinder barrel (6);

the cylinder cover (2) with the rod cavity penetrates through one end, located outside the cylinder barrel (6), of the piston rod (1) and then is inserted into the cylinder barrel (6);

noninductive chamber cylinder cap (13) insert cylinder (6), electro-magnet (4) are installed at cylinder (6) both ends, electro-magnet (4) are four, and two electro-magnet (4) are a set of, and parallel installation is in same one side of cylinder (6) each other, and every group electro-magnet (4) need satisfy the magnetic field that its production covers its cushion chamber that corresponds completely.

2. The nano-magnetic fluid gap sealing high-speed hydraulic cylinder according to claim 1, characterized in that: the piston (8) is in clearance fit with the cylinder barrel (6), and the size of the clearance is 20-50 microns.

3. The nano-magnetic fluid gap sealing high-speed hydraulic cylinder according to claim 1, characterized in that: the electromagnet (4) comprises a magnetic conduction core (4-1), a magnetic conduction sleeve (4-2) and an electromagnetic coil (4-3); the magnetic conduction core (4-1) is arranged in the magnetic conduction sleeve (4-2), and the electromagnetic coil (4-3) is wound on the magnetic conduction core (4-1).

4. The nano-magnetic fluid gap sealing high-speed hydraulic cylinder according to claim 3, characterized in that: the electromagnetic coil (4-3) is a copper wire, and the ampere-turn number is larger than 800.

5. The nano-magnetic fluid gap sealing high-speed hydraulic cylinder according to claim 3 or 4, characterized in that: the magnetic conducting core (4-1) and the magnetic conducting sleeve (4-2) are made of permalloy materials or super permalloy materials, and the label is not lower than 1J 50.

6. The nano-magnetic fluid gap sealing high-speed hydraulic cylinder according to claim 1, characterized in that: the micro magnetic array functional surface (9) comprises a micro annular groove (9-1) and a micro permanent magnet (9-2), the micro annular groove (9-1) is processed on the piston (8) by laser, and the micro permanent magnet (9-2) is prepared in the micro annular groove (9-1) by a deposition method.

7. The nano-magnetic fluid gap-sealed high-speed hydraulic cylinder according to claim 6, wherein: the section of the miniature circular groove (9-1) is rectangular, the groove depth is 10-12 microns, the groove width is 30-32 microns, and the distance between the grooves is 30-32 microns.

8. The nano-magnetic fluid gap sealing high-speed hydraulic cylinder according to claim 6 or 7, characterized in that: the miniature permanent magnets (9-2) are made of neodymium iron boron permanent magnet materials, the thickness of the miniature permanent magnets is 30 micrometers, the magnetizing directions are unified to "±", or the miniature permanent magnets are magnetized according to a four-module Halbach array, and "→ ± ↓" is a group of arrays.

9. The nano-magnetic fluid gap sealing high-speed hydraulic cylinder according to claim 1, characterized in that: the diameter of the rod cavity buffer head (7) and the rodless cavity buffer head (10) is 40% -60% of that of the piston (8), the annular gap between the rod cavity buffer head (7) and the rod cavity buffer cavity (5) is 0.5-2.5 mm, and the annular gap between the rodless cavity buffer head (10) and the rodless cavity buffer cavity (11) is 0.5-2.5 mm.

10. The nano-magnetic fluid gap sealing high-speed hydraulic cylinder according to claim 1, characterized in that: the cylinder barrel (6) is made of aluminum alloy or austenitic stainless steel which is not attracted by the permanent magnet, and the surface roughness of the cylinder barrel is less than Ra0.4.

Technical Field

The invention relates to a nano magnetic fluid gap sealing high-speed hydraulic cylinder, and belongs to the technical field of hydraulic transmission.

Background

The nanometer magnetic fluid is an intelligent fluid which is formed by uniformly dispersing magnetic particles with the particle size of less than 10nm in a base fluid and has magnetism and fluidity, the viscosity of the intelligent fluid can be rapidly increased (in milliseconds) under the action of a magnetic field, and the change is controllable and reversible and is called as a magneto-rheological effect. Compared with the magnetic rheological fluid (with micron-sized particle size) and the common magnetic fluid (with 1-100nm particle size), the nano magnetic fluid has more stable performance, is not easy to agglomerate or precipitate, has the advantages of good fluidity, sealing property, lubricating property and the like, and meets the requirements of hydraulic transmission characteristics. The nano magnetic fluid is applied to the hydraulic transmission medium, has the positive prospect of developing more efficient, energy-saving and intelligent hydraulic elements and systems, and is more beneficial to developing special hydraulic elements and systems applied to special working occasions and extreme working conditions. In the prior art, no report of a nano magnetofluid hydraulic element is found. Therefore, the research and development of the hydraulic element which is matched with the magnetic fluid hydraulic medium and gives full play to the performance advantages of the magnetic fluid hydraulic medium is urgent and important.

In a hydraulic system, a hydraulic cylinder is a hydraulic actuator which converts hydraulic energy into mechanical energy and performs linear reciprocating motion or oscillating motion. The working characteristics of the hydraulic cylinder are seriously influenced by the good and bad lubricating and sealing performances between the piston and the cylinder barrel of the hydraulic cylinder: (1) the sealing element is not well matched or a clearance sealing mode is adopted, so that leakage between two cavities of the hydraulic cylinder is caused, volume loss is caused, and the working efficiency and the positioning precision of the hydraulic cylinder are influenced. (2) If the sealing piece is too tightly matched, a large friction force is generated when the piston moves, the friction and the abrasion of the cylinder barrel and the sealing piece are easily caused, great mechanical loss is caused, and the working efficiency and the dynamic characteristic of the hydraulic cylinder are influenced. (3) The existing sealing elements have abrasion, plastic deformation, even fatigue fracture and the like of different degrees in long-time use, and the working performance and the service life of the hydraulic cylinder are seriously influenced. (4) When the hydraulic cylinder is started, a lubricating medium is lacked between the sealing piece and the cylinder barrel, dry friction is easy to occur, and the control performance of the hydraulic cylinder is affected. (5) In particular, for a high-speed servo hydraulic cylinder with high requirements on dynamic characteristics and positioning accuracy, the sealing is required to ensure less leakage and have lower frictional resistance. Pneumatic cylinder stroke can produce inertial impact to the terminal time, leads to impact vibration and noise, seriously influences life, adopts the outer buffer of jar in the jar to above-mentioned problem prior art, but current jar buffer can not accomplish self-adaptation intelligent control, because buffer's throttle design, often leads to the pneumatic cylinder start-up to accelerate slowly, the energy consumption is high. Although the existing outside-cylinder buffer device or buffer loop can be regulated and controlled according to different working conditions of the hydraulic cylinder, the better buffer effect is achieved, but the device is complex in structure, the buffer loop occupies large space, and the regulation and control response speed of the buffer characteristic is low.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a nano magnetic fluid hydraulic cylinder taking nano magnetic fluid as a working medium, solve the problem that the sealing property and the lubricating property are difficult to meet simultaneously when the hydraulic cylinder runs at a high speed, solve the problems of abrasion and fatigue of the existing piston sealing element and improve the buffer property of the hydraulic cylinder.

The technical scheme of the invention is as follows: a high-speed hydraulic cylinder with a nano-magnetic fluid gap seal comprises a piston rod, a cylinder cover with a rod cavity, an oil port with the rod cavity, an electromagnet, a buffer cavity with the rod cavity, a cylinder barrel, a buffer head with the rod cavity, a piston, a micro-magnetic array functional surface, a buffer head without the rod cavity, a buffer cavity without the rod cavity, an oil port without the rod cavity and a cylinder cover without a sensing cavity.

The rod cavity cylinder cover is provided with a rod cavity oil port and a rod cavity buffer cavity communicated with the rod cavity oil port, and the rod cavity buffer cavity is positioned in the middle of the rod cavity cylinder cover.

One end of the piston is provided with a rod cavity buffer head, the other end of the piston is provided with a rodless cavity buffer head, and the surface of the piston is provided with a micro-magnetic array functional surface.

A rodless cavity buffer cavity and a rodless cavity oil port are formed in the rodless cavity cylinder cover, and the rodless cavity buffer cavity is communicated with the rodless cavity oil port.

The piston is positioned in the cylinder barrel and is in clearance fit with the cylinder barrel, and the size of the clearance is 20-50 microns. One end of the piston rod is inserted into the cylinder barrel and connected with the piston, and the other end of the piston rod is positioned outside the cylinder barrel.

The rod cavity cylinder cover penetrates through one end, located outside the cylinder barrel, of the piston rod and then is inserted into the cylinder barrel, and the rod cavity cylinder cover is tightly matched with the cylinder barrel.

The non-sensing cavity cylinder cover is inserted into the cylinder barrel, and electromagnets are installed at two ends of the cylinder barrel. The number of the electromagnets is four, the two electromagnets are in one group and are arranged on the same side of the cylinder barrel in parallel, and each group of electromagnets is required to generate a magnetic field which completely covers the corresponding buffer cavity.

The electromagnet comprises a magnetic conduction core, a magnetic conduction sleeve and an electromagnetic coil; the magnetic conduction core is arranged in the magnetic conduction sleeve, and the electromagnetic coil is wound on the magnetic conduction core.

The electromagnetic coil is a copper wire, and the ampere-turn number is larger than 800.

The magnetic core and the magnetic sleeve are made of soft magnetic materials such as permalloy materials or super permalloy materials, and the label is not lower than 1J 50.

The micro magnetic array functional surface comprises a micro annular groove and a micro permanent magnet, the micro annular groove is processed on the piston by laser, and the micro permanent magnet is prepared in the micro annular groove by a deposition method.

The section of the miniature circular groove is rectangular, the groove depth is 10-12 microns, the groove width is 30-32 microns, and the distance between the grooves is 30-32 microns.

The miniature permanent magnet is neodymium iron boron permanent magnet material, and thickness is 30 microns, and the direction of magnetizing is unified to "↓", or magnetizes according to four module halbach array, "→ ↓" is a set of array.

The diameters of the buffer head with the rod cavity and the buffer head without the rod cavity are 40-60% of the diameter of the piston, and the annular gap between the buffer head and the buffer cavity is 0.5-2.5 mm.

The cylinder barrel is made of aluminum alloy or austenitic stainless steel which is not attracted by the permanent magnet, and the surface roughness of the cylinder barrel is less than Ra0.4.

The working medium of the nano magnetic fluid hydraulic cylinder is nano magnetic fluid which can be hydraulic oil-based, silicon oil-based or water-based magnetic liquid, the addition amount of the magnetic particles is 1.5-5 wt%, the average particle size of the magnetic particles is less than 10nm, and when the base liquid is water-based, a tackifier is added to improve the viscosity.

The invention takes the nanometer magnetic fluid as the working medium, has better magnetic-viscous regulation and control characteristics, and avoids the problems that the magnetic rheological fluid and the ordinary magnetic fluid are easy to generate agglomeration or precipitation, thereby having poor fluidity, being easy to cause abrasive wear and the like. The size of a single particle of the nano magnetic fluid is 100 molecular levels, which is far smaller than the micron-sized impurity standard in the cleanliness of a hydraulic medium, and meets the basic characteristic requirements of hydraulic transmission on the cleanliness, the mobility, the lubricity and the like of a working medium.

The micro-magnetic array functional surface is arranged on the surface of the piston, a gap sealing mode is adopted between the piston and the cylinder barrel, the magnetic-viscous effect of the nano-magnetic fluid hydraulic medium is utilized, and the micro-magnetic array functional surface is coupled with the nano-magnetic fluid hydraulic medium, so that a high-viscosity lubricating film is formed in a sealing gap, the problems of abrasion and fatigue of the existing piston sealing element are solved, the problems of low frequency response and low control precision of a high-speed hydraulic cylinder caused by the limitation of the material properties of the medium and the sealing element in the prior art are solved, and the technical problem that the sealing property and the lubricating property are difficult to meet when the hydraulic cylinder runs at a high speed is solved.

The electromagnets are arranged in the buffer cavities at the two ends of the hydraulic cylinder, the electromagnets are used for generating a controllable magnetic field, viscosity regulation and control are carried out on the nano magnetic fluid hydraulic medium in the buffer cavities, the viscosity-induced damping coefficient of the medium is changed, the effect of throttling-viscosity-induced damping composite buffering is achieved, the buffer damping size can be adjusted according to different working conditions, and self-adaptive control of buffering is achieved. The problems that in the prior art, an in-cylinder buffer device cannot achieve self-adaptive intelligent regulation and control, hydraulic cylinder starting acceleration is slow, and energy consumption is high are solved. The problems that an existing cylinder outer buffer device or a buffer loop device is complex in structure, large in occupied space of the buffer loop, and low in regulation response speed of the buffer characteristic are solved.

The invention has the beneficial effects that:

1. the nano magnetic fluid hydraulic cylinder adopts the nano magnetic fluid as a working medium, and has good dispersion stability and fluidity.

2. The nano magnetic fluid hydraulic cylinder adopts a clearance sealing mode, avoids the frictional wear of the sealing piece and the cylinder barrel and is beneficial to the high-speed performance of the hydraulic cylinder.

3. The magnetic field generated by the micro-magnetic array functional surface acts on the nano magnetic fluid hydraulic medium, a high-viscosity lubricating film can be formed in the sealing gap, and the sealing performance of the piston under low-speed and heavy-load operation is improved.

4. The micro-magnetic array functional surface annular microgrooves play a role in pressure equalization, can form oil film lubrication when the piston runs at a high speed, and improve the sealing performance and the lubricating performance of the piston under the high-speed motion.

5. The magnetic field generated by the functional surface of the micro-magnetic array acts on the nano-magnetic fluid hydraulic medium, so that the lubricating medium in the gap can be supplemented, and the dry friction when the hydraulic cylinder is started is avoided.

6. The damping mode adopted by the invention has a simple and reliable structure, can regulate and control the damping resistance, realizes the self-adaptive control of the damping of the hydraulic cylinder, and can absorb the vibration in the variable cross-section throttling process.

7. The nano-magnetic fluid hydraulic cylinder has excellent high-speed performance, high control precision and quick control response.

8. The electromagnet adopts high-permeability materials, so that the magnetic field is concentrated on one side of the buffer cavity as far as possible, the utilization efficiency of the magnetic field is improved, and the interference of the magnetic field to the external environment is reduced.

9. The Halbach magnetizing scheme of the micro-magnetic array functional surface of the invention concentrates magnetic energy on one side of the gap as much as possible, improves the utilization efficiency of a magnetic field, ensures that high-viscosity areas of the gap are distributed continuously, has better lubricating and sealing performances and is suitable for hydraulic cylinders with extremely strict requirements on high-speed performance.

Drawings

FIG. 1 is a cross-sectional view of the present invention;

in the figure: 1-a piston rod, 2-a cylinder cover with a rod cavity, 3-an oil port with a rod cavity, 4-an electromagnet, 5-a buffer cavity with a rod cavity, 6-a cylinder barrel, 7-a buffer head with a rod cavity, 8-a piston, 9-a micro-magnetic array functional surface, 10-a buffer head without a rod cavity, 11-a buffer cavity without a rod cavity, 12-an oil port without a rod cavity and 13-a cylinder cover without an induction cavity.

FIG. 2 is a cross-sectional view of an electromagnet according to the present invention;

in the figure: 4-1-magnetic core, 4-2-magnetic sleeve and 4-3-electromagnetic coil.

FIG. 3 is a partial cross-sectional view of a micro-magnetic array functional surface seal gap according to the present invention;

in the figure: 6-cylinder barrel, 8-piston, 9-1-miniature circular groove and 9-2 miniature permanent magnet.

FIG. 4 is a schematic diagram of the Halbach magnetizing scheme of the micro-magnetic array functional surface sealing gap.

FIG. 5 is a schematic view of a common magnetization scheme of the micro-magnetic array functional surface sealing gap according to the present invention.

Fig. 6 is a buffer schematic of the present invention.

Detailed Description

The invention is further described with reference to the following drawings and detailed description.

As shown in fig. 1, the nano-magnetic fluid gap-sealed high-speed hydraulic cylinder comprises a piston rod 1, a rod cavity cylinder cover 2, a rod cavity oil port 3, an electromagnet 4, a rod cavity buffer cavity 5, a cylinder barrel 6, a rod cavity buffer head 7, a piston 8, a micro-magnetic array functional surface 9, a rodless cavity buffer head 10, a rodless cavity buffer cavity 11, a rodless cavity oil port 12 and a non-sensing cavity cylinder cover 13.

The rod cavity cylinder cover 2 is provided with a rod cavity oil port 3 and a rod cavity buffer cavity 5 communicated with the rod cavity oil port 3, and the rod cavity buffer cavity 5 is positioned in the middle of the rod cavity cylinder cover 2.

One end of the piston 8 is provided with a rod cavity buffer head 7, the other end of the piston is provided with a rodless cavity buffer head 10, and the surface of the piston 8 is provided with a micro-magnetic array functional surface 9.

The non-sensing cavity cylinder cover 13 is provided with a non-rod cavity buffer cavity 11 and a non-rod cavity oil port 12, and the non-rod cavity buffer cavity 11 is communicated with the non-rod cavity oil port 12.

The piston 8 is positioned in the cylinder barrel 6 and is in clearance fit with the cylinder barrel 6, and the size of the clearance is 20-50 microns. One end of the piston rod 1 is inserted into the cylinder 6 and is connected with the piston 8 through threads, and the other end of the piston rod is positioned outside the cylinder 6.

The rod cavity cylinder cover 2 penetrates through one end, located outside the cylinder barrel 6, of the piston rod 1 and then is inserted into the cylinder barrel 6, and the rod cavity cylinder cover 2 is tightly matched with the cylinder barrel 6.

The non-sensing cavity cylinder cover 13 is inserted into the cylinder barrel 6, and the electromagnets 4 are mounted at two ends of the cylinder barrel 6 and connected with the cylinder barrel 6 in a bonding mode. The number of the electromagnets 4 is four, the two electromagnets 4 are in one group and are arranged on the same side of the cylinder barrel 6 in parallel, and each group of electromagnets 4 needs to generate a magnetic field which completely covers the corresponding buffer cavity. As shown in fig. 6, two electromagnets 4 are installed on the right side of the cylinder 6 in the figure, and are respectively located at the upper end and the lower end of the left side of the cylinder 6, and magnetic fields generated by the two electromagnets completely cover the corresponding rodless chamber buffer chambers 11. The rodless cavity buffer cavity 11 is filled with a uniform magnetic field, and the viscosity of the nano magnetic fluid medium in the rodless cavity buffer cavity 11 is changed, so that the magnitude of the buffer damping force is controlled. The rod cavity buffer cavity 5 at the left side of the cylinder barrel 6 also meets the condition that the magnetic field generated by the corresponding electromagnet 4 completely covers the cavity.

As shown in fig. 2, the electromagnet 4 comprises a magnetic core 4-1, a magnetic sleeve 4-2 and an electromagnetic coil 4-3; the magnetic conducting core 4-1 is arranged in the magnetic conducting sleeve 4-2, and the electromagnetic coil 4-3 is wound on the magnetic conducting core 4-1.

The electromagnetic coil 4-3 is a copper wire, and the ampere-turn number is larger than 800.

The magnetic core 4-1 and the magnetic sleeve 4-2 are made of permalloy materials or super permalloy materials and other soft magnetic materials, and the label is not lower than 1J 50.

The piston rod 1, the cylinder cover 2 with the rod cavity, the cylinder barrel 6, the buffer head 7 with the rod cavity, the piston 8, the buffer head 10 without the rod cavity, the buffer cavity 11 without the rod cavity and the cylinder cover 13 without the induction cavity are made of low paramagnetic materials such as aluminum alloy or austenitic stainless steel (304 stainless steel) which are not attracted by the permanent magnet

The surface roughness of the cylinder barrel 6 is less than Ra0.4.

The diameters of the rod cavity buffer head 7 and the rodless cavity buffer head 10 are 40-60% of the diameter of the piston 8, and the annular gap between the buffer heads and the buffer cavity is 0.5-2.5 mm.

As shown in fig. 3, the micro magnetic array functional surface 9 includes a micro circular groove 9-1 and a micro permanent magnet 9-2, the micro circular groove 9-1 is processed on the piston 8 by laser, and the micro permanent magnet 9-2 is prepared in the micro circular groove 9-1 by a deposition method.

The section of the miniature circular groove 9-1 is rectangular, the groove depth is 10-12 microns, the groove width is 30-32 microns, and the distance between the grooves is 30-32 microns.

The miniature permanent magnets 9-2 are neodymium iron boron permanent magnet materials, the thickness is 30 microns, the magnetizing directions are unified to "±", or magnetize according to four-module halbach array, "→ ± + ↓" is a set of array, can constitute by the multiunit according to the demand, and the magnetizing direction is as shown in fig. 4.

The processing method of the micro-magnetic array functional surface 9 specifically comprises the following steps:

step 1: the surface of the piston is polished by using SiC sand paper with the grain diameter of 0.5 micron, so that defects and scratches are eliminated as far as possible.

Step 2: and cleaning the surface of the piston by using deionized water to remove impurities such as particles, abrasive dust and the like.

Step 3: annular microgrooves with the depth of 40 microns, the width of 30 microns and the distance of 30 microns are machined on the surface of the piston by a laser marking machine.

Step 4: and (3) polishing the surface of the piston and the annular microgrooves by utilizing nano SiC powder with the particle size of 100 nm.

Step 5: washing the surface with deionized water, cleaning the piston in an ultrasonic cleaner for 5min, taking out, washing the surface with deionized water to remove impurities such as particles and abrasive dust, and drying in a drying oven at 40 deg.C.

Step 6: FeCl2 & 4H2O and NdCl3 & 6H2O are used as main salts, glycine is used as a complexing agent, H3BO3 is used as an auxiliary additive, and electrodeposition is carried out under the conditions that the pH value is 2.5-3.0, the temperature is 30 ℃, and the potential is-2V, so that a dense neodymium iron boron material thin layer with uniform thickness is obtained on the surface of the piston.

Step 7: and (3) polishing and removing the neodymium iron boron thin layer on the surface of the piston by using 0.5-micron SiC abrasive paper, and only keeping the neodymium iron boron thin layer in the annular micro-groove.

Step 8: and magnetizing the thin neodymium iron boron layer by using magnetizing equipment according to the graph shown in figure 4 or figure 5, wherein the magnetic performance of the magnetized neodymium iron boron permanent magnet is not lower than that of the permanent magnet marked by N35.

The working principle of the invention is as follows:

1. principle of buffering

(1) The buffer principle of the rodless cavity is as follows: the nanometer magnetic fluid hydraulic medium with pressure enters the rod cavity of the hydraulic cylinder from the rod cavity oil port 3 to push the piston 8 to move towards the rodless cavity cylinder cover 13, and the hydraulic medium in the rodless cavity flows through the rodless cavity buffer cavity 11 and flows out of the rodless cavity oil port 12 to flow back to the oil tank. Along with the movement of the piston 8 to the rodless cavity cylinder cover 13, the rodless cavity buffer head 10 is gradually close to the rodless cavity buffer cavity 11, when the rodless cavity buffer head 10 is inserted into the rodless cavity buffer cavity 11, a radial gap is formed between the rodless cavity buffer head 10 and the rodless cavity buffer cavity 11, the through-flow sectional area of the hydraulic medium is instantly reduced, the through-flow resistance of the hydraulic medium is increased, and the effect of blocking the movement of the piston 8 is formed. Meanwhile, the electromagnet 4 is electrified to generate a magnetic field as shown in fig. 5, the viscosity of the nano magnetic fluid hydraulic medium is increased under the action of the magnetic field, and a high-viscosity area is formed in the buffer cavity, so that the through-flow damping coefficient is increased, the resistance borne by the piston cylinder is increased, and the vibration caused by the variable through-flow section is absorbed. Under the variable cross-section throttling and viscosity regulating effects, the piston 8 is decelerated by a large and stable damping force, so that a buffering effect is achieved. When the piston 8 reaches the terminal, the electromagnet 4 is powered off, the magnetic field is eliminated, and the magnetofluid hydraulic medium returns to a lower viscosity state, so that the viscous resistance on starting can be reduced, and the starting performance of the hydraulic cylinder is facilitated.

(2) Buffering principle of rod cavity: the nanometer magnetic fluid hydraulic medium with pressure enters the rodless cavity of the hydraulic cylinder from the rodless cavity oil port 12 to push the piston 8 to move towards the rod cavity cylinder cover 2, the hydraulic medium in the rod cavity flows through the rod cavity buffer cavity 5, and flows out of the rod cavity oil port 3 and returns to the oil tank. Along with the movement of the piston 8 to the rod cavity cylinder cover 2, the rod cavity buffer head 7 is gradually close to the rod cavity buffer cavity 5, when the rod cavity buffer head 7 is inserted into the rod cavity buffer cavity 5, a radial gap is formed between the rod cavity buffer head 7 and the rod cavity buffer cavity 5, the through-flow sectional area of the hydraulic medium is instantly reduced, the through-flow resistance of the hydraulic medium is increased, and the effect of blocking the movement of the piston 8 is formed. Meanwhile, the electromagnet 4 is electrified to generate a magnetic field as shown in fig. 5, the viscosity of the nano magnetic fluid hydraulic medium is increased under the action of the magnetic field, and a high-viscosity area is formed in the buffer cavity, so that the through-flow damping coefficient is increased, the resistance borne by the piston cylinder is increased, and the vibration caused by the variable through-flow section is absorbed. Under the variable cross-section throttling and viscosity regulating effects, the piston 8 is decelerated by a large and stable damping force, so that a buffering effect is achieved. When the piston 8 reaches the terminal, the electromagnet 4 is powered off, the magnetic field is eliminated, and the magnetofluid hydraulic medium returns to a lower viscosity state, so that the viscous resistance on starting can be reduced, and the starting performance of the hydraulic cylinder is facilitated.

2. Principle of sealing and lubrication

(1) The micro-magnetic array sealing and lubricating principle is as follows: as shown in fig. 3, when the piston is at rest or runs at a low speed after being started, the nano-magnetic fluid hydraulic medium is acted by the magnetic field of the micro-magnetic array 9-2, the viscosity is increased, a high-viscosity lubricating film is formed in the micron-sized sealing gap, leakage of the hydraulic cylinder under the low-speed heavy load is avoided, and the control precision of the hydraulic cylinder under the low-speed heavy load is improved. When the piston moves at a high speed, the leakage is reduced by utilizing the pressure equalizing effect of the miniature circular groove 9-1, and meanwhile, the pressure equalizing effect of the miniature circular groove 9-1 is coupled with the nano magnetic fluid high-viscosity lubricating film to form oil film lubrication, so that the antifriction effect is achieved, and the high-speed lubricating characteristic of the gap is improved.

The Halbach magnetizing scheme has the performance characteristics that: compared with the common magnetizing scheme, the Halbach magnetizing scheme comprises the following steps: (1) the magnetic energy can be concentrated on the upper side, and the magnetic energy is utilized to a greater extent. (2) Because the magnetic particles in the nano magnetic fluid are arranged along the direction of the magnetic induction lines on the microcosmic scale, compared with the common magnetizing scheme, the gap magnetic induction lines after Halbach magnetizing are more continuously distributed, so that the nano magnetic fluid lubricating film has the continuous and stable lubricating characteristic.

While the present invention has been described in detail with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, and various changes can be made without departing from the spirit and scope of the present invention.